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The use of process-based modelling is increasing in most disciplines of plant science, but criteria for what is acceptable modelling work have rarely been made explicit. Unlike empirical work, modelling does not provide direct information on nature, and the goal is generally to explain natural phenomena, or predict their consequences, rather than reveal new phenomena or test specific hypotheses. Goals, methods and results of modelling and empirical work thus differ and they should be judged by different criteria. This note shows how the four criteria of explanation, testability, novelty and good modelling practice can be applied to modelling papers in the plant sciences. The practical implementation of these criteria is discussed, and a checklist of eight questions is derived with which papers can be evaluated. To illustrate the use of the criteria, they are applied to a classic publication from the crop modelling literature [Simulation of Assimilation, Respiration and Transpiration of Crops. Pudoc, Wageningen]. [Copyright &y& Elsevier]

Abstract: Previous QTL studies on seedling vigor in rice (Oryza sativa L.) were conducted all based on laboratory germination tests. In the current study, a set of recombinant inbred lines derived from a rice cross were assessed for seedling vigor related traits in natural field environments including two treatments (drained soil and flooded soil). Composite interval mapping identified nine QTL for seedling vigor traits that correlated positively with each other. Individual QTL explained 4–14% of the total trait variation. Among the QTL, three and four were specific to the drained and flooded treatments, respectively, while two others were common between the two treatments. Four QTL (qFV-1-1, qFV-3-2, qFV-5-1 and qFV-10) each simultaneously showed effect on two or more traits with additive effects always in the same direction. The QTL qFV-5-1 could be further resolved into at least two linked loci, qFV-5-1a controlling seedling height and qFV-5-1b controlling seedling dry weight while the QTL qFV-10 could be a single locus with a pleiotropic effect on both seedling height and dry weight. The QTL qFV-1-1 and qFV-3-2 expressed specially under the flooded conditions, each pleiotropically controlling both coleoptile and seedling emergence. These two QTL were completely different from that affecting seedling emergence in the drained conditions. Comparison of the QTL indicated that the QTL mapping results based on field assessments could to some extent coincide with those based on lab tests but the discrepancy between the two kinds of experiments could not be overlooked. [Copyright &y& Elsevier]

Meta-analyses have highlighted several advantages of cereal/legume intercropping for food compared to sole cropping, but none report on fodder quality and yield. In forage production, mixtures may more effectively balance fiber and crude protein concentrations of the forage in view of nutrient requirements of ruminants than sole crops. However, productivity, quality and the trade-off between these in cereal/legume intercropping of fodder species have not been systematically reviewed. This paper reports on a meta-analysis of a database of global literature on intercropping of forage-producing cereal and legume crops to evaluate the effect of intercropping on dry matter (DM), crude protein (CP), acid detergent fiber (ADF), neutral detergent fiber (NDF), non-CP non-NDF yields and concentrations of intercrops as compared with the respective sole crops. A literature search was carried in Web of Science searching in 'all fields' with as search terms: (intercrop* OR "mixed crop*" OR "crop mix* " OR "mixed cultivation*" OR "polyculture*" OR "row crop*") AND (forage OR fodder) AND (quality OR "nutri* content" OR "nutri* concentration" OR "nutri* value"). Out of the 759 papers further selection yielded a database based on 61 publications on cereal/legume intercropping reporting total biomass and at least one quality component for both sole crops and their intercrops. The net effects for DM (1.76 ± 0.38 Mg/ha), CP (0.20 ± 0.05 Mg/ha), NDF (1.01 ± 0.25 Mg/ha), ADF (0.63 ± 0.15 Mg/ha) and non-CP non-NDF (0.76 ± 0.22 Mg/ha) yields showed production of all increased upon intercropping. The difference in relative increase in total DM and the four components did not lead to any change in %CP, %NDF, %ADF and %non-CP non-NDF. The change in DM yield was due to enhanced cereal yield. Moreover, the cereal %CP in the intercrops was higher than expected and the cereal %NDF and %ADF in the intercrops was lower than expected, while the overall quality of the legume in the intercrops did not change. Intercropping cereal and legume species will neither improve nor reduce the quality of produced feed, but it makes more effective use of the land through a higher production per unit area. This study reports the combined forage quality and quantity in cereal/legume intercropping. The quantity/quality balance of forage production with cereal/legume intercrops is necessary to design intercropping for forage production. The results can be utilized to establish cereal/legume intercropping systems with different forage production aims. • This meta-analysis reports fodder yield and quality of grass/legume intercrops. • Average net effect for yield was 1.76 ± 0.38 Mg/ha with no change in overall quality. • The yield and quality of the cereal component increased compared to its land share. • The yield and quality of the legume did not differ from its land share. [ABSTRACT FROM AUTHOR]

After over 20 years of practicing shallow rotary tillage combined with straw direct return in the middle and lower Yangtze regions of China, the yield potential has gradually disappeared, and new alternative tillage practices are required to continuously increase rice yield. This paper investigates the yield effect and mechanism of deep tillage combined with straw return through two consecutive years of a field experiment. Three tillage depths (shallow tillage 6–7 cm, ST; medium tillage 12–14 cm, MT; and deep tillage 25–28 cm, DT) plus three straw management methods (no straw return, NR; straw direct return, SR; and straw biochar return based on the same amount of carbon input as SR, BR) were set up as experiment treatments. The aboveground and belowground growth traits of rice and soil nitrogen (N) status were determined. Compared with ST and MT, the DT enlarged rice root distribution and increased soil N content in the middle and lower soil layers (7–28 cm) and decreased the root–shoot ratio at the flowering stage, which was conducive to absorbing more soil nutrients from the subsoil and allocating more photosynthetic products to the aboveground parts and grain. The MT and DT increased spike number and rice yield compared with ST. Compared with NR, both SR and BR increased soil total and available N contents, and the remaining soil available N content at the harvest stage of BR was lower than that of SR. Straw return (SR and BR) improved rice yield by increasing spike number and kernels per spike, and the effect of BR on increasing rice yield was greater than that of SR. The DT combined with BR increased root distribution and N content in the subsoil, promoted the utilization of subsoil's nutrients, and increased rice yield. It is therefore a promising tillage practice for achieving high rice yields. • DT increased root distribution and N content in the subsoil. • DT had the lowest root-shoot ratio, allocating more biomass to aboveground growth. • DT increased spike number and straw return increased spike number and kernels per spike. • DT combined with BR is a promising approach for increasing rice yield. [ABSTRACT FROM AUTHOR]

