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The soil acidity level is a key soil characteristic that determines soil nutrient availability, soil microbial activities and crop growth. However, studies on distribution and extent of soil acidity in Ethiopia are not available. This study was carried out to predict the extent and severity of soil acidity. The study used 88,265 soil pH samples collected from soil laboratories and 21,439 samples compiled from studies. Rainfall, altitude, slope gradient, soil, and land cover were considered to generate spatial autocorrelation and integrated into geospatial analysis to predict the soil pH. The performance of the kriging model was found to be satisfactory with a standard error of 0.77, RMSE of 0.51, and R2 of 0.74. The model estimates showed that 47% and 30.2% of the country’s total area and rainfed areas were acidic (pH

Salt stress is a globally increasing environmental detriment to crop growth and productivity. Exposure to salt stress evokes a complex medley of cellular signals, which rapidly reprogram transcriptional and metabolic networks to shape plant phenotype. To date, genetic engineering approaches were used with success to enhance salt tolerance; however, their performance is yet to be evaluated under realistic field conditions. Regulatory short non-coding RNAs (rsRNAs) are emerging as next-generation candidates for engineering salt tolerance in crops. In view of this, the present review provides a comprehensive analysis of a decade's worth of functional studies on non-coding RNAs involved in salt tolerance. Further, we have integrated this knowledge of rsRNA-mediated regulation with the current paradigm of salt tolerance to highlight two regulatory complexes (RCs) for regulating salt tolerance in plants. Finally, a knowledge-driven roadmap is proposed to judiciously utilize RC component(s) for enhancing salt tolerance in crops. This article is protected by copyright. All rights reserved.

Background Northeast China is one of the most important maize producing area in China. Due to temperature limitations on crop growth, whether this area can realize mechanical kernel harvesting maize (MKHM) variety will directly affect the stable development of maize in the region. The northern limits of early-maturing MKHM variety was analyzed under climate change in the study. Results The mean temperature during maize growth period increased at a rate of 0.22 °C/10a from 1960 to 2018. The average growth period for early-, middle- and late-maturing common harvest maize (CHM) variety was 123, 135 and 140 days, respectively, and the accumulated temperature above 10 °C (AAT10) was 2400 °C, 2800 °C, and 3100 °C. The early-maturing MKHM variety growth period was about 20 days longer than that of early-maturing CHM variety, and thus the AAT10 of MKHM variety was 2700 °C. During 2000-2018, the northern limits for the early-maturing CHM variety planting were located from south of Nenjiang and Wudalianchi (47°98' N-49°74' N), while the northern limits for the early-maturing MKHM variety was located in south Keshan, Nehe and Hailun (46°32' N-48°70' N), which was about 148 km southward compared to the northern limits of early-maturing CHM variety. Conclusion This study not only confirmed the northern limits of early-maturing MKHM variety, but also indicated that the development of MKHM variety offsets the influences of climate change on the northern limits of maize planting, which is very important for provide the sustainable development of maize in the region. This article is protected by copyright. All rights reserved.

Early vigour in wheat is a trait that has received attention for its benefits reducing evaporation from the soil surface early in the season. However, with the growth enhancement common to crops grown under elevated atmospheric CO concentrations (e[CO ]), there is a risk that too much early growth might deplete soil water and lead to more severe terminal drought stress in environments where production relies on stored soil water content. If this is the case, the incorporation of such a trait in wheat breeding programs might have unintended negative consequences in the future, especially in dry years. We used selected data from cultivars with proven expression of high and low early vigour from the Australian Grains Free Air CO Enrichment (AGFACE) facility, and complemented this analysis with simulation results from two crop growth models which differ in the modelling of leaf area development and crop water use. Grain yield responses to e[CO ] were lower in the high early vigour group compared to the low early vigour group, and although these differences were not significant, they were corroborated by simulation model results. However, the simulated lower response with high early vigour lines was not caused by an earlier or greater depletion of soil water under e[CO ] and the mechanisms responsible appear to be related to an earlier saturation of the radiation intercepted. Whether this is the case in the field needs to be further investigated. In addition, there was some evidence that the timing of the drought stress during crop growth influenced the effect of e[CO ] regardless of the early vigour trait. There is a need for FACE investigations of the value of traits for drought adaptation to be conducted under more severe drought conditions and variable timing of drought stress, a risky but necessary endeavour.

Applying Phosphorus (P) to global cropland supports crop growth and helps to address the increasing global food demand. However, poor management of P application leads to nutrient loss and environm...

Representing climate‐crop interactions is critical to Earth system modeling. Despite recent progress in modeling dynamic crop growth and irrigation in land surface models (LSMs), transitioning these models from field to regional scales is still challenging. This study applies the Noah‐MP LSM with dynamic crop‐growth and irrigation schemes to jointly simulate the crop yield and irrigation amount for corn and soybean in the central United States. The model performance of crop yield and irrigation amount are evaluated at county‐level against the USDA reports and USGS water withdrawal data, respectively. The bulk simulation (with uniform planting/harvesting management and no irrigation) produces significant biases in crop yield estimates for all planting regions, with root‐mean‐square‐errors (RMSEs) being 28.1% and 28.4% for corn and soybean, respectively. Without an irrigation scheme, the crop yields in the irrigated regions are reduced due to water stress with RMSEs of 48.7% and 20.5%. Applying a dynamic irrigation scheme effectively improves crop yields in irrigated regions and reduces RMSEs to 22.3% and 16.8%. In rainfed regions, the model overestimates crop yields. Applying spatially varied planting and harvesting dates at state‐level reduces crop yields and irrigation amount for both crops, especially in northern states. A “nitrogen‐stressed” simulation is conducted and found that the improvement of irrigation on crop yields is limited when the crops are under nitrogen stress. Several uncertainties in modeling crop growth are identified, including yield‐gap, planting date, rubisco capacity, and discrepancies between available data sets, pointing to future efforts to incorporating spatially varying crop parameters to better constrain crop growing seasons.

