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Abstract: Yield differences among wheat cultivars and its responsiveness to resource availability are usually related to grain number per m2, and further increases in grain number are required, but now beyond differences in time to anthesis and plant height (that are mostly optimised in traditional growing regions). The objective of this paper was to determine and quantify differences in yield physiology between different modern well adapted durum wheats grown in contrasting conditions (in addition we also tested if a higher amount of resources due to removal of competition could affect yield through the same determinants to nitrogen (N) availability). Four experiments were carried out during two growing seasons (2008–09 and 2009–2010); all in all under eight different growing conditions (Gc1–Gc8). In the first season four different modern cultivars were used and in the second season we selected the two highest-yielding cultivars, which differed in their responses to N in terms of spike fertility. Yield was closely related to biomass and N uptake due to both growing conditions and genotypic effects in all experiments. The existence of variation among modern cultivars in these yield determinants is relevant as further increases in yield must be achieved beyond further increases in partitioning. Yield differences among cultivars were based on their differences in grains per m2 or average grain weight depending on which cultivars were compared. Overall grain number was related to spike dry weight at anthesis, and no evidences were found for a direct involvement of N in grain number determination, beyond the general effect of N availability on spike dry matter. However, this overall effect was mainly driven by growing conditions whilst differences between genotypes seemed associated with either spike dry weight at anthesis or fruiting efficiency, which varied significantly between cultivars. Interestingly, grain weight was consistently higher in the cultivars with lower fruiting efficiency than in cultivars maximising the number of grains set per unit of spike dry weight at anthesis suggesting a constitutive component for the commonly reported negative relationship between grain weight and grain number. In conclusion, the main differences in yield between modern, well adapted wheats were related to their biomass and N uptake and to the sink-strength during post-anthesis, being this strength increased either by having more grains or grains of potentially greater size, depending on the specific cultivar and as a consequence of a trade-off between fruiting efficiency and grain size. [Copyright &y& Elsevier]

Abstract: Previous work with crops used for livestock forage and grain production has shown that crop regrowth after grazing is influenced by grazing pressure, shoot dry matter (DM) removed and rainfall, though such findings are typically obtained using limited growing seasons. The aims of this paper were four-fold: (1) validate a wheat-grazing crop model (WHTGRAZ), (2) determine the effect of grazing regime on grain yield at the same grazing pressure, (3) determine the relationship between grazing intensity, yield and rainfall, and (4) determine how shoot DM at the start of grazing influences total DM consumption and grain yield. The ability of WHTGRAZ to predict post-grazing shoot DM accumulation was as good as or better than its ability to predict that of ungrazed crops. Aims 2–4 were investigated by simulating grazing while crops were vegetative. When the number of grazing days per hectare was predefined, yield of crops subjected to light grazing intensities for long periods were similar to yields of crops subjected to high grazing intensities for short periods. When the number of grazing days per hectare was unlimited and grazing was terminated only upon reaching a minimum shoot DM or maximum development stage, more grazing was obtained with lower grazing intensities. Irrespective of grazing intensity, crop yields were generally equal to or greater than those of ungrazed crops in years when growing season rainfall was low, but the converse occurred when growing season rainfall high. In very wet years, delaying the start of light intensity grazing decreased total shoot DM consumption and increased yield. Alternatively, delaying the start of high intensity grazing increased shoot DM consumed and decreased yield. Two major conclusions were deducted from this study. First, grazing of rainfed wheat at relatively light intensities for long durations allows more regrowth to occur during the grazing interval. This both increases removal of shoot DM and is less likely to penalise yield. Second, the probability of grazing increasing crop productivity is greatest in years with low rainfall, regardless of grazing intensity. [Copyright &y& Elsevier]

Abstract: Existing crop-livestock models can largely be separated into two groups: those that simulate crop growth and grain yield with no grazing, and those that simulate pasture production during and after grazing but do not simulate grain yield. The purpose of this paper was to develop a crop-grazing model (hereafter, ‘WHTGRAZ’) capable of realistically simulating biophysical phenomena of grazed wheat crops in rainfed environments. This derivation revealed important physiological distinctions between typical crop simulation and changes in growth that occurred as a result of grazing, such as delayed phenological development. WHTGRAZ was based on the crop model SUCROS2, with modifications. The Penman approach to evapotranspiration simulation was adapted to the FAO Penman–Monteith method. Dry matter (DM) accumulation was modified from photosynthesis to radiation-use efficiency. Specific leaf area was modelled as a function of crop ontogeny, and rules for dead leaf decomposition and trampling of shoot DM were also added. Phenological delays induced by defoliation – and consequences thereof – were identified as a key determinant of growth after grazing, and were modelled as a function of temperature and the rate of shoot DM removal. Parameters were calibrated using measurements of phenology, soil water, shoot DM, and leaf area index from field experiments using two winter wheat cultivars and four grazing treatments. Two important physiological insights were gained from the derivation. First, accurate prediction (within one SEM) of shoot DM removal during grazing is a necessary prerequisite for accurate simulation of post-grazing shoot DM accumulation. Reasonable quantification of green leaf removal and trampling by livestock is needed because green leaf area governs light interception and growth in WHTGRAZ. Second, grazing-induced delays to phenological development cause greater proportions of shoot DM to be allocated to leaves during late vegetative development, decreasing the fraction of shoot DM that would otherwise be partitioned to stems. Delayed phenology of grazed crops also causes greater proportions of kernel DM to be sourced from post-anthesis photosynthesis, as opposed to DM retranslocated from stems. [Copyright &y& Elsevier]

Abstract: Seasonal rainfall in the Philippines is known to be modulated by ENSO phenomenon, with El Niño frequently contributing to reduced rainfall and drought while La Niña resulting in excessive rainfalls, floods and more intense typhoons. The alterations in rainfall patterns can have considerable feedback on solar radiation, air temperature, and soil moisture which can affect the ecosystem CO2 exchange. In this paper, we assessed the effects of the ENSO events (2008–mid 2010) on the seasonal climate conditions and determined how it affected the gross primary production (GPP), ecosystem respiration (Re), and net ecosystem production (NEP) of two contrasting rice environments: flooded and non-flooded. The 2008 dry season (DS) was under a La Niña event while the 2008 wet season (WS) was a neutral one with strong tropical cyclones associated during the wet season. The 2009DS was also La Niña while the 2009WS was El Niño; however, the northern part of the Philippines experienced strong tropical cyclones. The 2010DS was under an El Niño event. The La Niña in 2008DS resulted in about 15% lower solar radiation (SR), 0.3°C lower air temperature (T a) and 60% higher precipitation compared to the 28-year climate normal patterns. Both flooded and non-flooded rice fields had lower NEP in 2008 DS (164 and 14gCm−2, respectively) than in 2008 WS (295 and 82gCm−2, respectively) because the climate anomaly resulted in SR – driven decrease in GPP. The La Niña in 2009DS even resulted in 0.2°C lower air temperature and 40% more precipitation than the 2008DS La Niña. This cooler temperature resulted in lower Re in flooded rice fields while the higher precipitation resulted in higher GPP in non-flooded fields since the climate was favorable for the growth of the aerobic rice, the ratoon crops and the weeds. This climate anomaly benefitted both flooded and non-flooded rice fields by increasing NEP (351 and 218gCm−2, respectively). However, NEP decreased in 2009WS in both flooded and non-flooded rice fields (225 and 39gCm−2, respectively) due to the devastating effects of the strong tropical cyclones that hit the northern part of the Philippines. On the other hand, the El Niño event during 2010DS resulted in about 6% higher solar radiation, 0.4°C higher air temperature and 67% lower precipitation than the 28-year climate normal pattern. The NEP of flooded and non-flooded rice fields were closely similar at 187 and 174gCm−2, respectively. This climate anomaly resulted in T a – driven increase in Re, as well as vapor pressure deficit (VPD) – driven decrease in GPP in flooded rice fields. The GPP and Re in non-flooded rice fields were less sensitive to higher VPD and higher T a, respectively. It appears that the net ecosystem CO2 exchange in non-flooded rice field was less sensitive to an El Niño event. [Copyright &y& Elsevier]

Abstract: The objective of this work was to describe the dynamics of senescence of field-grown maize from silking to harvest, at both leaf and plant level. At the leaf level, the dynamics of symptoms of senescence were considered on each leaf taken individually and described according to zones from the tip to the base of the leaf lamina. At the whole plant level, foliar ranks were each considered as an entity to describe the time course of senescence. To this end, we use a database built-up from field trials conducted during three consecutive years (1994–1996) and thus undergoing variable meteorological and soil water conditions. Leaf chlorophyll content was estimated using two different methods based on the optical properties of the leaves. In Trial I, chlorophyll estimates were based on leaf optical density measured with a MacBeth TR-924 densitometer. In Trial II and Trial III, chlorophyll estimations were based on measurement using a hand-held Minolta SPAD-502 device. In Trial II and Trial III, chlorophyll fluorescence analyses under filed conditions were performed. These analyses focused on the photosystem II (PSII) maximum efficiency (Fv′/Fm′) parameter in the light-adapted state. Measurements were done with a Waltz PAM-2000 portable fluorometer. We report detailed descriptions of the spatio-temporal dynamics of these indicators of senescence. We found that, after silking, a strong relationship exists between available water and leaf chlorophyll content. Further, the maximum efficiency of PSII decreased faster in maize plants undergoing low available soil water than in irrigated plants. The rank of a leaf is determinant of the time for the beginning of the decline in both chlorophyll content and maximum efficiency of PSII. At plant and leaf level, the onset of senescence was marked by a decrease in chlorophyll content that was not concomitant with a dramatic decrease in the maximum efficiency of PSII. Our analyses suggest that a non-linear functional relationship could exist between these two parameters during monocarpic senescence. In the mean time, the results presented in this paper could be used to refine the senescence related modules in plant and crop models. [Copyright &y& Elsevier]