Mungbean, a grain legume with high nutritional value, is grown widely throughout Asia and increasingly in Australia. Despite growing interest amongst farmers, mungbean remains an inconsistent and thus risky crop to plant in Australia. Cropping system models like the Agricultural Production Systems sIMulator (APSIM) are valuable tools for helping farmers to examine options for improving crop management and assess production risks across potential growing regions for mungbean. This paper outlines the simulation capacity of a new mungbean crop model parameterized using the Plant Modelling Framework in APSIM Next Generation, the newest version of the APSIM framework. The aim of the paper is to document the parameterization and validation processes of the model. The new mungbean model was built using data from 28 field experiments to simulate measured phenology, canopy development, biomass accumulation/partitioning, stress responses, N fixation, root growth, and yield across a wide range of environments. The root mean squared error (RMSE) in predictions for grain weight and aboveground weight were 25.4 g m−2 and 91.4 g m−2, respectively. The model successfully captured the dynamics of crop response to sowing dates, water/irrigation regimes, and climate. The new mungbean model is a robust and accurate tool for use in Australia and tropical/sub-tropical Asia. Researchers can use the new mungbean model to determine best management practices such as the optimal time to sow mungbeans in different environments. The output from model simulations can help farmers assess risks associated with sowing at different times and soil water conditions specific to their region. Such risk analysis can improve farmer decision-making confidence in mungbean, increasing its potential production for Australia. Overall, the new APSIM mungbean model can be used effectively to identify and close the mungbean yield gap, mitigate risk of crop failure, and increase profits for mungbean farmers in Australia and tropical/sub-tropical Asia; it has the capacity to assist with increasing mungbean production globally under changing climate conditions. • The APSIM Next Generation mungbean model was built using data from 28 diverse field experiments. • Detailed phenology, biomass and N partitioning, and canopy data was used to parameterize parameters. • The model captures mungbean's dynamic response to water stress and targeted irrigation. • It is a robust, data-driven crop model that performs well in Australia and tropical/subtropical Asia. [ABSTRACT FROM AUTHOR]

Climate change implies higher frequency and magnitude of agroclimatic extremes threatening plant production and the provision of other ecosystem services. This review is motivated by a mismatch between advances made regarding deeper understanding of abiotic stress physiology and its incorporation into ecophysiological models in order to more accurately quantifying the impacts of extreme events at crop system or higher aggregation levels. Adverse agroclimatic extremes considered most detrimental to crop production include drought, heat, heavy rains/hail and storm, flooding and frost, and, in particular, combinations of them. Our core question is: How have and could empirical data be exploited to improve the capability of widely used crop simulation models in assessing crop impacts of key agroclimatic extremes for the globally most important grain crops? To date there is no comprehensive review synthesizing available knowledge for a broad range of extremes, grain crops and crop models as a basis for identifying research gaps and prospects. To address these issues, we selected eight major grain crops and performed three systematic reviews using SCOPUS for period 1995–2016. Furthermore, we amended/complemented the reviews manually and performed an in-depth analysis using a sub-sample of papers. Results show that by far the majority of empirical studies (1631 out of 1772) concentrate on the three agroclimatic extremes drought, heat and heavy rain and on the three major staples wheat, maize and rice (1259 out of 1772); the concentration on just a few has increased over time. With respect to modelling studies two model families, i.e. CERES-DSSAT and APSIM, are clearly dominating for wheat and maize; for rice, ORYZA2000 and CERES-Rice predominate and are equally strong. For crops other than maize and wheat the number of studies is small. Empirical and modelling papers don’t differ much in the proportions the various extreme events are dealt with – drought and heat stress together account for approx. 80% of the studies. There has been a dramatic increase in the number of papers, especially after 2010. As a way forward, we suggest to have very targeted and well-designed experiments on the specific crop impacts of a given extreme as well as of combinations of them. This in particular refers to extremes addressed with insufficient specificity (e.g. drought) or being under-researched in relation to their economic importance (heavy rains/storm and flooding). Furthermore, we strongly recommend extending research to crops other than wheat, maize and rice. [ABSTRACT FROM AUTHOR]

Cotton (Gossypium hirsutum L.) is one of the most salt-tolerant cash crops in the arid zone of Central Asia, especially in Xinjiang (XJ), China. Phosphorus (P) deficiency is one of the major yield-limiting factors for cotton production in this region. Although a high-chemical-P fertiliser input ensures high yields, only 18% of P can be taken up by crops in the application season, leading to large economic losses for farmers and accelerating the depletion of non-renewable P resources. It is a great challenge to optimise P inputs, increase P use efficiency (PUE) and maintain high yields under mulched fertigation cotton production systems. This paper aims to review the current efforts to improve PUE for cotton production in XJ and to provide feasible insights into nature-based solutions for high-P utilisation of cotton in the future. We focused on the following: (ⅰ) identifying the main factors that lead to the low PUE of cotton in XJ and the potential influencing mechanisms, (ⅱ) exploring innovative P management options to maximise the biological potential for improving high-P utilisation and reducing soil P surplus in mulched fertigation cotton production systems, (ⅲ) providing future perspectives of high P utilisation in mulched fertigation cotton production systems. We conducted a systematic literature search on the Web of Science and China National Knowledge Infrastructure (CNKI) to review publications that are related to the topic of cotton yield and P utilisation under different P management practices with field experiments in XJ. On the basis of the research, we proposed new insights into improving P management practices in mulched fertigation cotton production systems. We found that the soils exhibited a significant capacity for P fixation with high pH and carbonate content in XJ, leading to poor P migration when drip-irrigated. A mismatch between P fertiliser types and soil crop systems further hindered P absorption by cotton. Moreover, excessive P application and limited biological processes for soil P cycling impeded improvements in PUE. Therefore, we emphasised the importance of the root/mycorrhizal pathway in cotton P uptake and suggested using the high mycorrhizal dependence and P-efficient cotton genotypes, maximising the biological potential of the root morphology, mycorrhizal symbiosis, P-solubilising microorganisms and microbial biomass P (MBP) pool turnover in soil P mobilisation, which could increase cotton P uptake and PUE. Furthermore, we proposed a strategy of using starter P combined with ammonium sulfate fertigation after the plant emergency, and concentrated application of acidic P fertiliser with the pursuit of ammonium sulfate could achieve high cotton yields and P fertiliser efficiency. We also highlighted the potential of organic amendments in enhancing soil P bioavailability and P recycling by enlarging the MBP pool and improving the alkaline phosphatase activity, thus improving cotton P uptake and yield. Finally, we noted that nature-based solutions, which were commonly neglected in previous studies, should be integrated into zero-P surplus management strategies to maximise the biological potential for high-P utilisation in cotton production. The use of organic amendments enhanced the biological potential for the high-P utilisation of cotton. Combining starter P fertiliser with ammonium sulfate induced rhizosphere acidification and increased cotton yields and PUE. In addition, integrating nature-based solutions into zero-P surplus management strategies can increase cotton PUE and can maintain a high yield by maximising the biological potential for high-P utilisation. Overall, developing novel P management practices to optimise nature-based soil P cycling and to improve the biological potential for zero-P surplus can maximise the high yield and can underpin sustainable cotton production in an arid zone. • Starter P combined with ammonium sulfate fertigation can increase cotton yield and PUE. • Organic manure enhances the biological potential for high-P utilisation of cotton. • Innovative P management strategies can increase cotton PUE and maintain a high yield. • Zero-P surplus practice will focus on nature-based solutions in cotton production systems. [ABSTRACT FROM AUTHOR]