Changing irrigation water demand (IWD) and supply (IWS) patterns (size and time) under increased climate variability and socio-economic development is significantly effecting the water and food pro...

Agroecosystem models need to reliably simulate all biophysical processes that control crop growth, particularly the soil water fluxes and nutrient dynamics. As a result of the erosion history, truncated and colluvial soil profiles coexist in arable fields. The erosion‐affected field‐scale soil spatial heterogeneity may limit agroecosystem model predictions. The objective was to identify the variation in the importance of soil properties and soil profile modifications in agroecosystem models for both agronomic and environmental performance. Four lysimeters with different soil types were used that cover the range of soil variability in an erosion‐affected hummocky agricultural landscape. Twelve models were calibrated on crop phenological stages, and model performance was tested against observed grain yield, aboveground biomass, leaf area index, actual evapotranspiration, drainage, and soil water content. Despite considering identical input data, the predictive capability among models was highly diverse. Neither a single crop model nor the multi‐model mean was able to capture the observed differences between the four soil profiles in agronomic and environmental variables. The model's sensitivity to soil‐related parameters was apparently limited and dependent on model structure and parameterization. Information on phenology alone seemed insufficient to calibrate crop models. The results demonstrated model‐specific differences in the impact of soil variability and suggested that soil matters in predictive agroecosystem models. Soil processes need to receive greater attention in field‐scale agroecosystem modeling; high‐precision weighable lysimeters can provide valuable data for improving the description of soil–vegetation–atmosphere process in the tested models.

It is difficult for the handheld/backpack or ground machinery to spray pineapple plant fields because the plant profile is relatively inaccessible. In this situation, unmanned aerial vehicles (UAVs) are a good choice for easy access and no physical damage to the crops. Aerial spray quality and optimum application parameter settings can be influenced by many factors such as UAV type, UAV operating parameters, meteorological conditions, crop growth period, and pest species. The objective of this study was to investigate the effects of different meteorological conditions and UAV operating height on the spray application in pineapple fields. There were five treatments involving three UAV operating heights. Mylar cards, water-sensitive papers, and airborne concentrations of spray were sampled at various locations from -10 to 50 m downwind of the edge of the sprayed blocks. The results indicated that as the wind speed increased, the swath location was displaced 2 to 4 m, the percent area coverage uniformity changed along with the spray penetration capacity, and the 90% of total measured drift distance varied from 3.7 to 46.5 m. The test results again proved that droplet size and wind speed were significant factors in spray transport and impacted the UAV spray quality.

Photosynthesis in non-foliar organs plays an important role in crop growth and productivity, and it has received considerable research attention in recent years. However, compared with the capability of photosynthetic CO2 fixation in leaves, the distinct attributes of photosynthesis in the non-foliar organs of wheat (a C3 species) are unclear. This review presents a comprehensive examination of the photosynthetic characteristics of non-foliar organs in wheat. Compared with leaves, non-foliar organs had a higher capacity to refix respired CO2 , higher tolerance to environmental stresses and slower terminal senescence after anthesis. Additionally, whether C4 photosynthetic metabolism exists in the non-foliar organs of wheat is discussed, as is the advantage of photosynthesis in non-foliar organs during times of abiotic stress. Introducing the photosynthesis-related genes of C4 plants into wheat, which are specifically expressed in non-foliar organs, can be a promising approach for improving wheat productivity.

Soil sensors and plant wearables play a critical role in smart and precision agriculture via monitoring real-time physical and chemical signals in the soil, such as temperature, moisture, pH, and pollutants and providing key information to optimize crop growth circumstances, fight against biotic and abiotic stresses, and enhance crop yields. Herein, the recent advances of the important soil sensors in agricultural applications, including temperature sensors, moisture sensors, organic matter compounds sensors, pH sensors, insect/pest sensors, and soil pollutant sensors are reviewed. Major sensing technologies, designs, performance, and pros and cons of each sensor category are highlighted. Emerging technologies such as plant wearables and wireless sensor networks are also discussed in terms of their applications in precision agriculture. The research directions and challenges of soil sensors and intelligent agriculture are finally presented.

Abiotic stress is one of the main threats affecting crop growth and production. An understanding of the molecular mechanisms that underpin plant responses against environmental insults will be crucial to help guide the rational design of crop plants to counter these challenges. A key feature during abiotic stress is the production of nitric oxide (NO), an important concentration dependent, redox-related signalling molecule. NO can directly or indirectly interact with a wide range of targets leading to the modulation of protein function and the reprogramming of gene expression. The transfer of NO bioactivity can occur through a variety of potential mechanisms but chief among these is S-nitrosylation, a prototypic, redox-based, post-translational modification. However, little is known about this pivotal molecular amendment in the regulation of abiotic stress signalling. Here, we describe the emerging knowledge concerning the function of NO and S-nitrosylation during plant responses to abiotic stress.

Weed presence early in the life cycle of maize (typically, from emergence through the 8 to 12 leaf growth stage) can reduce crop growth and yield and is known as the critical weed‐free period (CWFP). Even if weeds are removed during or just after the CWFP, crop growth and yield often are not recoverable. We compared transcriptome responses of field‐grown hybrid maize at V8 in two consecutive years among plants grown under weed‐free and two weed‐stressed conditions (weeds removed at V4 or present through V8) using RNAseq analysis techniques. Compared with weed‐free plant responses, physiological differences at V8 were identified in all weed‐stressed plants and were most often associated with altered photosynthetic processes, hormone signaling, nitrogen use and transport, and biotic stress responses. Even when weeds were removed at V4 and tissues sampled at V8, carbon: nitrogen supply imbalance, salicylic acid signals, and growth responses differed between the weed‐stressed and weed‐free plants. These underlying processes and a small number of developmentally important genes are potential targets for decreasing the maize response to weed pressure. Expression differences of several novel, long noncoding RNAs resulting from exposure of maize to weeds during the CWFP were also observed and could open new avenues for investigation into the function of these transcription units.