Abstract: Over the past 3 decades, the study of various mechanisms involved in maize grain yield (GY) formation and its relationship with nitrogen (N) uptake dynamics has been increasingly acknowledged in the scientific literature. However, few studies have combined investigations of GY response to N fertilizer with detailed physiologically based analyses of plant N dynamics such as N uptake quantities, timing, and (or) partitioning – and the complex interactions of those with specific genotypes (G), management practices (M), and (or) production environments (E). Limited reporting of both N and yield dynamics at plant-component, individual-plant, and community levels has contributed to a considerable knowledge gap as to whether the physiological mechanisms that govern maize plant N dynamics and their relationship with GY formation have changed with time. We therefore undertook a comprehensive review to discern trends in physiological aspects of maize response to changing plant densities and fertilizer N rates (M components) under the umbrella of evolving G×E interactions. We reviewed 100 published and unpublished papers based on field experiments which consistently reported total plant N uptake at maturity and maize GY (frequently among other physiological variables). Our analyses were limited nearly exclusively to experiments involving hybrid (as distinct from inbred) response to M input levels where plant density data was available. Dissection of the complex interactions among years, plant densities and N rates began with division of treatment mean data (close to ∼3000 individual points) into two time periods defined by year(s) of the original research: (i) studies from 1940 to 1990 – “Old Era” and, (ii) studies from 1991 to 2011 – “New Era”. For the Old Era, maize GY averaged 7.2Mgha−1 at a mean plant density of 5.6plm−2 with a total plant N uptake of 152kgNha−1, a grain harvest index (HI) of 48% and N harvest index (NHI) of 63%. For the New Era, maize GY averaged 9.0Mgha−1 at a mean plant density of 7.1plm−2, total plant N uptake of 170kgNha−1, a grain HI of 50% and a NHI of 64%. The most striking findings in terms of overall GY and plant N uptake were: (1) on a per-unit-area basis, both potential GY and NIE (GY/N uptake) increased from Old to New Era at comparable N uptake levels, and (2) on a per-plant basis, total plant N uptake at maturity had not changed between Eras despite increased plant density in the New Era genotypes. Other important findings in terms of plant growth and component partitioning responses to N were (i) a consistently strong dependency between dry matter and N allocation to the ear organ in both Eras; (ii) higher total plant biomass (BM) accumulation and N uptake, on an absolute basis, during the post-silking period with New Era genotypes accompanied by relatively smaller changes in HI and NHI; (iii) a strong correlation between plant N uptake at silking time and per-plant GY and its components in both Eras; (iv) New Era (56.0kg GYgrainkg−1 N) was primarily associated with reduced grain %N, and to a minor degree with NHI gains; and (v) New Era genotypes showed higher tolerance to N deficiency stress (higher GY when no N fertilizer was applied), and larger GY response per unit of N applied, relative to Old Era hybrids. This improved understanding of the physiological factors underlying progress in maize yield response to N over time, within the context of changing G×E×M factors, serves to help guide maize programs focused on achieving further improvements in N use efficiency. [Copyright &y& Elsevier]

Abstract: In this study, the performance of nine widely used and accessible crop growth simulation models (APES-ACE, CROPSYST, DAISY, DSSAT-CERES, FASSET, HERMES, MONICA, STICS and WOFOST) was compared during 44 growing seasons of spring barley (Hordeum vulgare L.) at seven sites in Northern and Central Europe. The aims of this model comparison were to examine how different process-based crop models perform at multiple sites across Europe when applied with minimal information for model calibration of spring barley at field scale, whether individual models perform better than the multi-model mean, and what the uncertainty ranges are in simulated grain yields. The reasons for differences among the models and how results for barley compare to winter wheat are discussed. Regarding yield estimation, best performing based on the root mean square error (RMSE) were models HERMES, MONICA and WOFOST with lowest values of 1124, 1282 and 1325 (kgha−1), respectively. Applying the index of agreement (IA), models WOFOST, DAISY and HERMES scored best having highest values (0.632, 0.631 and 0.585, respectively). Most models systematically underestimated yields, whereby CROPSYST showed the highest deviation as indicated by the mean bias error (MBE) (−1159kgha−1). While the wide range of simulated yields across all sites and years shows the high uncertainties in model estimates with only restricted calibration, mean predictions from the nine models agreed well with observations. Results of this paper also show that models that were more accurate in predicting phenology were not necessarily the ones better estimating grain yields. Total above-ground biomass estimates often did not follow the patterns of grain yield estimates and, thus, harvest indices were also different. Estimates of soil moisture dynamics varied greatly. In comparison, even though the growing cycle for winter wheat is several months longer than for spring barley, using RMSE and IA as indicators, models performed slightly, but not significantly, better in predicting wheat yields. Errors in reproducing crop phenology were similar, which in conjunction with the shorter growth cycle of barley has higher effects on accuracy in yield prediction. [Copyright &y& Elsevier]

Abstract: The shift to agricultural systems involving no-tillage from those based on multiple cultivations has required decades and is ongoing. This paper examines the enabling factors for the adoption of no-tillage cropping systems including the demand-induced innovation by farmers and agricultural engineers, enabling agronomic technologies such as herbicides and crop disease resistance, extension processes, and economic influences. The first section draws upon existing studies from grain producing regions to demonstrate the multiple dimensions and lags involved in achieving such a major change in agricultural practice. In the second section, we identify and quantify the major agronomic and socio-economic drivers of no-tillage adoption rates in Australia. Analysis of data collected from 1170 grain growers across 19 Australian grain growing regions is used to characterise current no-tillage adoption by regions and the its extent of use. Cumulative adoption curves show that the proportion of farmers using at least some no-tillage has started to plateau near 90% in several regions, while in others, a much lower proportion of farmers have adopted or expect to adopt in the medium term future. Many Australian growers use some no-tillage but maintain a high degree of flexibility in their approach to soil disturbance and respond to economic and seasonal drivers. The results suggest that the same extension and diffusion processes that have led to the current high adoption by farmers in some regions may not lead to further adoption of no-tillage in all regions. Soil erosion, for example, was an important motivating factor early in the development of no-tillage but is not found to be a major factor differentiating adopters and non-adopters in the later stages of technology diffusion. Increasingly, the constraint to more extensive use of no-tillage is the extent of use by existing adopters. Factors relating to disease risks and weed management are identified as important. The long and knowledge intensive innovation process for no-tillage systems has led to remarkable changes in agricultural landscapes. It is an ongoing process that continues in later-adopting regions and in sustaining extensive use. [Copyright &y& Elsevier]

Abstract: Conservation Agriculture (CA) is being advocated to enhance soil health and sustain long term crop productivity in the developing world. One of CA''s key principles is the maintenance of soil cover often by retaining a proportion of crop residues on the field as mulch. Yet smallholder crop–livestock systems across Africa and Asia face trade-offs among various options for crop residue use. Knowledge of the potential trade-offs of leaving more residues as mulch is only partial and the objective of this research is to address some of these knowledge gaps by assessing the trade-offs in contrasting settings with mixed crop–livestock systems. The paper draws from village surveys in 12 sites in 9 different countries across Sub-Sahara Africa and South Asia. Sites were clustered into 3 groups along the combined population and livestock density gradients to assess current crop residue management practices and explore potential challenges to adopting mulching practices in different circumstances. Results show that although high-density sites face higher potential pressure on resources on an area basis, biomass production tends to be more substantial in these sites covering demands for livestock feed and allowing part of the residues to be used as mulch. In medium-density sites, although population and livestock densities are relatively lower, biomass is scarce and pressure on land and feed are high, increasing the pressure on crop residues and their opportunity cost as mulch. In low-density areas, population and livestock densities are relatively low and communal feed and fuel resources exist, resulting in lower potential pressure on residues on an area basis. Yet, biomass production is low and farmers largely rely on crop residues to feed livestock during the long dry season, implying substantial opportunity costs to their use as mulch. Despite its potential benefit for smallholder farmers across the density gradient, the introduction of CA-based mulching practices appears potentially easier in sites where biomass production is high enough to fulfil existing demands for feed and fuel. In sites with relatively high feed and fuel pressure, the eventual introduction of CA needs complementary research and development efforts to increase biomass production and/or develop alternative sources to alleviate the opportunity costs of leaving some crop residues as mulch. [Copyright &y& Elsevier]

Abstract: Low inherent fertility of tropical soils and degradation, nutrient deficiency and water stress are the key factors that hamper rainfed agriculture in semi-arid West Africa. Conservation Agriculture (CA) is currently promoted in the region as a technology to reduce soil degradation, mitigate the effect of droughts and increase crop productivity while reducing production costs. CA relies on the simultaneous use of three practices: (1) minimum or zero-tillage; (2) maintenance of a permanent soil cover and; (3) diversified profitable crop rotation. The most prominent aspect of CA for degraded lands in the semi-arid tropics would be the organic soil cover that impacts on the soil water balance, biological activity, soil organic matter build-up and fertility replenishment. Yet, the organic resources are the most limiting factor in Sahelian agroecosystems due to low biomass productivity and the multiple uses of crop residues, chiefly to feed the livestock. Hence, CA as such may hardly succeed in the current Sahelian context unless alternative sources of biomass are identified. Alternatively, we propose: (1) to gradually rehabilitate the biomass production function of the soil through increased nutrient input and traditional water harvesting measures that have been promoted as “soil and water conservation” technologies in the Sahel, e.g. zaï, in order to restore soil hydrological properties as prerequisite to boosting biomass production; (2) to encourage during this restorative phase the regeneration of native evergreen multipurpose woody shrubs (NEWS) traditionally and deliberately associated to crops and managed the year around and; (3) to shift to classical, less labour intensive CA practices once appropriate levels of soil fertility and water capture are enough to allow increased agroecosystem primary productivity (i.e., an active ‘aggradation’ phase followed by one of conservation). The CA systems we propose for the Sahelian context are based on intercropping cereal crops and NEWS building on traditional technologies practiced by local farmers. Traditionally, NEWS are allowed to grow in croplands during the dry season; they reduce wind erosion, trap organic residues and capture the Harmattan dust, influence the soil hydraulics and favour soil biological activity under their canopies. They are coppiced at the end of the dry season, leaves and twigs remain as mulch while branches are collected for domestic fuel and other uses. Shoots re-sprouting during the rainy season are suppressed as weeds. Such CA systems have limited competition with livestock due to the poor palatability of the shrub green biomass, which may increase their acceptance by smallholders. Such aggradation–conservation strategy is not free of challenges, as it may imply initial soil disturbance that entail important labour investments, substantially change the structure and management of the cropping system (annual crop-perennial plant), and lead to emerging tradeoffs in the use of resources at different scales. This paper offers a state of the art around NEWS and their integration in relay intercropping CA systems, discusses the above mentioned challenges and the main research needs to address them. [Copyright &y& Elsevier]

Abstract: Rainfed and irrigated agricultural systems have supported livelihoods in the five Central Asian countries (CAC) for millennia, but concerns for sustainability and efficient use of land and water resources are long-standing. During the last 50 years, resource conserving technologies were introduced in large parts of the rainfed areas while the irrigated areas were expanded largely without considering resource conservation. In more recent years, the use of conservation agriculture (CA) practices has been reported for the different agricultural production (AP) zones in CAC, albeit centering on a single AP zone or on single factors such as crop yield, implements or selected soil properties. Moreover, conflicting information exists regarding whether the current practices that are referred to as ‘CA’ can indeed be defined as such. Overall information on an application of CA-based crop management in Central Asia is incomplete. This discussion paper evaluates experimental evidence on the performance of CA and other resource conserving technologies in the three main AP zones of CAC, provides an overview of farmer adoption of production practices related to CA, and outlines technical and non-technical challenges and opportunities for the future dissemination of CA practices in each zone. Agronomic (e.g. implements, crop yields, duration, and crop residues), institutional (e.g. land tenure) and economic (e.g. short vs. long-term profitability) perspectives are considered. At present, adoption of CA-based agronomic practices in the rainfed production zone is limited to partial crop residue retention on the soil surface or sporadically zero tillage for one crop out of the rotation, and hence the use of single CA components but not the full set of CA practices. In the irrigated AP zones, CA is not commonly practiced and many of the pre-conditions that typically encourage the rapid spread of CA practices appear to be absent or limiting. Further, our analysis suggests that given the diversity of institutional, socio-economic and agro-ecological contexts, a geographically differentiated approach to CA dissemination is required in the CAC. Immediate priorities should include a shift in research paradigms (e.g. towards more participatory approaches with farmers), development of commercially available reduced and no-till seeders suitable for smaller-scale farm enterprises, and advocacy so that decision makers understand how different policies may encourage or discourage innovations that lead towards more sustainable agricultural intensification in the CAC. [Copyright &y& Elsevier]