Excessive fertilization reduces fertilizer efficiency and farm economic benefits, and causes various environmental problems. This study aimed to produce high grain yield and protein content for wheat production in China using a High Nutrient-use efficiency Based Fertilizer Recommendation method (High NUFER) and limits for crop nutrient physiological efficiency and partial factor productivity of fertilizer. A farm survey covering 1575 fields was carried out in 17 major wheat production provinces in China from 2015 to 2019. The on-farm information included wheat planting area, varieties, field management, soil nutrient status and fertilization status, and wheat plant and soil samples were also collected from farmers' fields for measurement and analysis. The High NUFER proposed in this paper was verified in 46 sites in 7 major wheat production provinces from 2020 to 2021. For the average grain yields > 6.0 t ha–1 and protein content ∼13.0% in major wheat production regions of China, the nutrient physiological efficiency of wheat should range from 36.5 – 36.8 kg kg–1 nitrogen (N), 261.3–273.9 kg kg–1 phosphorus (P), and 53.0–54.3 kg kg–1 potassium (K), and partial factor productivity of N, P, and K fertilizers should range from 35.9 – 41.9, 153.5–177.9, and 132.5–158.9 kg kg–1, respectively, when soil available nutrients ranged from 19.0 to 21.8 mg kg–1 available N (nitrate-N + ammonia-N), 22.4–26.1 mg kg–1 available P, and 153.9–157.3 mg kg–1 available K. Using the High NUFER, China should save 0.62 MT yr–1 N fertilizer, 0.36 MT yr–1 P fertilizer, and 0.22 MT yr-1 K fertilizer, with an additional economic benefit of 1.1 billion USD yr–1 and reduction in greenhouse gas (GHG) emissions of 8.91 MT CO 2 eq yr–1 in major wheat production regions. The High NUFER can reduce farmers' fertilizer input, thereby increasing economic benefits and decreasing GHG emissions. The High NUFER proposed in this paper has practical value for nutrient management in China and is a potential reference for other wheat-growing countries. • Limits were set for crop nutrient physiological efficiency and partial factor productivity of fertilizer at national scale. • Study offers the possibility of producing high yields with high protein content. • Established yield-protein content and nutrient efficiency relationships at a national scale. [ABSTRACT FROM AUTHOR]

Nitrogen (N) is an essential nutrient for crop growth, and its different forms have a significant impact on crop uptake and various physiological processes that underpin yield and quality. Although many studies suggesting that a combination of ammonium (NH 4 +) and nitrate (NO 3 -) can enhance crop outcomes, the optimal ammonium-nitrate ratio (ANR) for different crops remains uncertain due to a lack of extensive validation with large datasets. This paper collected 151 peer-reviewed studies (with 2417 observations) on the effects of ANR on crop growth published from 1972 to 2022. The comprehensive effects of different ANRs on crop yield and quality (protein, vitamin C, starch etc.) of various crops were evaluated via meta-analysis to provide an optimal N management strategy. Our analysis identified rice as an ammonium-preferred crop, and the ANR of 75:25 shows the most effective improvement in total biomass and photosynthetic characteristics at seedling age, with a 26.0% increase in the biomass and a 21.9% boost in chlorophyll content compared to pure ammonium treatment. Wheat and tobacco can be considered ammonium-nitrate-balanced crops, and a balanced ANR of 50:50 resulted in significant synergistic improvement in both yield and quality, i.e., wheat biomass and protein increased by 13.3% and 7.1%, respectively, and tobacco yield significantly increased by 21.9%, compared to pure nitrate supply. In contrast, maize, soybeans, and vegetables were identified as nitrate-preferred crops, applying pure ammonium or an excess of ammonium-N over nitrate led to a significant reduction in yield and quality, with the most pronounced inhibitory effect observed in soybeans. However, a slight supplement of ammonium can also promote the growth of these crops. Furthermore, soil pH significantly influences the preference for ammonium and nitrate. In soils with an acidic environment, crops tend to efficiently utilize nitrate, whereas in alkaline conditions, there is a preference for an increased presence of ammonium. The combination of ammonium and nitrate in appropriate ratio can improve multiple agronomic characteristics both for ammonium-preferred and nitrate-preferred crops, which may due to complementary physiological functions of two forms of N. Among various soil factors, soil pH showed significant influence on determining the optimal ANR and should be taken into consideration. These findings reveal that the appropriate ANR is crucial for both crop yield and quality improvement and should be fully valued in future nutrient management. • Rice is an ammonium-preferred crop with optimal ANR of 75:25. •.Wheat and tobacco can be considered ammonium-nitrate-balanced crops. •.Maize, soybeans, and vegetables are nitrate-preferred crops. • Soil pH greatly affects the ammonium-nitrate preference. • Appropriate ANR is crucial for both crop yield and quality improvement. [ABSTRACT FROM AUTHOR]