To meet future world food and fiber demands, plant breeders must increase the rate of genetic improvement of important agricultural crops. One of the biggest obstacles now facing crop scientists is a phenotyping bottleneck. To ease this burden, the emerging technology of unmanned aerial systems (UAS) presents an exciting opportunity. To assess the utility of UAS, it is important to investigate their application across multiple crop species. Terminal plant height is of great importance to maize (Zea mays L.) and sorghum [Sorghum bicolor (L.) Moench] breeders and has been hypothesized to be useful but has been logistically impractical to measure in the field. In this study, we statistically analyzed in depth the ability of UAS to estimate height in sorghum (advanced and early generation material) and maize (optimal and late material) and the application of these estimates in breeding programs. We found that UAS explain genotypic variation similarly to ground-truth methods and that the repeatability of the methodology is high (R = 0.61–0.99), indicating effective differentiation of genotypes. Additionally, correlations between ground truth and UAS measurements were moderate to high for all materials (r = 0.4–0.9). Finally, we present a novel application for the technology in the form of high-resolution temporal growth curves. Using these UAS-generated growth curves, new physiological insights can be obtained and new avenues of scientific investigation are possible.

The objective of this study is to increase our understanding of the heritability of starch quality characteristics, and of their sensitivity to effects of the growing environment. To this end, variability of pasting, thermal and gel properties of starch was examined using grains of five varieties of wheat (Triticum aestivum L.), grown in commercial cropping systems in five locations in Australia in 2 years. About 60–70% of the variability of DSC thermal properties and hardness of starch gels kept at 4°C for 24 h was contributed by factors related to growing conditions. Starch pasting properties had a higher degree of heritability (30–35%), although environmental conditions also contributed significantly to variability. A key effect of the growing environment appeared to be on the stability of the crystallites in the starch granules. While the results obtained are characteristic of the varieties used in this study, and of the specific environmental factors that influenced crop growth, the results nevertheless indicate that atmospheric and soil conditions can affect functional properties of starch that are important in foods and other applications. The finding that pre-anthesis conditions seem to affect the structure of starch raises interesting questions about the mechanism of starch biosynthesis in wheat grains.

Chickpea (Cicer arietinum L.) roots exude carboxylates. While chickpea commonly grows where the topsoil dries out during crop growth, the importance of carboxylate exudation by the roots and mobilization of soil P from below the dry topsoil has not been examined. The study investigates the response of carboxylate exudation and soil P mobilization by this crop to subsoil P fertilizer rate. In constructed soil columns in the glasshouse, the P levels (high, low, and nil P) were varied in the well-watered subsoil (10-30 cm), while a low level of P in the dry topsoil (0-10 cm) was maintained. At flowering, rhizosphere carboxylates and rhizosphere soil from topsoil and subsoil roots were collected separately and analyzed. The concentration of total carboxylates per unit rhizosphere mass in the subsoil was nearly double that of the topsoil. Plants depleted sparingly soluble inorganic P (Pi), NaOH-Pi, and HCl-Pi, along with the labile Pi (water soluble and NaHCO3-Pi). The P depletion by plants was greater from the subsoil than the topsoil. The study concluded that depletion of sparingly soluble P from the chickpea rhizosphere in the subsoil was linked with the greater levels of carboxylates in the rhizosphere. These findings indicate that chickpea, with its deep rooting pattern, can increase its access to subsoil P when the topsoil dries out during crop growth by subsoil rhizosphere modification.

The absence of recent data regarding the nutritional needs of modern soybean [ Glycine max (L.) Merr.] production systems necessitates a greater comprehensive understanding of nutrient uptake, partitioning, and remobilization. The objective of this study was to evaluate macro- and micronutrient accumulation and partitioning in current soybean cultivars. Across 3 site-years, plants were sampled at seven growth stages and divided into four plant tissue fractions for quantification of nutrient uptake. Accumulation (per ha) of 275 kg N, 21 kg P (48 kg P 2 O 5 ), 172 kg K (207 kg K 2 O), 113 kg Ca, 50 kg Mg, 19 kg S, 335 g Zn, 371 g Mn, 325 g B, 849 g Fe, and 63 g Cu were required to produce approximately 3500 and 9500 kg ha –1 of grain and total biomass, respectively. Supplemental fertility modestly increased biomass and yield (2%), but did not alter nutrient partitioning or harvest index. Nutrients with high harvest index (i.e., percentage of total nutrient accumulation partitioned to grain) values included P (81%), N (73%), Cu (62%), and S (61%), which may serve as a limitation to high yield. Seasonal patterns of nutrient accumulation suggested that K and Fe were acquired primarily during late vegetative growth while the uptake of N, P, Ca, Mg, S, Zn, Mn, B, and Cu were more equally distributed between vegetative and seed-filling growth phases. These results document the rate and duration of macro- and micronutrient accumulation in soybean, and highlight the importance of adequate nutrient availability during key crop growth periods.