Abstract: Cover crops have been successfully integrated into conservation agriculture systems in many parts of the world. They are primarily used to provide surface cover as well as to improve soil fertility and suppress weeds. Black oat (Avena strigosa Schreb.) is a widely used cereal cover crop with a rapid growth and high biomass production. It is being trialled as a cover crop for conservation agriculture systems in south-western Australia, which has a Mediterranean climate with a short winter growing season and where terminal drought is common. Only one crop can be grown in a year and, as such, the long term benefits of including a cover crop in this system must outweigh the loss in income by not growing a cash crop. This study, which was part of a larger conservation agriculture cropping systems trial, examined the effect of different crop sequences, which included oat cover crops and grass pasture, on soil nitrogen mineralisation and weed control. A related paper in this Special Issue examined the effect of cover crops on the soil water balance. We hypothesised that the inclusion of high-biomass oat cover crops in a cereal-dominated cropping system would (i) result in less immobilisation of soil nitrogen compared with that of harvested cereals, and (ii) significantly improve the weed control. We show that soil N mineralisation following oat cover crops was similar to that following wheat and barley. Therefore, cash crops grown after oat cover crops would require similar levels of nitrogen to those grown after harvested cereals. Oat cover crops and grass pasture were found to be very effective in controlling weeds, even in continuous cereal rotations. Two consecutive years of cover crop were required for good annual ryegrass (Lolium rigidum Gaud.) control in a predominantly cereal rotation. Timing of when the cover crops were killed by herbicide was crucial for good weed control, as failure to prevent weed seed set resulted in significantly reduced weed control. Also, late killing of the cover crop reduced soil water storage. The inclusion of an oat cover crop in the rotation reduced the three-year average gross margin; however, the profitability of these crops needs to be evaluated over a longer period. To date, managed pasture, with herbicide control of weed seed set, appears to be a better option than oat cover crops because of the relatively low cost and increased soil water storage. [Copyright &y& Elsevier]

Abstract: Modern conservation agriculture practices aim to maintain year-round ground cover in order to maximise soil protection from extremes of temperature and minimise erosion risk. However, in Mediterranean-style environments with hot dry summer periods, maintaining ground cover can be difficult, as these periods are generally too arid for plant growth. In this research, we investigated the use of cover crops, grown solely to increase ground cover and not harvested for grain or biomass, in a Mediterranean climate. Specifically, we examined the impact of cover crops and residue retention on evapotranspiration, both over the summer fallow period and during the winter and spring crop growth period, and on deep drainage from subsequent crops, on two contrasting soil types in south-western Australia. The impact of cover crops on weed populations and nitrogen dynamics is described in a companion paper. In contrast to previously published research, cover crops and residue retention were found to have limited impact on total evaporation during the summer and autumn period, although there were occasional short-term impacts on the rate of evaporation shortly after rainfall. There was also limited evidence of changes in evaporation during early crop growth. Drainage from crops grown after cover crops was not consistently different to drainage from crops grown after conventional crops. The inclusion of cover crops in farming systems in regions with a Mediterranean climate is unlikely to have major impacts on the water balance, but may still increase overall sustainability of the farming system. [Copyright &y& Elsevier]

Abstract: In the Mediterranean region, conservation agriculture principles like minimum soil disturbance or retaining residues on soil surface are rarely applied in irrigated annual cropping systems. This paper compares a conservation agriculture practice, permanent bed planting (PB), with a conventional system in which the ridges are reformed annually (CB). Comparisons were made throughout a crop sequence of cotton (Gossypium hirsutum L)–maize (Zea mays L.) – cotton in which PB was introduced before the maize cropping. Traffic was controlled during the study. Both maize and cotton crops produced higher leaf area index and biomass under PB than CB and 8 and 24% higher yield respectively though the yield benefit for maize was not significant. The PB system did not improve Water-use Efficiency but delayed water use until the later growth stages. Soil organic matter (SOM) was significantly higher in PB compared to CB one year after the introduction of the system, and this difference was due to higher SOM in the 0–0.05m layer, particularly in the furrows. The lack of negative effects of PB on yield and the positive effects on SOM, coupled with increased water infiltration and reduced erosion shown in previous studies, point to the beneficial adoption of PB in the region assuming the patterns are confirmed in the longer term. [Copyright &y& Elsevier]

Abstract: Maize responses to individual management factors have been widely investigated but studies of higher-order interactions involving multiple factors are rare. This paper investigates the responses of grain yield and water use efficiency of rainfed maize to sowing date, stubble condition, hybrids of contrasting cycle length, soil depth and their interactions, and how these responses are affected by El Niño – Southern Oscillation (ENSO) phenomenon. Grain yield and water balance were modelled with CropSyst using 33 years of weather data for eight locations in an east–west transect in the Southern Pampas of Argentina. Modelled grain yield decreased westward, in parallel with decreasing rainfall. Southern Oscillation Index (SOI) discriminated crop season rainfall and grain yield, with lower rainfall and grain yield for SOI phase Consistently Positive (CP) and higher rainfall and grain yield for SOI phase Consistently Negative (CN). Differences in grain yield between stubble and bare soil were constant across location. High available water, as related to soil depth, increased grain yield across the transect. The effect of sowing date and stubble varied with SOI phase; for CN, highest grain yields were obtained with early sowing whereas for CP grain yield showed no correlation with sowing date. Yield differences between bare soil and stubble conditions were higher under CP than under CN, reflecting the positive effect of stubble in years with rainfall below average. Water use efficiency (WUE=yield per unit evapotranspiration) averaged 19.0kgha−1 mm−1 for soils with stubble and 16.5kgha−1 mm−1 for bare soil. We conclude that SOI provides an agronomically meaningful predictor of seasonal conditions that can be used to estimate crop production and manage risk by adjusting key management practices. [Copyright &y& Elsevier]

Abstract: Sclerotinia stem rot caused by the fungus Sclerotinia sclerotiorum is one of the most damaging and difficult-to-manage diseases of oilseed rape (Brassica napus) and mustard (B. juncea). Identifying oilseed Brassica genotypes with effective resistance offers the best long-term prospect for improved management of the disease. Despite some significant interactions between oilseed Brassica genotypes and S. sclerotiorum isolates reported in earlier studies, mostly a single pathogen isolate has been used to identify resistant genotypes. This paper reports the results of studies involving 53 isolates of S. sclerotiorum from the northern and southern agricultural regions of Western Australia where Sclerotinia stem rot is a serious disease of oilseed rape. Colony characteristics of isolates on potato dextrose agar were determined, and two field virulence (i.e., levels of disease severity) studies conducted. The first field study included 14 Brassica genotypes against three S. sclerotinia isolates and the second had eight Brassica genotypes against 50 S. sclerotinia isolates. Only colony diameter of isolates growing on potato dextrose agar was correlated with stem lesion length in the field. In both field experiments, there were significant effects of isolates and host genotypes, as well as a significant interaction between isolates and genotypes in relation to stem lesion length. In the first field experiment, mean stem lesion length ranged from 1cm in the highly resistant B. napus ZY006 to at least 9cm for susceptible genotypes Brassica juncea #2 and B. juncea Montara. The latter genotype was the most susceptible with a mean stem lesion length of 11.1. Expression of high-level resistance in B. napus ZY006 was largely independent of S. sclerotiorum isolate. In contrast, responses in B. napus genotypes, Zhongyou 821, 06-6-3792, RT108 and Charlton were much more isolate-dependent. In the first field experiment, with a greater number of host genotypes than S. sclerotiorum isolates, a higher variance ratio occurred for isolates (VR=158.4) than for host genotypes (VR=10.7). In the second field experiment, with a larger number of S. sclerotinia isolates than hosts, host genotypes had a higher variance ratio (VR=458.9) compared to the isolates (VR=71.2). Increasing the number of isolates greatly improved the capacity to differentiate levels of resistance among test genotypes. In this experiment, some genotypes showed more consistent resistant reactions (e.g., B. napus Mystic and B. juncea Xinyou 9) across different isolates and these are ideal targets for commercial exploitation of this resistance in oilseed Brassica breeding programs. From this experiment, a standardized set of three B. napus and three B. juncea genotypes were shown to be suitable for use as universal differentials to characterize pathotypes of S. sclerotiorum using octal nomenclature. Eight distinct pathotypes of S. sclerotiorum were delineated and characterized and these six host differential genotypes can now be utilized to identify and monitor the incidence and distribution of current and future pathotypes of S. sclerotiorum. Further, by providing a reliable means to characterize pathotypes of S. sclerotiorum, for the first time not only allows identification of resistance(s) against the predominant pathotype(s) of S. sclerotiorum prevailing in a particular region, but also now allows oilseed rape breeding programs to combine host resistances against several specific pathotypes of S. sclerotiorum into future cultivars. [Copyright &y& Elsevier]

Abstract: Dry spells during the summer period affecting water uptake and plant growth in central Europe may occur more frequently in the future due to climate change. Improving the ability of crops to take up water from deeper soil layers is a potential strategy to secure water supply. The objective of this paper is to report on the effect of different preceding fodder crops on root growth and water uptake of spring wheat from the subsoil. Water extraction and root length density during grain filling of spring wheat were observed between anthesis and maturity in six different soil depths (0–15, 15–45, 45–60, 60–75, 75–90 and 90–105cm) and with four different preceding crops: 1 year of fescue (Fes1Y), 2 years of chicory (Chi2Y), 2 years of lucerne (Luc2Y) and 3 years of chicory (Chi3Y). While there was no difference in total water extraction by wheat in the four crop sequences, water extraction from the deepest layer (90–105cm) was significantly higher after 2 years of lucerne (Luc2Y). This was consistent with the root length densities measured in the 90–105 layer, which were 82, 89 and 112% higher in Luc2Y as compared to Fes1Y, Chi2Y and Chi3Y, respectively. Results suggest that lucerne as preceding crop supports deeper rooting and higher rooting density of following spring wheat enhancing access to water in deeper soil layers in response to prolonged dry spells. Effects facilitating root penetration like improved soil structure and higher nitrogen availability after lucerne are discussed. We conclude that suitable crop rotations with lucerne might be a cost-effective adaptation measure to overcome drought stress. [Copyright &y& Elsevier]