Conventional high-density planting of machine-picked cotton in Xinjiang is associated with poor light distribution and low fiber quality. The objective of this study was to assess how different row spacing configurations, irrigation rates, and planting densities impact cotton photosynthetic production and fiber quality. We conducted a 3-year field experiment in Shihezi, Xinjiang, China, to evaluate the impact of different row spacing configurations and irrigation amounts on cotton photosynthesis and fiber quality. The four row spacing configurations used were: RS 66+10 H (high-density with 66 +10 cm spacing), RS 66+10 L (low-density with 66 +10 cm spacing), RS 76 H (high-density with 76 cm spacing), and RS 76 L (low-density with 76 cm spacing). Additionally, two irrigation amounts were tested: MD-T 3 (mulch drip irrigation with three tapes on one film) and MD-T 2 (mulch drip irrigation with two tapes on one film). We measured and compared the distribution of cotton canopy leaves, light, canopy apparent photosynthesis, reproductive organs and fiber quality among these groups. The results showed that RS 66+10 H had a higher lint yield than RS 76 L under MD-T 2 , with an increase of 5.4–7.1%. This can be attributed to the higher fraction of photosynthetically active radiation, canopy apparent photosynthesis (CAP), and boll biomass in RS 66+10 H between the full boll and boll opening stages. The maximum lint yield (3227–3580 kg ha−1) was obtained in RS 66+10 H under MD-T 3. Interestingly, RS 76 L had a similar lint yield to RS 66+10 H under MD-T 3 , mainly due to the middle and lower canopy having higher leaf area index (LAI) values ranging from 1.8 to 2.1. This resulted in increased CAP and cotton boll biomass of the middle and lower canopy compared to RS 66+10 H during the full boll to boll opening stage. Under MD-T 3 , RS 76 L also exhibited longer fiber length in the middle and lower canopy (30.2–32.0 mm and 31.6–33.3 mm, respectively) compared to RS 66+10 H, with a difference of 3.2–3.8% and 5.6–6.5%. Furthermore, RS 76 L demonstrated higher fiber strength in the middle and lower canopy (31.4–32.7 cN tex−1 and 33.2–33.9 cN tex−1, respectively) compared to RS 66+10 H, with a difference of 2.6–6.2% and 5.9–6.8%. Maintaining an LAI of around 2.0 during the transition from full boll to boll opening stage optimized canopy architecture and enhanced photosynthetic productivity. Under adequate irrigation, RS 76 L could be a suitable replacement for RS 66+10 H in order to improve cotton fiber quality by optimizing leaf-boll spatial distribution. This study provides guidance for selecting the appropriate row spacing configuration under different water conditions. RS 66+10 H is recommended for increasing yield under water-deficient conditions, while RS 76 L is suitable for improving fiber quality under adequate irrigation. [Display omitted] • Conventional high-density planting has poor fiber quality. • RS 76 L under adequate irrigation maintained high cotton yield and improved fiber quality. • Around 2.0 of LAI in the middle and upper canopy can maintain high photosynthetic rate. • RS 76 L maintained high yield and improved quality by optimizing leaf-boll spatial distribution. [ABSTRACT FROM AUTHOR]

In the past 50 years, rice has become an important crop for food security in sub-Saharan Africa. However, rice yields remain relatively low, and large yield gaps exist. This Special Issue brings together agronomy research on rice-based farming systems in sub-Saharan Africa and addresses three main, overarching questions: (1) what has been achieved in the past decades in terms of rice agronomy in sub-Saharan Africa, (2) what is the state-of-the-art regarding development of technologies and (3) what will be likely or required future directions? The broad topics included in this Special Issue are (1) yield trends and yield gap analyses, (2) soil & nutrient, water, weed and integrated crop management practices, (3) cropping systems, (4) genetic improvements, (5) crop simulation modeling, and (6) assessment of farmers' rice cultivation practices and the sustainability of these practices. The papers cover different sub-regions, from the Sahel to the highlands of Madagascar and three major rice growing environments (irrigated lowlands, rainfed lowlands, and rainfed uplands). In this paper we describe the major challenges in the rice production sector in sub-Saharan Africa and historical efforts on agronomy research, and we provide a short introduction and discussion on the papers presented in this Special Issue. This Special Issue arrives at six main recommendations. 1. There is a need to increase research and development efforts focusing on rainfed rice-based systems. 2. More attention needs to be paid to research on the farming system or landscape level, aimed at development of integrated cropping and farming systems and integrated agronomic solutions. 3. Current and future agronomic rice research should thematically center around sustainability, including judicious natural resources management, climate change adaptation and mitigation, and conservation of biodiversity and environments. 4. To operationalize this, sustainability performance indicators need to be developed and used. 5. There is broad consensus regarding the need for more labor-saving technologies, including mechanization options, provided these do not increase the ecological footprint of production systems. 6. Future rice agronomy research work should be interdisciplinary and transdisciplinary, to better address the myriad of challenges of smallholder farmers in Africa. Papers presented in this Special Issue should inform on the state-of-the art in rice agronomy in SSA, and on ways to sustainably enhance rice production and self-sufficiency in this region. • A Special Issue on rice agronomy research in Africa recommends future research to. • Focus on the dominant rainfed systems and develop labor-saving technologies. • Consider farming systems, landscape level issues and integrated cropping systems. • Focus on sustainability and develop and use sustainability performance indicators. • Work in partnership with non-agronomy researchers and non-research stakeholders. [ABSTRACT FROM AUTHOR]