Crop growth is related to radiation-use efficiency (RUE), which is influenced by the nitrogen (N) status of the crop, expressed at canopy level as specific leaf N (SLN) or at plant level as N nutrition index (NNI). To determine the mechanisms through which N affects dry-matter (DM) production of forage kale, results from two experiments (N treatment range 0–500 kg ha−1) were analysed for fractional radiation interception (RI), accumulated radiation (Racc), RUE, N uptake, critical N concentration (Nc), NNI and SLN. The measured variables (DM, RI and SLN) and the calculated variables (NNI, Racc and RUE) increased with N supply. RUE increased from 0·74 and 0·89 g MJ−1 IPAR for the control treatments to 1·50 and 1·95 g MJ−1 IPAR under adequate N and water in both experiments. This represented an increase in RUE of 52–146% for the range of N treatments used in both experiments, whilst Racc increased by 9–17%, compared with the control treatments. Subsequently, the total DM yield of kale increased from 6·7 and 8 t DM ha−1 for the control treatments to ≥ 19 t DM ha−1 when ≥150 kg N ha−1 was applied. The DM yields for the 500 kg N ha−1 treatments were 25·5 and 27·6 t DM ha−1 for the two experiments. RUE increased linearly with SLN, at an average rate of 0·38 g DM MJ−1 IPAR per each additional 1 g N m−2 leaf until a maximum RUE of 1·90 g MJ−1 IPAR was reached in both experiments. There were no changes in RUE with SLN of > 2·6 g m−2 and NNI >1, implying luxury N uptake. RUE was the most dominant driver of forage kale DM yield increases in response to SLN and NNI.

Crop growth responses to rising atmospheric carbon dioxide (CO) concentrations and potential rising air temperatures can be a challenge for the scientist to convey in a form that the public can understand. Outputs of most modeling studies and meta-analyses of crop responses to these two important variables can be complicated and difficult to comprehend. This paper merges two mathematical formulations, clearly illustrated in two-dimensional graphics, to create a direct representation of crop growth responses to a range of both CO concentrations and air temperatures. The output is a direct graphical view of crop growth responses to both CO and temperature in three dimensions. The three-dimensional graphic can be rotated to illustrate representative growth responses from various perspectives.

Due to their outstanding properties, interest in lasers has increased greatly in precision agriculture as a potential tool for non-chemical weed control. unwanted plants have a negative effect on crop growth, especially in close surroundings. Weed control based on mechanical (e.g. hoeing) or thermal (flaming) methods do not meet the precision requirements to preserve crop plants. An innovative combination of image processing and laser technology is promising.

The objectives of this study were to determine the proportion of indigestible neutral detergent fibre (iNDF) in the neutral detergent fibre (NDF) fraction of sugarcane, to estimate changes in NDF digestibility (NDFD) during the harvesting window and to predict sugarcane digestibility based on its fibre fractions. Whole plants of the IAC86-2480 and IAC93-3046 varieties were collected during the harvesting windows in 2007 and 2009, respectively. The in vitro true dry matter digestibility (IVTDMD) and fibre contents (NDF, iNDF, acid detergent fibre) were determined by near infrared reflectance spectroscopy (NIRS). The NDFD and potentially digestible NDF digestibility (pdNDFD) were estimated, and the fractional digestion rate of pdNDF was calculated. There was no relationship between growing days and iNDF as a proportion of NDF (P = 0·28) or with the fractional digestion rate of pdNDF (P = 0·30). Therefore, NDFD (mean = 335 g kg−1) and pdNDFD (mean = 657 g kg−1) remained almost constant during the harvesting window (P = 0·70 and P = 0·32 respectively). Acid detergent fibre and NDF were the best predictors of sugarcane dry matter (DM) digestibility. In conclusion, NDFD seems to be unchanged during crop growth. The point at which to harvest sugarcane as a forage source should therefore be decided based on NDF concentration, which is greatly influenced by sucrose accumulation.

The assessment of biophysical crop suitability requires datasets on soil and climate. In this study, we investigated the differences in topsoil properties for the dominant soil mapping units between two global soil datasets. We compared the ISRIC World Soil Information Center’s World Inventory of Soil Emissions Potential 5 by 5 arc min Soil Map of the World (ISRIC-WISE 5by5 SMW ) with the Harmonized World Soil Database (HWSD) in 0.5 arc min. We also incorporated annual mean temperature and mean precipitation from two global climate datasets that were the WorldClim measurement-based climate dataset and the Kiel Climate Model (KCM) modelled results of global climate from 1960 to 1990. We then applied a fuzzy logic approach using different combinations and resolutions of the datasets to determine the effects on the extent and distribution of suitable areas for 15 crops. We only used the spatially dominant soil class in the mapping units in the soil databases (resampled to the same resolution of 5 arc min), and we found that the estimates of topsoil properties (0–20 cm in ISRIC-WISE and 0–30 cm in HWSD) of the seven analysed parameters were up to 40% lower in most of the HWSD than in the ISRIC-WISE 5by5 SMW. Results from the KCM are 0.1 °C (1%) lower in mean global annual temperature and 20% higher in average global annual precipitation compared with the WorldClim data. The HWSD-based runs resulted in 10% less crop-suitable land than the ISRIC-WISE 5by5 SMW-based results. The KCM simulations predicted 1% less crop-suitable land than the WorldClim model. Despite generalizations, our results demonstrate that discrepancies in crop suitable areas are largely due to the differences in the soil databases rather than to climate.

Crop tolerance and weed control in winter wheat were investigated to evaluate the influence of post-emergence weed harrowing at different crop growth stages on selectivity, crop recovery and crop yield. The importance of growth stage was investigated in autumn (Denmark) and spring (Germany). Selectivity was chosen as a measure of the relationship between weed control and crop soil cover, with crop recovery as a measure of how crop yield was affected by soil cover in the absence of weeds. Selectivity was unaffected by crop growth stage in autumn and spring. In autumn, 80% weed control was associated with 6% crop soil cover, whereas in spring, 80% weed control corresponded to 26% crop soil cover. Crop recovery was higher in late growth stages in autumn and spring. With 25% crop soil cover, crop yield losses occurred in the ranges of 1–4% in autumn and 0.3–0.8% in spring. Weed control experiments revealed that the maximum crop yield response to harrowing was comparable with herbicide treatment. The average yield gain was 13% in autumn (Denmark) and 27% in spring (Germany). This study contributes parameter estimates that can be used in future models to evaluate optimum harrowing intensity.