Abstract: Wheat–maize double cropping is the most important cropping system on the Hebei Plain and is one of the most important cropping systems in China. In a scenario of greater food demand, and increasing water and rural labour scarcity, it is critical that the annual productivity of the system is improved in water-energy-cost efficient and low carbon ways. Based on farm surveys, this paper benchmarked the performance of wheat–maize double crops on the Hebei Plain during the 2004–2005 season. These farm yields were assessed both against experimental yields collected from on-farm maximum yield trials conducted during the same 2004–2005 season and relative to simulated estimates of the climate-driven potential productivity of the region. The survey of 362 farms in six counties of the Hebei Plain during the 2004–2005 season found wheat yields ranging from 3375kgha−1 to 9000kgha−1 with an overall average yield of 6556kgha−1. Maize yields averaged 7549kgha−1 and ranged from 3375kgha−1 to 11,250kgha−1. The aggregate production for the wheat–maize double crops grown in the 2004–2005 season averaged 14,105kgha−1 across the six counties. This was 72% of the average production (19,586kgha−1) recorded from on-farm trials conducted in each of the six counties and 60% of the simulated average production potential (24,147kgha−1) for the Hebei Plain in the 2004–2005 season. Thus, the annual productivity of the current cropping system could be increased with currently available technologies by 28%, while a yield increase of 42% is possible if farm yields approach the simulated yield potential. Based on farmer interviews and field observations, a number of real and perceived reasons for the current yield gaps in farmers’ fields were recognised. For instance, irrigation at stem-elongation of wheat is a current recommendation, yet only a proportion of the surveyed farmers were able to follow this strategy due to lack of access to shared irrigation facilities. Improving the region''s infrastructure to enable more timely irrigation of crops will be a necessary prerequisite to improved productivity. The results from the farm surveys and on-farm trials indicate that, with current recommended practices, farmers can improve their annual farm productivity and close the current yield gaps. However, the survey identified that increasing system performance and efficiency will require a focus on both agronomic and socio-economic issues. [Copyright &y& Elsevier]

Abstract: This paper examines the idea that plasticity in farm management introduces resilience to change and allows farm businesses to perform when operating in highly variable environments. We also argue for the need to develop and apply more integrative assessments of farm performance that combine the use of modelling tools with deliberative processes involving farmers and researchers in a co-learning process, to more effectively identify and implement more productive and resilient farm businesses. In a plastic farming system, farm management is highly contingent on environmental conditions. In plastic farming systems farm managers constantly vary crops and inputs based on the availability of limited and variable resources (e.g. land, water, finances, labour, machinery, etc.), and signals from its operating environment (e.g. climate, markets), with the objective of maximising a number of, often competing, objectives (e.g. maximise profits, minimise risks, etc.). In contrast in more rigid farming systems farm management is more calendar driven and relatively fixed sequences of crops are regularly followed over time and across the farm. Here we describe the application of a whole farm simulation model to (i) compare, in silico, the sensitivity of two farming systems designs of contrasting levels of plasticity, operating in two contrasting environments, when exposed to a stressor in the form of climate change scenarios;(ii) investigate the presence of interactions and feedbacks at the field and farm levels capable of modifying the intensity and direction of the responses to climate signals; and (iii) discuss the need for the development and application of more integrative assessments in the analysis of impacts and adaptation options to climate change. In both environments, the more plastic farm management strategy had higher median profits and was less risky for the baseline and less intensive climate change scenarios (2030). However, for the more severe climate change scenarios (2070), the benefit of plastic strategies tended to disappear. These results suggest that, to a point, farming systems having higher levels of plasticity would enable farmers to more effectively respond to climate shifts, thus ensuring the economic viability of the farm business. Though, as the intensity of the stress increases (e.g. 2070 climate change scenario) more significant changes in the farming system might be required to adapt. We also found that in the case studies analysed here, most of the impacts from the climate change scenarios on farm profit and economic risk originated from important reductions in cropping intensity and changes in crop mix rather than from changes in the yields of individual crops. Changes in cropping intensity and crop mix were explained by the combination of reductions in the number of sowing opportunities around critical times in the cropping calendar, and to operational constraints at the whole farm level i.e. limited work capacity in an environment having fewer and more concentrated sowing opportunities. This indicates that indirect impacts from shifts in climate on farm operations can be more important than direct impacts from climate on the yield of individual crops. The results suggest that due to the complexity of farm businesses, impact assessments and opportunities for adaptation to climate change might also need to be pursued at higher integration levels than the crop or the field. We conclude that plasticity can be a desirable characteristic in farming systems operating in highly variable environments, and that integrated whole farm systems analyses of impacts and adaptation to climate change are required to identify important interactions between farm management decision rules, availability of resources, and farmer''s preference. [Copyright &y& Elsevier]

Abstract: With increasing interest in retaining crop residues on the soil surface, there is a need to evaluate their short- and long-term effects on crop yield and water and fertilizer requirements. Therefore, research on the interactions between residue and irrigation management on wheat crop performance and water use was initiated, using the dual approach of field experiments and crop modelling. This paper presents the results of a comprehensive evaluation of the APSIM model for its ability to simulate the effects of mulch and water management, and their interactions, for wheat in Punjab, India. The model was evaluated for its ability to predict crop development, grain yield, biomass production over time, soil water dynamics, daily soil evaporation (Es), total evapotranspiration (ET) and water productivity (WPET kgha−1 mm−1), using two years of data from field experiments at Ludhiana, Punjab. The model predicted grain yield adequately, with coefficients of determination (r 2) of 0.91 and 0.81 with and without mulch, respectively, and prediction of total biomass was even better, with r 2 of 0.99 and 0.92. The corresponding absolute RMSE values were 433 and 550kgha−1 for grain yield (means 4100 and 3800kg ha−1) and 300 and 800kgha−1 for total biomass (means 10,200 and 9300kgha−1). However, grain yield was underpredicted (by 600–1000kgha−1) in treatments where the crop was subjected to water deficit stress, even though simulation of soil water dynamics, and the effect mulch on soil water content, was generally very good. The model accurately predicted total crop seasonal evaporation and the effect of mulch; however, daily Es was poorly simulated. APSIM does not attempt to capture the soil temperature driven effect of mulch on crop phenology. The evaluation shows that APSIM is suitable to use for wheat under the conditions of north-west India. However, additional model processes that capture the effects of mulch on crop development and growth, as driven by soil temperature, are needed to help design intensive cropping systems to optimise land and water productivity. The ability to better simulate crop performance under conditions of water deficit is also needed to help determine irrigation management strategies that minimise irrigation input while maintaining yield. [Copyright &y& Elsevier]

Abstract: Of the wheat grown in North-West India the majority is consumed as traditional Indian flat bread (chapatti). Chapatti quality is important to consumers and people are willing to pay more for better quality wheat flour, but farmers do not specifically target quality outcomes as the majority of their wheat is sold with no segregation. For farmers the main objective is to harvest maximum yields, but in the last decade productivity growth for wheat yields has slowed in the areas where the wheat is grown in a double cropping pattern. Nutrient depletion and temperature-related stress are possible causes for this decline in productivity growth. Farmers meanwhile are looking to opportunities to maintain profitability and, with consumers willing to pay a higher price for better chapatti wheat, an opportunity exists for farmers to manage their wheat to improve both the yield as well as quality of wheat. In this paper we evaluate management practices that best achieve high yield and better chapatti quality, and assess the temperature environment for the winter wheat growing season. A step-wise analysis of the long-term temperature trend for sites in NW India showed that mean annual temperature has increased by 0.7–1.0°C during the last decade. Field experiments with wheat varieties (C-306, WH-283, DBW-17, PBW-343, PBW-502, PBW-550, Raj-3765 and WH-1025) were conducted at farmers’ fields under 4 different sequential cropping rotations for the 2007–08 and 2008–09 winter seasons in Haryana (India). C-306 and WH-283 are varieties with excellent chapatti quality but are lower yielding by 15–26% than the more widely grown varieties such as PBW-343 and PBW-502. The replicated experiments involved three sowing times, these being an early sowing (late October to early November, timely sowing (mid November) and a late sowing (early December). A differential response of varieties was observed to sowing time with the yield of C-306 better whereas that of WH-283 and Raj-3765 was poor in early sown conditions. The varieties DBW-17, PBW-343 and PBW-502 were the highest yielding wheat with similar performance under early as well as timely sowing. All the varieties had lowest yield in December sowing. In general, late sowing had lower thousand grain weight but higher protein content. Of the quality measure grain hardness was the only attribute with a consistent positive correlation with chapatti quality. The chapatti score was higher for varieties C-306 and WH-283 compared to the other varieties but grain hardness and chapatti score was not much affected by sowing time. With all varieties included in the analysis there was no correlation between protein and chapatti score, but within an individual variety usually higher protein resulted in a higher chapatti score. There was no association of grain test weight or sedimentation value with chapatti score. From the results shown here it is evident that farmers will be able to manage with variety choice and timely sowing to obtain chapatti quality without losing grain yield benefits. [Copyright &y& Elsevier]

Abstract: Wheat in Haryana (NW India) is grown as a winter crop in an annual sequence with rice, cotton, pearl millet or cluster bean as the main monsoon crops. Higher wheat yields in Haryana are associated with the use of modern varieties, increase in fertiliser use, improved irrigation practice and conservation tillage, and the recommendation to farmers for N fertiliser rates and timing and irrigation practice have an emphasis on optimising yield and input efficiencies. In India the importance to consumers of product quality does exist and, although the market place presently does not actively reward farmers for better quality wheat, the need for creating suitable and targeted marketing opportunities is now recognised. This paper examines aspects of input efficiencies and focuses on combinations of N-fertiliser and irrigation input in wheat crops grown with these four rotations (rice–wheat, cotton–wheat, pearl millet–wheat and cluster bean–wheat). Management practices that optimise grain production as well targeting grain that achieves best chapatti (Indian flat bread) quality are evaluated within a split-plot experiment where 4 irrigation schedule treatments were split with nitrogen management treatments involving a 2-way or 3-way split of N fertiliser. With the rice–wheat system, there were no differences between different split timings of N with grain yield, however with the 3 other wheat systems the 3 way split of N-fertiliser application, with N applied equally at N-fertiliser applied at seeding, early tillering and first node stage, always gave the highest yield. With all 4 rotations the highest protein level was achieved (range 11.8–12.5%) with this 3-way N application split. Grain yield increased in a step-wise manner as additional irrigation was implemented with all rotations and the highest protein outcomes were achieved with the least irrigations. The apparent recovery of N fertiliser applied was similar and highest with the 3-way split, and the 2-way split that did not include a basal N fertiliser application. Different rates of N fertiliser were included in separate experiments using the 3-way split of N application, and with the rice–wheat rotation the GreenSeeker instrument was used to establish the rate for the third application of N. The application of extra N-fertiliser with the non rice–wheat rotations produced no additional grain yield with an increase in the N-fertiliser input beyond 150kgNha−1, although protein and N-content increased incrementally. Grain hardness and chapatti score trended higher with increases in N-fertiliser input but the increases were relatively small. The use of the GreenSeeker instrument with the rice–wheat rotation resulted in N saving of 21–25kgNha−1 with similar grain yield, protein and grain hardness to that provided by using the recommended 150kgNha−1. Where the GreenSeeker was used the apparent recovery was 70–75% compared with 60% with the wheat receiving the recommended 150kgNha−1, suggesting farmers are likely to be over-fertilising their wheat crop. The best yields obtained in these experiments were about 5.5–6.0tha−1 and these yields are consistent with a decade-long attainable yield identified for wheat in rice–wheat rotation for Haryana. If farmers can achieve market recognition for chapatti quality, and with the use of appropriate varieties, then farmers can assume that the best practice outlined here for optimising grain yield with integrated nutrient and soil management will be the same practice that optimises chapatti quality. [Copyright &y& Elsevier]