Maize (Zea mays L.) prolificacy (i.e., more than one fertile ear per plant) is a source of reproductive plasticity that contributes to increase or sustain crop grain yield when plant density is reduced in drought-prone environments. The rare use of N fertilization, however, can limit prolificacy. In a companion paper we studied floret differentiation and biomass allocation in apical (E1) and sub-apical ear (E2) and flowering dynamics of five maize hybrids with contrasting prolificacy under different plant densities and N supplies. Briefly, after apex induction, E1 and E2 of the most prolific hybrids (DK-3F22, DK-4F37 and DK-664) had similar temporal patterns of growth and floret differentiation. On the contrary, E2 in the less prolific hybrids (DK-747 and DK-7210) had less biomass allocation and floret differentiation than E1, which were reduced under low soil N supply, resulting in a fewer proportion of plants with silk extrusion of E2. In this work, we explore the relationships between (i) kernel number per plant vs the growth rates of plants around flowering, (ii) growth rate of ears vs plant growth rate around flowering (i.e. biomass partitioning to E1 and E2), (iii) kernel number of E1 and E2 vs the growth rates of ears around flowering (i.e. reproductive efficiency of E1 and E2), and (iv) kernel number and prolificacy vs flowering synchrony (i.e., ASI: anthesis-silking interval and ESI: ear silking interval between E1 and E2). For all hybrids, N supply modulated plant growth rate and biomass partitioning to both ears around flowering, kernel number per unit of plant growth rate around flowering and reproductive efficiency of E2, with no impact on the reproductive efficiency of E1. Reductions of kernel number per plant were related to failures of early emerged silks (of E1 under low N supply and of E2 under both N supplies) to set kernels. Failures in kernel setting of E2 were also related to a reduced biomass partitioning to E2 around flowering. Higher ASI E1 values described crops with lower kernel numbers of E1, while higher ESI values depicted both a lower proportion of plants with more than one fertile ear (i.e., prolificacy) and lower kernel numbers of E2. Results complement evidence from the companion paper of the role of N supply on plant biomass production and biomass partitioning to E2 from early floral development stages to the period around flowering, and on the reproductive efficiency of E2. Consequently, N supply must be ensured from early vegetative stages of low-density maize crops, so as not to compromise prolificacy and E2 kernel setting. • Prolificacy was highly sensitive to N supply even at low plant density. • High N supply increased biomass partitioning to ears around flowering. • Only reproductive efficiency of sub-apical ear (E2) was improved by N supply. • Ear silking interval modulate prolificacy expression and kernel setting of E2. [ABSTRACT FROM AUTHOR]

The current pace of yield increase for major crops is not fast enough to meet future demand. Crop breeding programmes are under increasing pressure to improve existing crops further. Quantifying the contribution of these programmes to observed yield increases is important for evaluating their success and identifying if crop improvement goals are likely to be met. In this paper we explore methods to study the genetic gain of two cereal species, wheat (Triticum aestivum L.) and barley (Hordeum vulgare L.). Specifically, the objective of this research was to identify sources of bias in genetic gain estimates of UK variety trials data. Genetic gain was estimated for fungicide-treated and untreated UK winter wheat, winter barley and spring barley for 1982–2018 using UK National List and Recommended List variety trials data. Subsets of the winter wheat variety trials dataset were used to replicate shorter breeding cycles to quantify the impact of the number and choice of long-term check varieties on estimating genetic gain. While genetic and non-genetic contributions to changes in UK cereal performance are in line with previous estimates, we were able to identify previously undetected changes and biases in estimates of variety performance. Specifically, we observed an increasing yield difference between fungicide treated and untreated variety trials as varieties age, driven by both a breakdown in disease resistance and a previously unobserved long-term increase in yield as varieties age in treated trials. This shows that yields of long-term check varieties cannot be assumed to be stable over time. We found that genetic gain estimates were highly sensitive to the long-term check varieties chosen, whilst the inclusion of multiple checks decreased the standard error of the estimate. The estimation of genetic gain is highly susceptible to bias. We provide recommendations on how to reduce the risk of bias for estimating genetic gain. Accounting for sources of bias in genetic gain calculations is important in any programme of selection to prevent inaccurate quantification of yield progress. • Recent yield plateaus in major crops are reducing the likelihood of meeting future food security. • To direct research investment, accurate quantification of yield progress is required. • The estimation of genetic gain is highly susceptible to bias. • Sources of bias include disease resistance breakdown and instability in long-term variety yields. [ABSTRACT FROM AUTHOR]

Barley is one of the most relevant crops worldwide and an essential component of agriculture in Europe in general, and in the Mediterranean region in particular. As cropping areas will hardly rise in the future, yield must be improved to enhance global crop production. Naturally, understanding how yield is affected by environmental and genetic factors in two- and six-rowed barley can help us to develop more efficient management and breeding strategies to increase current yield gains. We aimed to determine the relative importance of genetic and environmental factors on numerical and physiological components of GN for two- and six-rowed barley types. To generate a large and unbiased database, we compiled data of yield and its numerical and physiological components from crop-based experiments (i.e., excluding controlled-conditions experiments and/or approaches using isolated plants) reported in figures and tables in every single paper having the word "barley" in the title published over 25 years in four rigorous and prestigious international journals: Field Crop Research, European Journal of Agronomy, Crop Science and Crop and Pasture Science (formerly Australian Journal of Agricultural Research) between January 1996 and December 2021, both inclusive. Spike number (SN) was the most relevant numerical component explaining GN regardless of the source of variation. Regarding physiological components, it seemed that when the driving force was environmental factors, spike dry weight at flowering (SDW F) was more relevant than fruiting efficiency (FE); whilst when the differences were due to genotypic factors, clearly the FE was the component mostly responsible for the changes in GN. When the analysis was restricted to two- and six-rowed barley types, GN improvements were mainly explained by changes in SN for both two- and six-rowed barley types. However, when the physiological components were considered, the responsiveness of GN was more related to SDW F than to FE in two-rowed genotypes, while the opposite was true for the six-rowed type. In barley, SN always explained the responses of GN better than grain number per spike (GNS), regardless the source of variation and the type of barley. Respect to the physiological components, environmental factors affected GN mainly through affecting SDW F , while genotypic factors affected GN through affecting FE. SDW F and FE were more relevant for explaining changes in GN two- and six-rowed barleys, respectively. Breeders and agronomists can be aware that it will be more likely to achieve significant gains in yield through focusing more on SN than on GNS regardless of the barley type, whilst regarding the physiological components it would be more relevant to focus on SDW F in two-rowed barley, and on FE in six-rowed barley. • We quantified grain number components depending on source of variation in barley. • Spike number (SN) explaining grain number regardless of the source of variation. • Spike dry weight (SDW F) was the most relevant component for environment factor. • Fruiting efficiency was more relevant for genotypic factor. • Grain number was more related to SDW F in two-rowed, while FE in six-rowed type. [ABSTRACT FROM AUTHOR]