The gradual disruption of the ozone layer in the stratosphere has resulted in increased exposure of plants to ultraviolet-B (UV-B, 280-315 nm) radiation. UV-B radiation is known to affect crop growth and quality negatively. A study was conducted to determine the impact of elevated UV-B radiation levels on the isoflavones and phenolic compound concentrations of seven soybean varieties. UV-B radiation significantly reduced the concentration of most isoflavones and phenolic compounds in soybean seeds. Exposure to elevated UV-B levels overall resulted in 35 % reduction in total isoflavones and 31 % in phenolic compounds concentrations. The effect on individual isoflavones and phenolic compounds depended on the compound and variety, but UV-B overwhelmingly reduced concentrations. This study suggests that increased UV-B radiation negatively impacted soybean quality by reducing the concentration of compounds that have health-beneficial properties.

The soybean cyst nematode (Heterodera glycines Ichinohe) is the main yield limiting pathogen of soybean [Glycine max (L.) Merr.] in the USA. Resistant cultivars are the most efficient management tool today. Our research studied the physiological basis of yield differences between H. glycines-susceptible and H. glycines- resistant cultivars developed from the Hartwig, PI 88788, and Peking sources of resistance at two locations in Iowa during 2005 and 2006. Supplementing resistance with chemical control may improve soybean yield and/or nematode control, so nematicide application {aldicarb[2-methyl-2 (methylthio) propionaldehyde O-(methylcarbamoyl) oxime]} was included as an experimental factor. Aldicarb increased total plant biomass by 9% during R1-R5 soybean growth stages, but there was no increase in seed yield. Yields of the resistant cultivars were greater than those of the susceptible cultivars, except for the Peking source. Compared with the susceptible cultivars, cultivars with H. glycines resistance from PI 88788 had a 13% increase in yield associated with a 15% increase in growth during R1-R5. In cultivars with resistance from Hartwig, a 6% increase in yield was associated with a 4% increase in R1-R5 duration and increased seed-set efficiency. This work demonstrates that yield increases due to resistance to H. glycines can be attained by different physiological mechanisms associated with the different resistance sources and probably are controlled by different genes. This opens the possibility of pyramiding genes conferring resistance by different mechanisms. © Crop Science Society of America. Fil: Rotundo, José Luis. University of Iowa; Estados Unidos. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Instituto de Investigaciones Fisiológicas y Ecológicas Vinculadas a la Agricultura. Universidad de Buenos Aires. Facultad de Agronomía. Instituto de Investigaciones Fisiológicas y Ecológicas Vinculadas a la Agricultura; Argentina Fil: Tylka, G.L.. Syngenta Crop Protection; Estados Unidos Fil: Pedersen, P.. University of Iowa; Estados Unidos

Drought is common to Iran and the agricultural sector is its main victim. Reducing demand for irrigation water is considered the best management practice to alleviate losses. An equitable water reduction approach has been traditionally applied in the management of irrigation systems. This research work examines and compares this approach with that based on the optimization method to manage agricultural water demand during drought to minimize damage. To evaluate these methodologies, the 1999 drought in the Zayandeh Rud irrigation system was selected and the required models developed. In the optimization method, crop growth stages and their sensitivity to water stress at different stages are embedded in the calculations. The results show that the optimization method resulted in 42% more income for the agricultural sector using the same amount of water allocated in the 1999 drought. This difference emphasizes the importance of water allocation with respect to growth stages rather than simply cutting allocations on an equitable basis to combat water scarcity. However, managing the system using the optimization method is more complex and requires a new framework and planning to make it operational. Copyright © 2009 John Wiley & Sons, Ltd. La secheresse est commune en Iran et le secteur agricole en est la principale victime. La reduction de la demande en eau d'irrigation est consideree comme la meilleure pratique de gestion pour attenuer les pertes. Une approche equitable des reductions d'allocation en eau a ete traditionnellement appliquee a la gestion des systemes d'irrigation. Ce travail de recherche examine et compare cette approche avec celle qui est fondee sur une methode d'optimisation minimisant les dommages dans la gestion de la demande en eau agricole au cours de la secheresse. Pour evaluer ces methodes, la secheresse de 1999 dans le systeme d'irrigation Zayandeh Rud a ete selectionnee et les modeles ont ete developpes. La methode d'optimisation integre dans les calculs les stades de croissance des cultures et leur sensibilite au stress hydrique. Les resultats montrent que l'optimisation conduit, pour la secheresse de 1999, a un supplement de revenu agricole de 42% en utilisant la meme quantite d'eau. Cette difference montre l'importance de l'allocation de l'eau en fonction des stades de croissance plutot que de simplement couper l'eau sur une base equitable pour lutter contre la penurie d'eau. Toutefois, la gestion d'un systeme optimise est plus complexe et exige un nouveau cadre de planification pour le rendre operationnel. Copyright © 2009 John Wiley & Sons, Ltd.