Abstract: Mathematical models to describe crop–environment interaction on organ scale need to take crop or plant architecture into account. Up to now, architectural plant models are largely descriptive and parameters need to be estimated for each species, cultivar and environment. Required measurements are extensive and time-consuming. Hence investigating morphological patterns and their modulation as a response to environmental conditions may help to reduce measurement efforts and to predict plant architecture in crop models. In this paper, we describe the plasticity of winter wheat – expressed as the dimensions and sizes of leaf blades, sheaths and internodes in relation to their position on a stem – under the climatic conditions of the Paris region. Results are discussed with respect to: (i) genotypic variability, (ii) inter-annual variability, (iii) sowing date and plant population density, (iv) Nitrogen fertilisation and (v) tiller rank. Eight wheat cultivars grown in the same season showed similar patterns of leaf and internodes dimensions in relation to their position on the stem. For the cultivar ‘Soissons’, main stem architecture at flowering was remarkably stable when similar growth conditions were reproduced in the different seasons. Increased plant population density yielded longer juvenile, but shorter adult leaf blades and sheaths. Earlier sowing led to an increase in the number of juvenile phytomers – growing before the onset of stem elongation – on the main stem, whereas the number of adult phytomers was almost identical. Further there were little differences in the size of leaf blades, sheaths and internodes between the main stem and axillary tillers. We found remarkable differences in the size of adult leaf blades and sheaths in different growing seasons, with different timing of nitrogen fertilisation and we discuss decreased availability of nitrogen in the soil in spring as a likely cause. Data presented here can be used to enlarge the understanding of wheat plasticity regarding the regulation of organ size by temperature, light, plant-available nitrogen and size-mediated effects towards a mechanistic modelling of these responses. [Copyright &y& Elsevier]

Abstract: There is growing interest of international markets in differentiated agricultural products from the tropics. Coffee is a tropical crop of relatively high quality, whose value is increasing as consumer demand in developed countries for specialty coffee. Smallholders in emerging markets can benefit by capitalizing on the natural resource variability in their production system and from the knowledge that they have about this variability. The objective of this paper is to illustrate the benefits of systematically targeting management practices by coffee growers to improve attributes of their product. Data from case studies in Colombia and Mexico show statistically significant differences in beverage quality of coffees grown under different production conditions such as slope aspect, varieties, times of harvest, and shade levels. Possible intervention options can be selected by growers in terms of their ease of implementation, the likely improvement of quality that they achieve and the resource intensiveness they require. The conclusion is that optimum management is site specific so that it is not possible to make any blanket recommendations. Using continuous management cycles of implementation, observation, interpretation and evaluation the site specificity provides growers an opportunity to improve management over time to produce a higher quality product. [ABSTRACT FROM AUTHOR]

Abstract: Appropriate benchmarks for water productivity (WP), defined here as the amount of grain yield produced per unit of water supply, are needed to help identify and diagnose inefficiencies in crop production and water management in irrigated systems. Such analysis is lacking for maize in the Western U.S. Corn Belt where irrigated production represents 58% of total maize output. The objective of this paper was to quantify WP and identify opportunities to increase it in irrigated maize systems of central Nebraska. In the present study, a benchmark for maize WP was (i) developed from relationships between simulated yield and seasonal water supply (stored soil water and sowing-to-maturity rainfall plus irrigation) documented in a previous study; (ii) validated against actual data from crops grown with good management over a wide range of environments and water supply regimes (n =123); and (iii) used to evaluate WP of farmer''s fields in central Nebraska using a 3-y database (2005–2007) that included field-specific values for yield and applied irrigation (n =777). The database was also used to quantify applied irrigation, irrigation water-use efficiency (IWUE; amount of yield produced per unit of applied irrigation), and the impact of agronomic practices on both parameters. Opportunities to improve irrigation management were evaluated using a maize simulation model in combination with actual weather records and detailed data on soil properties and crop management collected from a subset of fields (n =123). The linear function derived from the relationship between simulated grain yield and seasonal water supply, namely the mean WP function (slope=19.3kgha−1 mm−1; x-intercept=100mm), proved to be a robust benchmark for maize WP when compared with actual yield and water supply data. Average farmer''s WP in central Nebraska was ∼73% of the WP derived from the slope of the mean WP function. A substantial number of fields (55% of total) had water supply in excess of that required to achieve yield potential (900mm). Pivot irrigation (instead of surface irrigation) and conservation tillage in fields under soybean–maize rotation had the greatest IWUE and yield. Applied irrigation was 41 and 20% less under pivot and conservation tillage than under surface irrigation and conventional tillage, respectively. Simulation analysis showed that up to 32% of the annual water volume allocated to irrigated maize in the region could be saved with little yield penalty, by switching current surface systems to pivot, improving irrigation schedules to be more synchronous with crop water requirements and, as a fine-tune option, adopting limited irrigation. [Copyright &y& Elsevier]

Abstract: Carbon sequestration in tropical soils has potential for mitigating global warming and increasing agricultural productivity. We analyzed 26 long-term experiments (LTEs) in different agro-climatic zones (ACZs) of India to assess the potential and cost of C sequestration. Data on initial and final soil organic C (SOC) concentration in the recommended N, P and K (NPK); recommended N, P and K plus farmyard manure (NPK+FYM) and unfertilized (control) treatments were used to calculate carbon sequestration potential (CSP) i.e., capacity to sequester atmospheric carbon dioxide (CO2) by increasing SOC stock, under different nutrient management scenarios. In most of the LTEs wheat equivalent yields were higher in the NPK+FYM treatment than the NPK treatment. However, partial factor productivity (PFP) was more with the NPK treatment. Average SOC concentration of the control treatment was 0.54%, which increased to 0.65% in the NPK treatment and 0.82% in the NPK+FYM treatment. Compared to the control treatment the NPK+FYM treatment sequestered 0.33MgCha−1 yr−1 whereas the NPK treatment sequestered 0.16MgCha−1 yr−1. The CSP in different nutrient management scenarios ranged from 2.1 to 4.8MgCha−1 during the study period (average 16.9 yr) of the LTEs. In 17 out of 26 LTEs, the NPK+FYM treatment had higher SOC and also higher net return than that of the NPK treatment. In the remaining 9 LTEs SOC sequestration in the NPK+FYM treatment was accomplished with decreased net return suggesting that these are economically not attractive and farmers have to incur into additional cost to achieve C sequestration. The feasibility of SOC sequestration in terms of availability of FYM and other organic sources has been discussed in the paper. [ABSTRACT FROM AUTHOR]

Abstract: Sorghum (Sorghum bicolor (L.) Moench) is the staple crop of Burkina Faso in West Africa where guinea race landraces are grown in low-input cropping systems. National and international breeding programs have had little success in disseminating modern varieties based on high yield potential caudatum or kafir race breeding materials, mostly introduced from other countries. It has been argued that the breeding objectives were not sufficiently oriented towards the farmers’ needs and preferences, and that they did not target the prevailing growing conditions of Burkina Faso. The objectives of the present article are (i) to identify and examine farmers’ selection criteria for sorghum varieties in the Centre-West of Burkina Faso, (ii) to compare these criteria with the breeder''s agronomic observations and standard practices, and (iii) to show how the criteria of both farmers and breeders can be effectively integrated into the early stages of a pedigree breeding program. These objectives take into consideration gender differentiation, consistency of selection criteria and the interrelationship of measured quantitative traits, as well as the impact of these traits and criteria on the final selection. The present paper is based on a pedigree breeding program that was carried out over three years (2001–2003) in two villages of Burkina Faso. Options for integrating farmers’ selection expertise with that of the breeders’ were examined. Participatory selection was initiated with 53 F3/F4 progenies in field trials managed by farmers using rating and voting exercises. The breeders measured and analysed the agronomic data while the farmers evaluated a large number of progenies by means of their three most important selection criteria and a general appreciation. Farmers’ initial choices remained consistent in the selection exercises (voting) performed in subsequent years. The farmers’ methods for defining traits turned out to be more multivariate than the breeders’ formal understanding of these same traits. This was especially so for the criteria of grain quality, earliness, and productivity for which the farmers’ definition encompasses factors such as flour yield and stability across environments. However, rating results between farmer groups were variable. A disagreement between female and male ratings was especially found for the grain quality traits. The results clearly show that farmers can effectively select for traits on the basis of progeny and single plants while pursuing specific agronomic aims such as adaption. Subsequent yield improvement schemes will thus be more efficient in terms of selection intensity related to grain yield. The study is showing the way for breeders to adjust their selection criteria to suit the basic needs of small-scale farmer in semi-arid regions of sub-Saharan Africa. [Copyright &y& Elsevier]

Abstract: Understanding belowground competition of plants requires a simple method for species identification of plant roots. This study investigates Fourier transform infrared (FTIR)-attenuated total reflexion (ATR) spectroscopy followed by cluster analysis for the discrimination of pea and oat roots. Pea and oat plants were grown under various conditions – in moist paper, soil-compost mixture, soil, in the greenhouse and field – to enhance the intra-species variability of their chemical composition. FTIR-ATR spectra of young-to-old roots from four independent experiments were recorded and represent, like a fingerprint, the chemical sample composition such as lipids, proteins, carbohydrates, etc. To group the spectra according to their spectral similarity in a dendrogram, cluster analysis was performed. The experimental approach discriminated pea and oat roots 100% successfully. The perfect discrimination of pea and oat roots, even from intercropped plants, strikingly demonstrates the potential of the method. [ABSTRACT FROM AUTHOR]