The nitrogen economy of the crop is a critical driver of biomass and grain production, and its importance is reflected in a large, worldwide research effort to link nitrogen, growth and yield. Particular research questions require measurement of specific traits, hence the need to quantify multiple, often complementary traits including crop nitrogen uptake, nitrogen use efficiency and its components, nitrogen concentration in the crop and its parts, down to relevant enzymes (e.g. nitrate reductase) and other products of gene expression. Nitrogen uptake, however, is co-regulated by both soil nitrogen availability and crop biomass accumulation; hence, crop nitrogen uptake or shoot nitrogen concentration reflect univocally crop nitrogen status only if comparisons are made at similar biomass. Although the allometric relationships between biomass and nitrogen uptake have been established for over two decades, many studies still report results in terms of nominal treatments, e.g. high vs low nitrogen, which are uninformative; curves relating yield and fertiliser rate, which are of local interest but provide little insight on the underlying processes and have low generic value; and nitrogen-related traits that are incomplete or inadequate to quantify crop nutrition status. Often, the allometric relationships between nitrogen and biomass are overlooked. In this opinion paper, we summarise the already well established concepts of dilution curves and nitrogen nutrition index, outline the standard partitioning of nitrogen use efficiency, and highlight the confounded effects in nitrogen use efficiency when the allometric relationship between nitrogen uptake and biomass is ignored. A sample of recent papers is used to survey the most common approaches to characterise nitrogen related traits. We illustrate the application of dilution curves and nitrogen nutrition index in the assessment and interpretation of crop responses to agronomic practices and comparisons of wheat cultivars and maize hybrids. [ABSTRACT FROM AUTHOR]

Abstract: Mixed crop–livestock farming systems prevail in Mexico – typically rain-fed and smallholder systems based on maize and ruminants and spanning diverse agro-ecologies. Maize grain is the key Mexican staple produced for home consumption and the market. Maize crop residues (stover) are an important by-product, primarily for feed use, often through in situ stubble grazing and/or as ex situ forage. This paper explores maize stover use along the agro-ecological gradient and the potential trade-offs, particularly the widespread use of maize stover as feed against its potential use as mulch (soil cover) to manage soil health within the context of conservation agriculture. The paper builds on three case study areas in Mexico in contrasting agro-ecologies: (semi-)arid, temperate highland and tropical sub-humid. Data were obtained through expert consultation and semi-structured farmer group/community surveys. Although in situ grazing is found in all three study sites, it represented the bulk of stover use in only one site (70% of stover in the sub-humid tropics), with ex situ feed dominating in the other two sites (>80%). Maize stover commercialization is limited and mainly restricted to households with no livestock and often within the local context. Farmers are generally hesitant to adopt conservation agricultural practices that require the retention of stover as mulch, as this competes with their livestock feed needs and purchased feed is expensive. To reduce trade-offs, a portfolio of options could be adapted to these mixed systems, including partial residue retention, cover and feed crops and sustainable intensification. Promising but yet to be explored, are investments in the genetic improvement of maize stover feed quality. [Copyright &y& Elsevier]

Abstract: Crop growth and production are dependent not only on the amount of total nitrogen (N) absorbed by plants, but also on the vertical leaf N distribution within canopies. The non-uniform leaf N distribution has been reported for various plant canopies. Remote sensing has been widely used for determination of crop N status, but such analysis seldom takes N distribution into consideration, ultimately leading to limited accuracy and decreased practical value of the related results. This paper has reviewed the results of previous studies that investigated the ecophysiological aspects of non-uniform N distribution, and the remote sensing methods that have been proposed to monitor this phenomenon. Additionally, this study used field data to analyze the differences in leaf N distribution in wheat canopies with different plant types (i.e. spread type, semi-spread type, and erect type), and provided insights into the estimation of vertical leaf N distribution by means of remote sensing. The process of reviewing research related to the ecophysiological issues of leaf N distribution led to identification of several important inadequacies in the current body of research. We propose that future work should aim to strengthen an understanding of the dynamic response of vertical N distribution within canopies to the various related environment factors and field management strategies. When a more thorough understanding of vertical N distribution is achieved, researchers will be able to improve related quantitative modeling, and may be able to comprehensively reveal the effect of vertical N distribution on canopy photosynthesis performances. In addition, through a comparison of the leaf N profiles of spread, semi-spread, and erect wheat canopies, it was found here that the semi-spread wheat canopy had a more non-uniform N distribution than did the other two types, despite all types having large and full vegetation coverage at the booting stage. Regarding detection of leaf N distribution using remote sensing, the few existing studies can be grouped into three classes according to the hyperspectral data used. One class employed the spectral data obtained from top-view observations; another class used multi-angle canopy reflectance data, while the third mainly focused on the relationships between spectral reflectance and fluorescence characteristics and the leaf N or chlorophyll content for different vertical layers. Despite important progress having been made, the results of the studies and the methods therein face key limitations in practical application. The present paper suggests two possibilities for the estimation of vertical leaf N distribution with remote sensing. One possibility is based upon hyperspectral imaging, and the other possibility combines a vertical N distribution model and canopy reflectance data. The former method requires investigation of the ability of hyperspectral imaging to obtain pure spectral information of different vertical leaf layers. The latter method requires that the key determinants of vertical N distribution be identified to improve quantitative modeling, and that the parameters of the N distribution model be determined from remotely sensed data. Because of the current lack of adequate data, a concrete case study and a very thorough test analysis could not be presented here. But it is still hoped that this work can provide helpful information for future studies. [Copyright &y& Elsevier]

Abstract: Moroccan agriculture is characterized by the co-existence of both modern and smallholder traditional agriculture. Both types of agriculture are under degradative processes due to mis-use of tillage implements, mis-management of crop residues and inappropriate links between grain and livestock productions. From the research conducted over the last three decades, the vast majority of beneficial tillage effects are transient. Conversely, the harmful effects of conventional tillage (CT) systems are long-lasting, if not permanent. The present paper aims at evaluating major achievements in conservation or no-tillage agriculture (CA or NT) research conducted in dry areas of Morocco and presenting important ways to implement these achievements within the Moroccan rural society. CA has been introduced in response to issues of soil conservation, drought mitigation and soil quality management. NT systems have resulted in reduced soil erosion, greater soil water conservation, improved soil quality and stable and higher crop yields. Changes in crop production practices due to shifting to NT or CA systems and retention of crop residues at or near the surface produced progressive qualitative and quantitative variations in soil organic matter. This can allow agriculture to contribute to country''s efforts to reduce and control greenhouse gas emissions. These effects benefited both farmers and society in terms of higher returns and efficiencies. Under NT, benefits from improved agriculture''s environmental performance must be added to remunerations of reducing costs of production and improving well-being of farmers. The other strong benefits that CA brings come from the opportunity for early sowing and savings in time, machinery and fuel. Even though, many agronomic, socio-economic and environmental benefits accrue from NT and increasing crop diversity; lack of incentives from the government and social factors encourage the continued use of CT systems. CA systems were sufficiently tested in research stations but found limited adoption in farm communities. The shift in the late nineties to more on-farm research did not result in the envisaged breakthroughs, mainly due to poor research-extension linkages and several social and technical barriers. Consequently, in order to realize durable agricultural growth, there is a huge challenge to out- and up-scale CA in Morocco through linkage of all stakeholders (farmers, developers, researchers, industrials and policy makers). This paper fulfills information gaps and presents a thorough discussion on constraints to CA adoption as well. [Copyright &y& Elsevier]