Yield failure is often caused by the uncertainty of supply or the shortage of water at the critical period of crop growth. This situation compels farmers and engineers to find ways to efficiently use the available resource. Reduction of irrigation depth or extension of irrigation interval are the methods commonly adopted. Another alternative is the application of the rotational irrigation technique instead of continuous irrigation. The question is how to adjust the water supply to minimize crop yield losses. Water supply itself is a dynamic parameter depending on farm size, canal capacity and crop growth stages. The distribution factor (DF) is a technique of water distribution based on the dynamic character of the supply over the growth stages. It allows categorization of the allocation of the available water in the farm within the limit of the channel capacity to satisfy crop water needs. The procedure was applied to a set of 24 farms in 2006 in the Chianan Irrigation Association which frequently experiences water shortages. The results showed that if a uniform reduction of water supply could be applied during moderate water shortages, DF made it possible to rationally distribute water among rotational groups in severe shortage conditions. Copyright © 2008 John Wiley & Sons, Ltd. L'echec de rendement est souvent cause par l'incertitude de l'approvisionnement ou la penurie d'eau a la periode critique de croissance des cultures. Ceci oblige agriculteurs et ingenieurs a trouver des moyens efficaces d'utiliser la ressource disponible. La reduction de la dose d'irrigation ou la prolongation de l'intervalle d'irrigation est la methode couramment adoptee. Une autre alternative est l'application de la technique de rotation au lieu de l'irrigation continue. La question est de savoir comment ajuster l'approvisionnement en eau pour reduire les pertes de rendement. L'approvisionnement est un parametre dynamique, fonction de la taille de l'exploitation, la capacite du canal et la phase de croissance des cultures. Le facteur de distribution (DF) est une technique de distribution d'eau fondee sur le caractere dynamique de l'offre. Il permet de repartir l'eau disponible dans la limite de la capacite du canal pour satisfaire les besoins des cultures. La procedure a ete appliquee a un ensemble de 24 exploitations en 2006 Chianan Irrigation Association, qui connait souvent des penuries d'eau. Les resultats ont montre que si la reduction uniforme d'eau pourrait etre appliquee en cas de penurie moderee, DF a permis de distribuer rationnellement l'eau entre les groupes de rotation dans les conditions de grave penurie. Copyright © 2008 John Wiley & Sons, Ltd.

This article has applied the results of plant growth experimentation under various conditions, including high carbon dioxide concentrations; low light, water, and nutrient levels; and the effect of low pressure and magnetic fields to plant growth and, more specifically, crop productivity. By examining the outcomes of these experiments the feasibility of crop growth under conditions that would be expected on Mars can be demonstrated. It is shown that stress factors likely to be encountered on Mars, including low light water and nutrient levels, can be compensated for through the use of an enriched CO 2 environment. Other environmental factors are shown to be either not limiting on crop productivity, or easily compensated for in a managed greenhouse.

An early prediction of crop biomass at maturity and yield is important in different circumstances. The use of spectral reflectance indices, such as the Normalized Difference Vegetation Index (NDVI), has been proposed as a fast, nondestructive way of estimating crop growth capacity. In this study, we examined whether NDVI assessment relatively early in the crop cycle may be useful for predicting final biomass and yield in wheat. To that end, NDVI was measured and biomass quantified regularly from tillering to maturity for six different wheat genotypes grown under a contrasting range of N and water availabilities. In addition, final biomass and yield were measured at maturity. In line with expectations from the literature, we found that NDVI at milk-grain stage was well correlated to final yield and biomass. However, it was also observed that NDVI at the onset of stem elongation was also reasonably correlated to both attributes. Because crop growth in wheat from the end of tillering to anthesis is related to the determination of grain number and yield, we propose the use of NDVI at the onset of stem elongation as a complementary criterion for establishing the required late crop management (N fertilisation, irrigation) practices.

Determining MZ (management zone)-specific optimal N rate is a challenge in precision crop management. The objective of this study was to evaluate the potential of applying a crop growth model to simulate corn (Zea mays L.) yield at various N levels in different MZs and estimate optimal N rates based on long-term weather conditions. Three years of corn yield data were used to calibrate a modified version of the CERES-Maize (Version 3.5) model for a commercial field previously divided into four MZs in eastern Illinois. The model performance in simulating corn yield for two hybrids (33G26 and 33J24) at five N levels in two independent years was evaluated. Economically optimum N rates (EONRs) were estimated based on 15 yr of simulation (1989-2003). The model explained approximately 59 and 93% of yield variability during calibration and validation, respectively. The model performed well at non-zero N rates, with most of the simulation errors being

The agroecosystem models THESEUS and OPUS were tested with data obtained from three agricultural experimental field plots on sandy soils without groundwater located at the moraine landscape in East Brandenburg, Germany. At each of these plots, a separate agricultural management practice was applied. Measurements of soil water contents, pressure heads, above-ground crop biomass, and crop yield from these three plots were compared with the corresponding simulation results of both models. The comparisons of simulated with measured outputs were analyzed using the modeling-efficiency index IA. According to these analyses, both models simulated adequately the time courses of volumetric soil water contents and above-ground crop biomass, but the time courses of pressure heads were predicted with a lower quality by both models. As for the pressure heads, the yields simulated with both models showed greater discrepancies in comparison with the observed ones. This indicates the need of a site-specific parameter calibration of the crop-growth modules, especially for that included in OPUS. Simulation des Bodenwasserhaushaltes und des Pflanzenwachstums mit den Modellen THESEUS und OPUS Die Modelle THESEUS und OPUS wurden mit Messdaten von drei Versuchsfeldern getestet. Diese Versuchsfelder liegen in der Moranenlandschaft Nordostdeutschlands auf sandigen Boden ohne Grundwasseranschluss. Auf diesen drei Versuchsfeldern wurden jeweils unterschiedliche Anbaustrategien fur eine Fruchtfolge angewendet. Die Ergebnisse der Messungen von Bodenwassergehalten, Tensionen, oberirdischer Biomasse und Ertrag wurden mit den entsprechenden Resultaten der beiden Modelle verglichen. Diese Vergleiche wurden mit Hilfe des Ubereinstimmungsindexes IA analysiert. Diese Analyse ergab, dass beide Modelle die Dynamik der Bodenwassergehalte und der oberirdischen Biomasse gut und die der Tensionen nur eingeschrankt nachvollziehen konnen. Grosere Abweichungen ergaben sich auch zwischen den gemessenen und den von beiden Modellen simulierten Ertragen. Dies weist darauf hin, dass fur prazise Ertragsbestimmungen die Pflanzenwachstumsmodule beider Modelle, insbesondere aber das Modul von OPUS, standortspezifisch uberpruft und gegebenenfalls kalibriert werden mussen.