Abstract: The proportion of growth allocated to reproductive organs can be an important determinant of yield variation between cultivars and environments. The main aim of this paper was to evaluate the adequacy of a model assuming constancy in partitioning coefficients (PC, the slope of organ weight to total weight relationship) within periods whose limits are associated with phenological phases to describe variation in reproductive growth (including seeds when present) in the Andean seed crop quinoa. A second objective was to analyze the dynamics of panicle and stem growth to advance our understanding of factors determining yield in this species. To do this, we used data from two experiments conducted in 2 years under field conditions in the Argentinean pampas, using four cultivars belonging to the Sea Level Type and adapted to temperate environments, under three densities. Reproductive partitioning followed a bi-phasic pattern; panicle biomass increased gradually until reaching a total biomass value, and then there was an increase in the slope of panicle vs. total aerial biomass relationship. Partitioning coefficients for the initial stage varied between some cultivars and densities in the first year, but not in the second. No significant differences were detected when PCs for the second stage were considered. The start of panicle growth was associated with thermal time to first anthesis (R 2 =0.62) while thermal time to change in partitioning from low to high PC and that to end of flowering were strongly related (R 2 =0.93). Combining data across cultivars, years and densities gave a PC of 0.15 for the initial stage and 0.90 for the second stage. Using these relationships and parameters dynamics of panicle biomass accumulation was predicted satisfactorily in an independent data set for a different environment, confirming the usefulness of a single model approach to describe partitioning across cvs. and environments in this crop. Besides, crop yield estimations improved when compared to those obtained by a seed number estimation model, predictions were only 7.25% lower than observed values compared to −24.5% using a seed number approach. There is a trade-off between final partitioning to reproductive structures (higher in short-cycle cvs.) and total crop biomass, one of the factors contributing to this trade-off being a negative association between the panicle–stem relationship at harvest and duration in thermal time units of stem growth; so, selection for high partitioning rate should be targeted at long duration cvs. within this germplasm. [Copyright &y& Elsevier]

Abstract: Drought is the primary constraint in pearl millet (Pennisetum glaucum) production in the drier semi-arid and arid regions of south Asia and Africa. The traditional landraces from drier regions are good sources of drought adaptation but often lack high yield under near-optimum growing environments. The objective of this paper was to assess whether crosses between landrace populations and elite germplasm can produce hybrids with better grain yield under favourable conditions than landraces, without compromising grain yield under drought. The research evaluated 20 crosses and their nine parents (consisting of landrace-based populations and elite composites) under drought and non-drought conditions. Drought response index (DRI), based on flowering and grain yield measured in drought and non-drought environments, was used to assess drought tolerance. Landrace populations yielded significantly more grain under drought stress than elite composites and crosses and had the highest mean DRI (3.99). In contrast, composites showed maximum sensitivity to drought with significantly negative DRI (−3.64). Adaptation to either drought or high productivity conditions appeared to be associated with different plant types: higher panicle number, lower grain number per panicle, and smaller seed size were associated with drought adaptation; low tillering and greater number of large-sized seeds per panicle were favoured for optimum growing conditions. Crosses yielded significantly better than composites under drought, better than landrace populations under non-drought and had a wide range in drought sensitivity. Around 40% of crosses produced on average 23% higher grain yield than the best landrace under favourable conditions, without compromising grain yield under drought. The results illustrate that hybridization of landrace populations with elite composites can produce germplasm that combines drought tolerance of traditional material with high production potential of elite genetic material. [Copyright &y& Elsevier]

Abstract: Waterlogging and dryland salinity in Western Australia (WA) as well as in many other parts of the world have long been recognized as major constraints to productive pastures and crops. In the late 90s, bed-furrow systems were introduced to waterlogged non-saline land in high rainfall areas of Australia. That resulted in significant yield increases of broad-acre crops through a reduction of the waterlogging. It was expected that yield gains could also be realised on waterlogged and saline land, of which more than 1million ha is present in WA. This paper examines the productivity of crops and pasture of waterlogged and salt-affected land after the implementation of bed-furrow systems. Three sites were selected in the south western Wheatbelt of WA, with different rainfall regimes and with soil salinity ranging from none to extreme. The treatments were: pasture, cropping and raised beds (RB), no-till beds (NTB) and the Control. The distribution of salinity was mapped using an electromagnetic instrument (EM38). Pasture biomass and distribution were obtained from validated multispectral images. Grain yield and distribution were obtained from calibrated yield maps. In 4 of the 12 site-years, grain yields from the bed-furrow systems were statistically significantly compared to the Control. These were mostly associated with the site in the high rainfall region. The pasture biomass declined under the impact of summer and winter grazing and salinity. Bed-furrow systems did, in general, not generate higher grain yields for a given soil salinity compared to the Control. Relative yield - salinity relationships revealed a higher salt tolerance of the various crops compared to criteria published previously. It was also found that the interaction between waterlogging and salinity was not applicable since the timing of both issues did not coincide. Despite the grain yield gains at the high rainfall site using bed-furrow systems, cropping the low-lying salt-affected and potentially waterlogged land carries high risks. Provided these are accepted, growers with access to such land may be able to extend their cropping areas considerably. It is expected that bed-furrow systems are also beneficial in the waterlogged and salt-affected regions where topographical conditions and a precipitation surplus have created such conditions, like in some of the prairie states of North America. [Copyright &y& Elsevier]

Abstract: Improving rice (Oryza spp.) competitiveness against weeds would provide a low-cost and safe tool for an integrated weed management strategy. This paper addresses the underlying causes of tradeoff between yield without weed competition and weed competitiveness. Rice yield or weed biomass under weedy conditions are used as indicators of weed competitiveness. For this analysis, a common database was compiled from the results of 45 concurrent field trials comparing the performance of four to 64 genotypes in weed-free and weedy conditions in Asia, West Africa, North America and Latin America. Cyperus spp., Echinochloa spp. and Eleusine indica were the most frequent dominant weed species, being found in 9, 20 and 7 trials, respectively. Mean relative yield reduction [(yield under weed-free conditions−yield under weedy conditions)/yield under weed-free conditions] across genotypes tested for each trial was defined as weed pressure level. Mean yield without weed competition across genotypes ranged from 1.8 to 11.6tha−1 with mean relative yield reduction from almost 0 to 91%. Correlations for rice yield between weed-free and weedy conditions were generally positive, and significant in 27 trials. The correlations were related to weed pressure level and dominant weed species, but not to ecosystem (upland or lowland) or yield level under weed-free conditions. Relative yield reduction had a more pronounced effect than dominant weed species. Correlation decreased as weed pressure level increased, and became negative when relative yield reduction exceeded 80%, suggesting that different morpho-physiological mechanisms are responsible for high yields under weed-free conditions or severe weed competition. Correlations between rice yield under weed-free conditions and weed biomass varied, giving 17 and 19 for positive and negative ones, respectively. These correlations were related neither to weed pressure level, ecosystem and yield level under weed-free conditions, nor to dominant weed species. These results indicate that correlations between rice yields under weed-free and weedy conditions can be strongly affected by weed pressure level, and, unless severe weed competition occurs, there appears to be no tradeoff between them. Association of morpho-physiological mechanisms with weed competitiveness under conditions differing in weed pressure levels and dominant weed species deserves further investigation. [Copyright &y& Elsevier]

Abstract: Faba bean is a major grain legume widely cultivated in many countries for food and feed purposes. A number of aerial fungi, together with soil-borne pathogens associated with foot and root rot complexes, nematodes, parasitic weeds and viruses may cause severe diseases in faba bean crops. The use of genetic resistance is the most economical and environmentally friendly control method. However, to date no efficient sources of resistance have been described to some diseases, or it is scarce and of complex nature, making necessary the implementation of other control measures. Phenotypic expression of resistance is usually poorly described. As a consequence of this, and of the poorly developed genomic resources available, the genetic basis of resistances is, in most cases, largely unknown. Effectiveness of MAS might soon increase with the adoption of new improvements in marker technology together with the integration of comparative mapping and functional genomics. In this paper we will review and critically discuss current and future strategies on breeding faba bean for disease resistance. [Copyright &y& Elsevier]

Abstract: Successful production of faba bean crops in the presence of a wide range of disease-causing fungi, parasitic weeds, nematodes, insects, mites and other pests depends on the integration of genetic resistance, hygienic management, monitoring of the target organisms and timely application of appropriate chemical and biological treatments. This paper reviews the progress in this area. Arthropod management is still overly reliant on broad-spectrum insecticides for many pests, particularly aphids, but field assessment, tillage, sowing date, plant density and weed control can minimize pest incursions. Crop assessments, bait and pheromone traps and economic thresholds are used to predict and monitor arthropod pest populations, and biological measures (natural enemy conservation and bioinsecticides) and selective chemicals (less harmful to beneficial insects) are also used. Crop hygiene and seed bank demise is critical for management of broomrape, as much of its damage is done before the parasite is visible above ground. Mild herbicide treatments can prevent ripening of broomrape seeds with minimal damage to the faba bean crop. The main diseases caused by fungi, namely rust, ascochyta blight, chocolate spot and downy mildew, all spread rapidly when weather conditions are appropriate. Since these weather conditions are well characterized for each disease, it is possible to intervene strategically by treating with fungicide at times of high risk. Good sources of resistance are available to the key diseases, although few current cultivars are resistant to more than one disease. Root-lesion, stem and root-knot nematodes can cause severe yield losses but several cultivars and breeding lines of faba bean have good resistance to root-lesion nematodes and at least one has resistance to stem nematode and one to root-knot nematode. These groups of nematode species have broad host spectra so attention to rotations is particularly important. Chemical control of nematodes is difficult and biological control is still experimental. Control of the pathogenic fungi and nematodes requires that clean, non-infested seed be used and that the new crop does not get infected from debris and volunteer from the previous crop or adjacent fields. In the presence of continued selection pressure on the pathogens and pests, continued breeding for novel resistance genes, development of new selective chemicals, screening for new biocontrol agents and the design of new management strategies will all be necessary. [Copyright &y& Elsevier]

Abstract: The grain legume (pulse) faba bean (Vicia faba L.) is grown world-wide as a protein source for food and feed. At the same time faba bean offers ecosystem services such as renewable inputs of nitrogen (N) into crops and soil via biological N2 fixation, and a diversification of cropping systems. Even though the global average grain yield has almost doubled during the past 50 years the total area sown to faba beans has declined by 56% over the same period. The season-to-season fluctuations in grain yield of faba bean and the progressive replacement of traditional farming systems, which utilized legumes to provide N to maintain soil N fertility, with industrialized, largely cereal-based systems that are heavily reliant upon fossil fuels (=N fertilizers, heavy mechanization) are some of the explanations for this decline in importance. Past studies of faba bean in cropping systems have tended to focus on the effect of faba bean as a pre-crop in mainly cereal intensive rotations, whereas similar information on the effect of preceding crops on faba bean is lacking. Faba bean has the highest average reliance on N2 fixation for growth of the major cool season grain legumes. As a consequence the N benefit for following crops is often high, and several studies have demonstrated substantial savings (up to 100–200kgNha−1) in the amount of N fertilizer required to maximize the yield of crops grown after faba bean. There is, however, a requirement to evaluate the potential risks of losses of N from the plant–soil system associated with faba bean cropping via nitrate leaching or emissions of N2O to the atmosphere as a consequence of the rapid mineralization of N from its N-rich residues. It is important to develop improved preventive measures, such as catch crops, intercropping, or no-till technologies, in order to provide farmers with strategies to minimize any possible undesirable effects on the environment that might result from their inclusion of faba bean in cropping system. This needs to be combined with research that can lead to a reduction in the current extent of yield variability, so that faba bean may prove to be a key component of future arable cropping systems where declining supplies and high prices of fossil energy are likely to constrain the affordability and use of fertilizers. This will help address the increasing demand by consumers and governments for agriculture to reduce its impact on the environment and climate through new, more sustainable approaches to food production. The aims of this paper are to review the role of faba bean in global plant production systems, the requirements for optimal faba bean production and to highlight the beneficial effects of faba bean in cropping systems. [Copyright &y& Elsevier]