Abstract: Several papers reported that the incorporation of Bt genes into rice caused morphological and physiological changes. In this paper, we try to reveal whether the incorporation of a Bt gene (cry1C* or cry2A*) into Minghui63 (MH63) and Shanyou63 (SY63) will affect the yield performance, and its agronomic and physiological mechanism underlying the yield differences. Field experiments were conducted in 2009 and 2010 at Zhangbang village, Wuxue city (29°51′N 115°33′E) and Dongshantou village, Xiaonan county (30°56′N 113°54′E), Hubei Province, China from May to October. Treatments were arranged in a randomized complete block design with three replications, and each replication contained three genotypes in 2009 and six genotypes in 2010. No significant differences in grain yield, biomass, leaf area index (LAI), nitrogen accumulation and growth-promoting phytohormones content were observed between MH63 (cry2A*) and MH63, except that MH63 (cry2A*) had significantly lower grain yield than MH63 at Wuxue city in 2009. MH63 (cry1C*) had lower grain yield than MH63 and MH63 (cry2A*) at all site-years, and the yield reduction was mainly ascribed to the reduced grain filling percentage. Growth analysis revealed there were no differences in biomass production and nitrogen accumulation between MH63 (cry1C*) and MH63. The incorporation of cry1C* brought a significant reduction in the content of growth-promoting phytohormones in the superior spikelets, which highly correlated with grain filling percentage of MH63, MH63 (cry1C*) and MH63 (cry2A*). There were no significant differences on grain yield and growth performance among all the three hybrids by crossbreeding MH63, MH63 (cry1C*) and MH63 (cry2A*) with Zhenshan 97A. More endeavors are encouraged to examine the physiological and genetic mechanisms behind the variations. [Copyright &y& Elsevier]

The paper compares food and straw fodder traits in wheat lines of 6 different CIMMYT wheat trials tested across 32 environments of South Asia (India, Nepal, Bangladesh and Pakistan). Experiments were conducted in the main spring wheat season with sowing time of mid-November to mid-December and harvest between March to April. Investigated and compared were grain yield (GY), straw yield (SY), straw nitrogen (N) content, neutral (NDF) and acid (ADF) detergent fiber, acid detergent lignin (ADL), and in vitro organic matter digestibility (IVOMD). Highly significant (P < 0.0001) differences were observed between cultivar types for all traits. The proportional ranges in traits between the cultivar types were high for GY and SY (>60%), considerable (45%) for HI and straw N (40%), moderate for ADL (18%), and minor for NDF, ADF, and IVOMD (<10%). Across cultivar types GY and SY were significantly positive correlated but GY accounted for only 14% of the variation in SY. Positive fodder traits such as N and IVOMD tended to be negatively associated with GY, whereas negative traits such as NDF, ADF and ADL were positively associated with GY, significantly so (P < 0.05) in the cases of ADF and ADL. Except for one case, broad sense h2 were stronger for GY than for SY. Among straw fodder quality traits, the negative fodder quality traits ADF showed the highest h2 for all quality traits, with the exception of the two drought trials. Across all cultivar types only ADF was significantly (P < 0.05) positively related to GY. No significant (P > 0.05) relationships were observed between N, ADF and IVOMD and SY. Among cultivars consistent relationships were only observed between N and GY which were significantly (P = 0.03 to 0.009) inversely correlated in five out of the six cultivar types. Within cultivars types ADF varied by at least 2.3% units in HTNM and 1st DRYT and up to 4.9% units in ESWYT. By extrapolation such cultivar-dependent differences will matter at wheat straw trading. [ABSTRACT FROM AUTHOR]

• Compared to the rest of East Africa, yields of smallholder rainfed wheat are high in Northern Rwanda. • Still, large yield gaps remain, of about 2 t ha-1 in average. • Yields could be increased by higher input use (e.g., seeds), frequent weeding and labour-saving technologies. • Resource-saving technologies appear as important as yield-increasing technology to improve wheat profitability. As wheat demand is increasing in sub-Saharan Africa (SSA), domestic production is being encouraged. The potential to increase the productivity and profitability of wheat appears large in the region, but little is known about the concrete interventions needed to meet that potential. In this study, we selected a site in Northern Rwanda (representative of the cool humid climatic zone which accounts for most of the spring wheat production of SSA) and analysed the determinants of wheat productivity and profitability for 130 smallholder farms during two consecutive short rainy seasons, namely 2017A and 2018A (wheat is seldom grown during long rainy seasons: potato is the preferred crop then). Although wheat yields were found to be high when compared to typical yields in SSA (means of 3469 and 3052 kg ha−1 during the seasons 2017A and 2018A, respectively), large yield gaps were also found (1.977 t ha−1 on average, or 37.6% of the highest farmer's yield, defined as the average actual yields above the 90th percentile of this variable). Evidences presented in the paper suggest that wheat productivity could be increased through increased seeding rate (a 0.14% increase in wheat grain yield was found with a 1% increase in seeding rate), increased nitrogen (N) application combined with frequent weeding (a 0.02% increase in wheat grain yield was found with a 1% increase in N application and frequent weeding), and labour-saving technologies (e.g., herbicides and mechanization). If wheat profitability would also increase with frequent weeding and labour-saving technologies, it would decrease with increased input use in many cases. Indeed, seed, fertilizer and amendments represent most of the wheat production cost in the area. These results illustrate the importance of assessing the impact of narrowing the yield gap on profitability, not only productivity, as some yield-increasing technologies may not be desirable from an economic perspective. They also demonstrate that resource-saving technologies (input-saving e.g., precision agriculture, labour-saving e.g., mechanization) may be as much in demand by African smallholders as yield-increasing technologies, calling for a more balanced approach in current research and development initiatives on the continent. [ABSTRACT FROM AUTHOR]