Varying atmospheric nitrogen (N) depositions for different crops were observed at Bad Lauchstadt (Saxony-Anhalt, Germany) when using the ITNI system (ITNI = Integrated Total Nitrogen Input), which is based on the 15N isotope dilution method. These differences were only partly explained by climatic influences. The effects of crops on the atmospheric N deposition measured by the ITNI system are discussed. For this purpose, data of six different plant species recorded in 1998 were re-analyzed. It was found that the airborne N input is closely correlated with the morphology and metabolism of crops. Daily atmospheric N depositions of 129.0–360.8 g per hectare were measured for the plant species used. The nutritional supply of plants, especially with N, is another factor of influence on the N input from the atmosphere which should be considered. To investigate this aspect, a pot experiment was conducted with the grass Lolium perenne at three different N levels. An increase in the airborne N uptake (corresponding to N fertilization) was observed as biomass production rose. Einfluss von Nutzpflanzenarten und deren Wachstum auf die atmospharische Stickstoffdeposition Im Rahmen von atmogenen Stickstoffdepositionsmessungen am Standort Bad Lauchstadt (Sachsen-Anhalt, Deutschland) mittels des auf der 15N-Verdunnungsmethode beruhenden ITNI-Systems (ITNI = Integrated Total Nitrogen Input), konnte festgestellt werden, dass es in Abhangigkeit von der Nutzpflanzenart zu verschiedenen N-Depositionen kommt. Diese Unterschiede liesen sich nur teilweise durch klimatische Einflusse erklaren. Im Beitrag wird die Wirkung der Pflanzenart auf den atmospharischen N-Eintrag diskutiert. Dazu wurden Datensatze des Jahres 1998, in dem sechs Nutzpflanzenarten getestet wurden, herangezogen. Es zeigte sich, dass die atmogene N-Deposition sehr stark von der Pflanzenart bzw. deren Stoffwechsel und morphologischen Merkmalen abhangig ist. Fur die untersuchten Nutzpflanzen konnten tagliche atmospharische N-Eintrage in der Grosenordnung von 129 bis 360,8 g pro Hektar festgestellt werden. Da diesbezuglich auch die Nahrstoffversorgung von Pflanzen insbesondere mit N eine Rolle spielt, wurde ein Gefasexperiment angelegt, in dem der Einfluss des Grases Lolium perenne auf den atmogenen N-Input bei drei N-Dungungsstufen untersucht wurde. Mit steigender Biomassebildung, entsprechend der N-Dungung, kam es zu einer Zunahme des atmogenen N-Eintrages.

Summary Most herbicide applications to sugar beet (Beta vulgaris L.) are made to the whole crop area, but there is the opportunity to restrict applications to the crop row, decreasing the usage of herbicide by up to 70%. However, this would require greater use of mechanical weed control between rows. Experiments were performed in two seasons to evaluate the weed control performance of a novel, vision-guided, inter-row hoe in sugar beet crops grown on a peat fen soil. Hoe lateral placement was within ±30 mm. A precise hoeing and band spraying treatment was compared with overall herbicide use, and with treatments in which the herbicide applications were replaced by hand weeding to minimize competition between crop and weeds. Two hoe passes were made in each season, at crop growth stages of two and 10–12 true leaves in the first season and four and eight true leaves in the second season. Plant population density was not affected by treatment, indicating that none of the treatments caused crop plant loss. Use of the guided hoe controlled weeds better than overall spraying. Crop yields were not significantly different between treatments, indicating that weed control prevented competition with the crop in all treatments.

Many soil physical properties and crop yield are affected by compaction. The effects of compaction of two axle loads resulting from wheel traffic on soil bulk density and crop growth were investigated. Subsoiling as a method to alleviate or reduce effects of soil compaction was evaluated. As a result of compacting loads in 2000, corn (Zea mays L.) yield was reduced by 26.8 and 14.5% in 2000 and 2001. Even two years after compaction, soil bulk density was 1.6 to 6.1% greater than the zero-load from 10- to 50-cm depths by 8- and 19-Mg axle loads. Plants in compacted plots had a greater concentration of roots near the base of the plant compared with the plants in the zero-load plots. Plants in the subsoiled plots had fewer roots concentrated near the base of the plant compared with the plants in the nonsubsoiled plots for each load. Plant height was also significantly reduced by compaction. Compaction affected plant and soil properties, but subsoiling removed the compaction effect and improved soil properties, growth, and yield.

Tuber dormancy enables yams to survive in the ground during the dry season and post-harvest storage. Three clones of Dioscorea rotundata were harvested after five intervals and then stored in a cooler (20.6°C) or at ambient temperature (27.8°C). The time from harvest to sprouting was shorter as harvest was delayed. The period from sowing to sprouting for each clone was similar for tubers harvested from 140 days after planting, but tubers harvested earlier took longer to sprout. The cooler temperature delayed sprouting. Tubers of two clones sprouted after only 70 days of crop growth. If the dormancy period of these young tubers can be broken, the generation time of yam crop improvement programmes could be considerably reduced.

Leaf nitrogen content and light intensity affect leaf photosynthesis. Responses of cotton (Gossypium hirsutum L.) leaf photosynthesis to nitrogen and light were developed and used in a framework that scales from leaf photosynthesis to canopy radiation use efficiency (RUE). This was then used to explore the impact of nitrogen and light dynamics on RUE of cotton canopies. Photosynthetic rate and nitrogen concentration of leaves (specific leaf nitrogen, SLN) were measured from two field experiments in which the rate of nitrogen application was varied. The overall shape of the relationship between photosynthesis and SLN of individual leaves was consistent with that for other species, being described by an exponential rise to a maximum of 32.49 ± 1.08 μmol CO 2 m -2 s -1 . Incorporating the influence of age improved the relationship, showing an impact of leaf age independent of SLN. The photosynthesis relationship developed should be appropriate for use in simulating cotton crops. The approach used to scale from leaf photosynthesis to canopy RUE was effective in capturing the variation in the RUE of cotton as observed in three field experiments. There appeared to be little impact of the ontogenetic changes in light extinction coefficient and vertical gradients of SLN within the canopy on the variation in RUE. For crop simulation purposes, this simplifies the process of modulating RUE in growth models.