Abstract: Although Cambisols are the predominant soil type in Central Europe, especially in less favoured mountain areas, the long-term sustainability of winter wheat production on such soils has not been examined. In this paper, the yield of winter wheat over 50 years of farmyard manure, N, P and K fertilizer application (12 treatments altogether) was analysed in the Lukavec Crop Rotation Experiment (LCRE), which was established in 1955 in a potato-growing area (mean annual precipitation and temperature 686mm and 6.8°C, respectively). In the unfertilized control, low plant available P, K and Mg concentrations were recorded after 50 years. The annual yield growth (AYG) of grain was negative in the control as well as in low N treatments and positive in the 46kgNha−1 treatment. The mean AYG ranged from 7.1 to 72.8kgha−1 following the application of 46 to 121kgNha−1, respectively. In the first decade of the experiment, the increase in grain yield per 1kg of applied N was 7.3kgha−1 while in the last decade it was 27.1kgha−1. The mean grain yield of long-straw and short-straw varieties was 3.9 and 4.7tha−1, respectively. In the control, the grain yields were 4.3, 3.2 and 2.4tha−1 after root crops, legumes and cereals, respectively. To summarize the 50 years’ results of winter wheat production in the LCRE, grain yield was the most affected by mineral fertilizers, followed by the effect of variety, the preceding crop and farmyard manure application. The long-term sustainability of winter wheat production on low productive sandy-loamy Cambisols can be achieved only by adequate application of N, P and K fertilizers. High year-to-year variation in grain yield stresses the necessity of long-term studies in crop research, which are able to separate real trends from inter-annual fluctuations. [Copyright &y& Elsevier]

Abstract: The objective of this paper was to investigate the influence of different nitrogen (N) application rates to some morphological and physiological features of leaf blades, including leaf thickness, chlorophyll content at different leaf ages and chlorophyll a/b ratios. A paddy field and a cement tank experiments were conducted simultaneously. Rice leaf thickness was measured through a specially developed displacement sensor. Meanwhile, chlorophyll content was estimated using chlorophyll meter (SPAD) and spectrophotometer after ethanol extraction of leaf samples. With the increase of N application, leaf thickness became thinner and chlorophyll a/b ratios decreased. Moreover, the sensitivity of the SPAD readings of the same leaf at different leaf ages to N rates was assessed through coefficients of variation (CV). CV of SPAD readings increased from 8.8% to 21.6% during leaf lifetime, which indicates that SPAD readings became more and more sensitive to nitrogen rates as leaf aged. Therefore, SPAD readings of the lower leaves, which were physiologically older than the upper ones, were more sensitive to nitrogen rates. [Copyright &y& Elsevier]

Abstract: The rice super cultivar ‘Koshihikari’, grown on 37% of the total rice area in Japan, has been a leading cultivar since 1979. It is also grown in the USA and Australia. However, its tendency to lodge makes harvest difficult and reduces grain quality, and the regularity of large-scale typhoons compromises its production nationally. The genetic improvement of Koshihikari against lodging has been an extremely important theme for the past 30 years in Japan. This paper describes the development of a semidwarf form of Koshihikari by the fixing of an allele of the Green Revolution semidwarf gene sd1 via eight recurrent backcrosses. The cultivar, with excellent flavor and high yield, was named ‘Hikarishinseiki’, which means “Bright New Century” (rice cultivar No. 12273; Ministry of Agriculture, Forestry and Fisheries of Japan: MAFF). Hikarishinseiki, with ≥99.8% of the Koshihikari genome, is about 20cm shorter than Koshihikari. DNA monitoring of Hikarishinseiki confirmed its genomic substitution into Koshihikari except for sd1 and a marker-based method to distinguish Koshihikari from Hikarishinseiki was developed. Its flavor (upper medium grade) and quality were the same as those of Koshihikari grown at 10 sites across Japan, but its yield was on average 3% higher (maximum 29% higher at Hyogo) than that of Koshihikari and it was highly resistant to lodging. Hikarishinseiki is the first semidwarf form of Koshihikari registered by MAFF. Some economical impact has been achieved by introducing Hikarishinseiki and it is already notified as a brand rice description in the rice-producing districts of Niigata, Shiga, Tottori, Okayama, Tokushima, and Kochi prefectures. [Copyright &y& Elsevier]

Abstract: Measurements of soil physical properties, root growth and the water content in the subsurface layers of a clay Sodosol soil were carried out to determine why the incorporation of organic amendment (20t/ha) resulted in marked increases in wheat yield in an earlier paper. The incorporation of lucerne or dynamic lifter® pellets at a depth of 30–40cm resulted in an almost doubling of the macroporosity from <10% to >18%, together with reductions in bulk density and the volumetric water content () at −1500kPa, and a 50-fold increase on saturated hydraulic conductivity in this subsurface layer. These changes in physical properties in the 30–40cm deep layer were highly correlated (r values 0.69–0.93, P <0.01) with increased root growth in this layer, and increases in crop yield. The practice of incorporating an organic amendment in the top clay layer of the B horizon in soils where the high density restricts root growth, which is termed ‘subsoil manuring’, shows promise for increasing crop productivity on these soils in the high rainfall zone of southern Australia. [Copyright &y& Elsevier]

Abstract: Several crop simulation models calculate grain yield by assuming that the rate of change of harvest index (δHI/δt) is constant (at rate k) during grain growth. Such behaviour has been identified in many crops, although the literature contains many examples of variations in k. The concept is useful if it approximates the truth in most circumstances, or if departures from both linearity and constancy are predictable from either the environment or the state of the crop. In this paper we examine the hypothesis that much of the variation in k is related to both crop biomass at the start of grain filling (BGF) and the crop growth rate during grain growth (CGF). Calculations using simple partitioning rules indicated that both factors are important. We showed that k increases rapidly as BGF decreases below about 9.0MgDM/ha, but decreases only slowly with increases of BGF above 9.0MgDM/ha. The analysis also showed that the increase in HI with time is quadratic rather than linear. We analysed data from 68 field grown wheat crops with variation in cultivar, location, irrigation, ambient CO2 concentration and sowing dates. These showed an almost three-fold variation in k (0.0058–0.0164day−1). Across all data sets, there was a negative linear relationship (y =0.02−0.0006x, R 2 =0.41, p <0.001) between k and BGF. Overall, these results suggest that some of the variation in k can be accounted for by differences in BGF. We suggest that any model that uses harvest index change as a basis for calculating yield should account, at least, for variations in BGF. [Copyright &y& Elsevier]

Abstract: Narrow-leafed lupin (Lupinus angustifolius L.) is a grain legume well adapted to sandy soils of a Mediterranean climate and is the major grain legume in Australia. Improved herbicide tolerance of lupin cultivars is now considered as top priority by the industry for effective weed management. This paper reports induced mutation by seed mutagenesis in metribuzin-sensitive but anthracnose resistant cv. Tanjil, selection for metribuzin tolerant mutants in the field and evaluation of the tolerant mutants to metribuzin and anthracnose resistance. Two highly tolerant mutants Tanjil-AZ-33 and Tanjil-AZ-55 were identified and they were the first reported metribuzin tolerant mutants. The estimated mutation rate was 2.5×10−5. Tanjil-AZ-33 was six times and Tanjil-AZ-55 was four times more tolerant to metribuzin than the original cultivar Tanjil and they were also more tolerant than the tolerant cv. Mandelup. Tanjil-AZ-33 was the most tolerant lupin germplasm. Disease nursery assessment over 2 years revealed that both mutants also retained anthracnose resistance. Seed yield under irrigation was 4.2t/ha for Tanjil-AZ-33 and 1.9t/ha for cv. Tanjil when the seedlings were treated with metribuzin at 300g/ha at the six-leaf stage. Clearly the mutation process has created new tolerance to metribuzin, but did not alter the anthracnose resistance. The mutant Tanjil-AZ-33 has been used as a parent in the lupin breeding program as a source of both metribuzin tolerance and anthracnose resistance. Seed mutagenesis followed by field selection in M2 proved to be an effective method to develop new tolerance to herbicides. [Copyright &y& Elsevier]

Abstract: Multi-location trials are commonly used to estimate the effects of different explanatory factors on crop yield. Conversely, the analysis of production databases could also be useful for exploring and understanding such effects. These data require flexible and robust methods for dealing with multivariate, non-linear and unbalanced data structures, high-order interactions and missing values. In this paper, we explore the issue of crop yield explanation using a 5-year period (1999–2005) of sugarcane (Saccharum officinarum L.) yield data from Northern Argentina. Using a data mining technique such as classification and regression trees (CART) we show that farm membership (FARM) was among the main splitting factors for total cane per hectare (TCH) cluster variability. Crop class (AGE) was at the second level in the hierarchy and values of AGE higher than 2,5 splitted low and medium from the high TCH clusters. Sugarcane cultivar (VAR) was the most important explanatory factor regarding total sugar per hectare (TSH), and crop class (AGE) was second in importance. In this case, farm membership did not appear among the main splitting factors. The growth period duration, field area and precipitation did not show remarkable importance values for explaining final TCH and TSH values. By-year CART models also showed low values of importance of weather related variables across the years analyzed suggesting that other environmental conditions than precipitation is controlling yearly variation in sugar and cane yield (e.g. radiation, water-use efficiency or temperature regime). The CART analysis developed here is the first systematic analysis for explanatory factors of biomass and sugar content in Argentina''s cane most productive region. However, we believe this methodology could be applicable for a wider geographic area and other sugarcane production regions as well as other cropping systems. Although regression trees provide less formal statistical inference, its results could be added as an additional analytical tool to traditional experimental analyses that use mixed models. Also, they could be useful for elaborating hypotheses and suggest mechanistic studies to test them. [Copyright &y& Elsevier]