An ongoing programme of archaeological aerial reconnaissance in southwestern Transylvania, the first time such a programme has been conducted in Romania, revealed quite large numbers of negative cropmarks or parchmarks, particularly in the dry summer of 2000. These areas of restricted crop growth indicated the presence of buried stone-walled buildings, predominantly of Roman date, which were previously unknown. Important discoveries included much of the internal plan of the auxiliary fort at Cigmau; an extensive civil settlement to the east of that fort; buildings within the civil settlements outside the forts at Vetel (Micia) and Razboieni; buildings and property boundaries within the municipium at Apulum (Alba Iulia); and villas at Oarda and Vintu de Jos. By contrast, positive cropmarks, enhanced growth reflecting the existence of buried pits or enclosure ditches, were observed only rarely. Explanations for this phenomenon linked to a bias in the reconnaissance programme or to a general absence of enclosed sites within the archaeological record in the area are rejected. The preferred explanation relates to local soil conditions, whereby the widespread, deep alluvial soils reduce the contrast in moisture content between buried archaeological ditches or pits and the surrounding soil matrix so that positive cropmarks are rarely formed. Copyright © 2003 John Wiley & Sons, Ltd.

The effect of plant growth on the mineralization of organic matter and distribution of soil S fractions (plant available SO42—, adsorbed SO42—, carbon-bonded S, ester-bonded S, and residual-S) in the rhizosphere was studied in a greenhouse experiment using a rhizobag technique. In this study wheat, oilseed rape and radish were grown on two soils, a Haplic Acrisol and a Hortic Anthrosol. Significant differences between S fractions in the rhizosphere and non-rhizosphere were determined in dependence on soil type and crop species. In all cropped treatments lower amounts of ester-bonded S and higher levels of residual-S were found in the rhizosphere than in the non-rhizosphere, while the amount of carbon-bonded S fractions was similar. These results indicate firstly, that the arylsulfatase activity was higher in the rhizosphere than in the non-rhizosphere and secondly, that mass flow of SO42—-S to the rhizosphere increased after mineralization of residual-S. Compared to the non-vegetated soil, the ester-bonded S fraction of wheat and oilseed rape decreased in the rhizosphere revealing that the mineralization of organic S in the rhizosphere is related to the crop type. Einfluss des Pflanzenwachstums auf die Verteilung und Mineralisierung von Schwefelfraktionen in der Rhizosphare Der Einfluss des Pflanzenwachstums auf die Mineralisierung organischer Substanz und die Verteilung verschiedener Schwefel-fraktionen (pflanzenverfugbarer S, adsorbierter S, C-gebundener S, Ester-gebundener S und Residual-S) in der Rhizosphare und im nicht durchwurzelten Boden wurde in einem Gewachshausversuch untersucht, wobei eine ,Wurzelbeuteltechnik‘ angewandt wurde. Im Rahmen der vorliegenden Studie wurden Weizen, Raps und Rettich auf zwei Boden, einem Haplic Acrisol und einem Hortic Anthrosol kultiviert. Signifikante Unterschiede bestanden zwischen den Gehalten der einzelnen Schwefelfraktionen in der Rhizosphare und im nicht durchwurzelten Raum in Abhangigkeit vom Bodentyp und der Kulturart. Bei Pflanzenbewuchs waren im durchwurzelten Raum stets niedrigere Gehalte an Ester-gebundenem und hohere Gehalte an Residual-S zu finden als im nicht durchwurzelten Bodenbereich. Im Vergleich hierzu veranderten sich die Gehalte an C-gebundenem Schwefel nicht. Dies deutet darauf hin, dass die Arylsulfatase-Aktivitat in der Rhizosphare hoher war als im nicht durchwurzelten Boden. Des weiteren scheint die Mineralisation von Residual gebundenem Schwefel zu einem erhohten Massenfluss von Sulfat in den durchwurzelten Raum gefuhrt zu haben. Die Ester-gebundenen Schwefelgehalte lagen in der Rhizosphare von Weizen und Raps signifikant niedriger als im unbewachsenen Boden, wodurch kulturartspezifische Einflusse auf die Mineralisation organisch gebundenen Schwefels deutlich werden.

The optimum sowing dates for soybean cv. Gaurav were derived for Jabalpur, Raipur and Gwalior in the state of Madhya Pradesh in central India. Dates were derived based on two strategies: (a) probabilities of rainfall and temperature events using ClimProb, a PC based software package, and (b) the CROPGRO Soybean v3.0 crop growth simulation model. In Madhya Pradesh, the optimum sowing dates for multiple cropping, with the first crop as soybean under rainfed conditions, are between weeks 25 and 27, while the optimum sowing dates for rainfed mono-cropping are between weeks 28 and 29.

This paper presents a prediction system for regional crop growth in Sweden, recently set up at SMHI (Swedish Meteorological and Hydrological Institute). The system includes a state-of-the-art crop growth model, WOFOST (WOrld FOod STudies) and inputs from meteorological mesoscale analysis. The simulated crops are spring barley, spring rape, oats and winter wheat, and the period of investigation is 1985–98. The simulated water-limited grain yield is used as a predictor in the yield prediction procedure. The technological time trend describing the yearly increase of the production level is accounted for as well. Yield prediction based on crop growth modelling is justified since the ability to forecast the yield is higher compared to that using the technological time trend alone. The prediction errors are of the order of 8 to 16%, with the lowest errors for winter wheat and spring barley. Copyright © 2000 Royal Meteorological Society