Abstract: In wheat, the ability to store and remobilise large amounts of stem water soluble carbohydrates (WSC) to grain constitutes a desirable trait to incorporate into germplasm targeted to regions with frequent terminal drought. The main aim of this paper was to examine the relationships between WSC storage, grain number and grain weight across several environments. A small set of recombinant inbred lines (2–4) contrasting in stem WSC were grown in six field trials where water availability, sowing date and/or N level were manipulated, with line yields ranging from 400 to 850gm−2 across experiments. Biomass, N and WSC concentration (WSCc, mgg−1 dry weight) and amount (WSCa, gm−2) were monitored. A resource-oriented area-based model [Fischer, R.A., 1984. Growth and yield of wheat. In: Smith, W.H., Bante, S.J. (Eds.), Potential Productivity of Field Crops Under Different Environments. International Rice Research Institute, Los Baños, pp. 129–154] and intrinsic rates of organ growth were used to investigate the consequences on grain number of potential competition between spike and stem around flowering. Early sown irrigated trials allowed consistent genotypic discrimination for WSCc and WSCa. High WSC lines had similar or higher yields compared to low WSC lines. High WSC lines had consistently lower grain number m−2 linked to a lower number of spikes and stems m−2, higher individual grain weight under irrigated or more limited conditions, and individual stems with less structural biomass. The changes in plant type associated with the high WSC phenotype, mainly fewer stems and a high individual grain weight, may contribute to its moderate yield advantage despite the lower grain number m−2. A model based on resource capture per unit area around flowering was not sufficient alone to explain the differences between lines in grain number m−2. We propose that linking a resource-based model with additional understanding of controls of crop morphology would improve the prediction of differences in yield components in related genetic material. [Copyright &y& Elsevier]

Abstract: Cover cropping can have various beneficial effects to the cropping system such us the increase of soil nutrient content and weed suppression. In this respect, the species used for covering is of great importance. This paper reports results on the yield and weed control effects in potato crops preceded by different cover crops over a 2-year period (2003 and 2004) in Central Italy (Viterbo). Results were obtained in the frame of a more complex study set up in 2002 where in a 3-year chick-pea/potato/tomato rotation, each crop was preceded by 7 different soil managements: 5 cover crops (rapeseed, Italian ryegrass, hairy vetch, snail medick and subclover)+1 unfertilised weedy fallow (cover crop absent)+1 control (weedy fallow fertilised with mineral N at a rate of 170kgha−1 for potato). Two different weed control regimes in potato were also applied [weed-free crop (1 inter-row hoeing+1 hilling up+manual weeding on the row); mechanical control (1 inter-row hoeing+1 hilling up)]. Cover crops were sown in September and cut and ploughed just before potato planting in March. The potato crops following the cover crops were only fertilised with green manure. Averaged over years, all the cover crops produced more above-ground dry biomass than the weedy fallow (4.79tha−1 on average vs 2.36tha−1). Hairy vetch and subclover accumulated the highest N in the incorporated biomass (169 and 147kgha−1), followed by snail medick (108), rapeseed (99), ryegrass (88) and weedy fallow (47). Rapeseed and ryegrass were the most efficient weed suppressors and had the least proportion of weed biomass (<1%) of the total produced by the cover, while they also reduced weed emergence in the following potato crops (8.8plantsm−2 vs 25.5plantsm−2 with all other cover crops). Following subclover and hairy vetch the potato crop yield was similar to that obtained by mineral N-P-K fertilisation (48.5tha−1 of fresh marketable tubers). Mechanical weed control compared to weed free crop always reduced potato yield and the reduction, averaged over years, was greater in N-P-K mineral fertilised control (−23.6%) and smaller in ryegrass (−7.9%). [Copyright &y& Elsevier]

Abstract: The black earths of Central Europe are an important soils for crop production but sustainability of crop production on such soils has not been examined. In the present paper, yield of winter wheat over 50 years of FYM, N, P and K fertilizer application (12 treatments altogether) was analyzed in the Ivanovice Crop Rotation Experiment (ICRE), established in 1955 on a degraded black earth soil (chernozem). The ICRE is located in a warm (8.4°C mean annual temperature) and moderately dry (556mm mean annual precipitation) sugar beet cropping area. Summarizing 50 years’ results, variety had the largest effect on grain yield followed by the effect of mineral fertilizers, the preceding crop and farmyard manure application. The highest increase in grain yields was recorded after the introduction of short-straw varieties. High year-to-year variability in grain yields was recorded and some fluctuations were consistent with oscillations in the whole Czech Republic. Despite the high fertility of black earth soils in the locality, the mean grain yield in the ICRE was lower than the mean annual yield in the Czech Republic in five cases out of 50 years. The effect of fertilizer treatment on the grain yield was not significant in the first decade (the mean grain yields ranged from 3.4 to 3.8tha−1), but was significant in the fifth decade of the experiment (the mean grain yields ranged from 4.2 in control to 6.6tha−1 in N121P89K102 treatment, respectively). Calculated by linear regression, the annual yield increased by 45.9–89.6kg of grain per ha. The mean yield per 1kg of applied Nha−1 increased by 18.7kg of grain in the fifth decade of the experiment. In unfertilized soil, the concentration of plant-available P, K and Mg was still optimal for winter wheat production even after 50 years without any fertilizer input. The black earth soils in the locality clearly demonstrates a high and long-term stable natural fertility. The results from the ICRE stress the necessity for long-term research in grain yield analysis. [Copyright &y& Elsevier]

Abstract: This paper focuses on the interaction between genotype and environment, a critical aspect of plant breeding, from a physiological perspective. We present a theoretical framework largely based on Bradshaw''s principles of phenotypic plasticity (Adv. Gen. 13: 115) updated to account for recent developments in physiology and genetics. Against this framework we discuss associations between plasticity of yield and plasticity of phenological development. Plasticity was quantified using linear models of phenotype vs environment for 169 wheat lines grown in 6 environments in Mexico, 32 sunflower hybrids grown in at least 15 environments in Argentina and 7 grapevine varieties grown in at least 14 environments in Australia. In wheat, yield ranged from 0.6 to 7.8tha−1 and the range of plasticity was 0.74–1.27 for yield and 0.85–1.17 for time to anthesis. The duration of the post-anthesis period as a fraction of the season was the trait with the largest range of plasticity, i.e. 0.47–1.80. High yield plasticity was an undesirable trait as it was associated with low yield in low-yielding environments. Low yield plasticity and high yield in low-yielding environments were associated with three phenological traits: early anthesis, long duration and low plasticity of post-anthesis development. In sunflower, yield ranged from 0.5 to 4.9tha−1 and the range of plasticity was 0.72–1.29 for yield and 0.72–1.22 for time to anthesis. High yield plasticity was a desirable trait as it was primarily associated with high yield in high-yielding environments. High yield plasticity and high yield in high-yielding environments were associated with two phenological traits: late anthesis and high plasticity of time to anthesis. In grapevine, yield ranged from 1.2 to 18.7tha−1 and the range of plasticity was 0.79–1.29 for yield, 0.86–1.30 for time of budburst, 0.84–1.18 for flowering, and 0.78–1.16 for veraison. High plasticity of yield was a desirable trait as it was primarily associated with high yield in high-yielding environments. High yield plasticity was associated with two phenological traits: plasticity of budburst and plasticity of anthesis. We report for the first time positive associations between plasticities of yield and phenology in crop species. It is concluded that in addition to phenology per se (i.e. mean time to a phenostage), plasticity of phenological development merits consideration as a distinct trait influencing crop adaptation and yield. [Copyright &y& Elsevier]

Abstract: Drought stress is the most important abiotic factor limiting upland rice yields. Identification of quantitative trait loci (QTL) conferring improved drought resistance may facilitate breeding progress. We previously mapped a QTL with a large effect on grain yield under severe drought stress (qtl12.1) in the Vandana/Way Rarem population. In the current paper, we present results from a series of experiments investigating the physiological mechanism(s) by which qtl12.1 affects grain yield under drought conditions. We performed detailed plant water status measurements on a subset of lines having similar crop growth duration but contrasting genotypes at qtl12.1 under field (24 genotypes) and greenhouse (14 genotypes) conditions. The Way Rarem-derived allele of qtl12.1 was confirmed to improve grain yield under drought mainly through a slight improvement (7%) in plant water uptake under water-limited conditions. Such an apparently small increase in water uptake associated with this allele could explain the large effect on yield observed under field conditions. Our results suggest that this improvement of plant water uptake is likely associated with improved root architecture. [Copyright &y& Elsevier]

Abstract: In recent decades there has been steady reduction in the rate of increase in cereal yields worldwide. This paper aims to (1) characterise the changes in yield trends of spring (barley, oat and wheat) and winter cereals (rye and wheat) grown in Finland and (2) distinguish between plant breeding achievements and other potential contributors to changes in national yield trends and differences among crops. In this work we used long-term datasets from FAO (FAOSTAT, 2007) (1960–2005) and results from multi-location MTT Official Variety Trials (1970–2005). A mixed model technique was used to divide the yield trends in variety trials into two components: genetic improvements and environmental changes. All trends were characterised using 5 years moving averages. The study period was divided into three agronomically relevant sub-periods: (1) in 1960–1980 agriculture was mechanised and improved basic agricultural practices largely introduced, (2) in 1981–1994 intensified crop management practices were increasingly applied and (3) in 1995–2005 Finland had joined the European Union, which resulted in altered agricultural policies and markets. Plant breeding has successfully increased genetic yield potential of all cereal crops without any indication of reduced rates of improvement. Since 1995 the Finnish national yield trends declined for all crops except wheat, for which the trend levelled-off. The main reasons for this are: cereal production has become less intensive because of (1) application of an environmental programme aimed at increasing the sustainability of agriculture by reducing the environmental load it represents and (2) markedly decreased economic incentives to produce intensively as producer prices for cereals decreased and input prices remained unchanged. National yield trends did not decline because of lack of genetic improvement in yield potential. It is likely that future cereals yield trends will again respond to increasing demand for food, feed, biofuel production and global climate change. [Copyright &y& Elsevier]

Abstract: Many of the world''s rice-growing regions lack adequate irrigation facilities, and drought frequently reduces yield. This paper reviews drought-resistance traits in rice and their quantitative trait loci (QTLs), with emphasis on CT9993/IR62266, one of the most widely studied mapping populations, and suggests ways to develop cultivars that will perform well in drought-prone environments. Information about the type of drought faced in the target region – particularly the timing of the drought (late season terminal drought, early stage vegetative drought, and intermittent drought) and the intensity of the drought – are important in determining the specific plant traits required to improve drought resistance in rice. Most of these traits are related to drought avoidance strategy, so that the drought-resistant genotypes are able to maintain better internal water status, either by taking up more water through a better root system or by reducing the rate of plant water use. We identified and listed a number of QTLs for many drought-resistance traits, such as deep roots. We identified four key genomic regions on chromosomes 1, 4, 8, and 9 on which are co-located a number of QTLs for traits considered to be directly or indirectly responsible for grain yield under stress. These regions, once they have been more finely mapped, appear promising for eventual use in marker-assisted selection for development of drought-resistant rice varieties. In addition to selecting for specific traits or specific genomic regions, screening under managed drought conditions on the basis of yield itself or on spikelet fertility adjusted for flowering time appears useful, because of the relatively high degrees of heritability of these characters, for the development of drought-resistant rice cultivars, and it is currently practiced in some breeding programs. [Copyright &y& Elsevier]