• Estimated maize yield gaps ranged between 67% and 84% of water-limited potential yield. • Demonstration experiments showed the potential of improved varieties and fertilizers. • Farmers' yields are determined by interacting, and often strongly varying, household, soil and management factors. • Integrated assessment of yield gaps using multiple methods avoids over-simplified conclusions. Agricultural production in Ghana should more than double to fulfil the estimated food demand in 2050, but this is a challenge as the productivity of food crops has been low, extremely variable and prone to stagnation. Yield gap estimations and explanations can help to identify the potential for intensification on existing agricultural land. However, to date most yield gap analyses had a disciplinary focus. The objective of this paper is to assess the impact of crop management, soil and household factors on maize (Zea mays) yields in two major maize growing regions in Ghana through an integrated approach. We applied a variety of complementary methods to study sites in the Brong Ahafo and Northern region. Farm household surveys, yield measurements and soil sampling were undertaken in 2015 and 2016. Water-limited potential yield (Y w) was estimated with a crop growth simulation model, and two different on-farm demonstration experiments were carried out in 2016 and 2017. There is great potential to increase maize yields across the study sites. Estimated yield gaps ranged between 3.8 Mg ha−1 (67% of Y w) and 13.6 Mg ha−1 (84% of Y w). However, there was no consistency in factors affecting maize yield and yield gaps when using complementary methods. Demonstration experiments showed the potential of improved varieties, fertilizers and improved planting densities, with yields up to 9 Mg ha−1. This was not confirmed in the analysis of the household surveys, as the large yield variation across years on the same farms impeded the disclosure of effects of management, soil and household factors. The low-input nature of the farming system and the incidence of fall armyworm led to relatively uniform and low yields across the entire population. So, farmers' yields were determined by interacting, and strongly varying, household, soil and management factors. We found that for highly variable and complex smallholder farming systems there is a danger in drawing oversimplified conclusions based on results from a single methodological approach. Integrating household surveys, crop growth simulation modelling and demonstration experiments can add value to yield gap analysis. However, the challenge remains to improve upon this type of integrated assessment to be able to satisfactorily disentangle the interacting factors that can be managed by farmers in order to increase crop yields. [ABSTRACT FROM AUTHOR]

Highlights • Grain yield was remarkably insensitive to plant density. • Grain yield especially in short erect types was reduced with row spacings greater than about 30 cm. • Grain yield in raised bed plantings may be biased because of the sensitivity of short erect wheats to row spacing. • The insensitivity to of grain yield low density (maximum at <20 plants/m2) suggests a new breeding startegy. Abstract This paper reviews the results of published and unpublished experiments over 30 years looking at the effect on yield of planting density and row spacing, and of raised bed planting, of modern irrigated short wheat cultivars under the favourable climatic conditions of northwest Mexico. With optimum planting dates (mid Nov. to mid Dec.), regardless of row spacing, wheat yield was remarkably insensitive to planting density within the range normally studied (80–400 plants/m2). However yield was sensitive to row spacing: the most sensitive cultivars (erect dwarf cultivars) lost yield at spacing 30 cm and greater, while the least sensitive (some taller vigorous semidwarf cultivars) tolerated spacing up to at least 50cm without yield loss. Yield sensitivity to wide spacing was unaffected by density but varied between years, being less in favourable cooler years, and was markedly greater with later plantings (Jan.). The response to yield on narrow raised beds (2–3 rows per bed, 75–90 cm between bed centres), which have many agronomic advantages, could be explained by the aforementioned yield responses to spacing, in this case the furrow gap or distance between rows on adjacent beds being critical. Yield testing with a furrow gap of 44–50 cm appeared to select cultivars more suited to this system, but it wasn't clear whether such cultivars represented the best option under normal 20 cm row spacing in the absence of raised beds. When testing was extended to very low plant densities, yield was remarkably insensitive (maximum yield often achieved with only 16/m2), provided the planting date was normal and the planting arrangement did not deviate greatly from a square grid, with the honeycomb design giving an additional small yield advantage. These yield responses reflect the great plasticity in wheat imparted especially by tillering, and appear to be reasonably well explained by the notion that maximum yield requires close to full light interception no later than just before flag leaf emergence, being the onset of dry weight accumulation in growing spikes. Greater leaf greenness and probably higher radiation use efficiency with very low densities (and wide gaps), and associated delays in 50% flowering, may also assist in compensation for gaps. In contrast to much conventional wisdom, it is suggested that a worthwhile breeding objective would be selection for high per spaced-plant yield, with a view to achieving normal (or better) commercial yields at very low plant densities (< 20/m2), thereby opening up opportunities for new breeding and agronomic strategies in this era of precision cropping. [ABSTRACT FROM AUTHOR]

Highlights • There is no unified rate of N fertilizer application for potatoes. • There is a quantitative link between the content of nitrate N in soil and potato productivity. • The maximum possible potato yield can be achieved by leveling the nitrate N to 22 mg/kg of soil. Abstract Potato has a good taste, and potato tubers contain mineral compounds and essential vitamins. Potato tuber yield is strongly influenced by N applications. The purpose of this paper is to present the 2015/2017 trial results on the effect of N nutrition and N fertilizers on potato productivity and quality, investigated on dark chestnut heavy loamy soils of Central Kazakhstan. Trials were conducted on irrigated soils high in phosphorus and potassium. These settings allowed revealing the exact role of N in potato nutrition and productivity. Results indicate that fertilizer application efficiency depends on how much nitrate N was there in soil before the application. In 2015, for example, the highest extra yields were achieved by applying 90 kg N/ha into soil containing 9.4 mg of nitrate-N in its 0–40 cm layer, while in 2016 and 2017, application rate was 60 kg N/ha and higher, considering that nitrate N amounted to 16–18 mg. There is a quantitative link between the content of nitrate N in soil and potato productivity. This link allows detecting when N is deficient, and measuring such fertilizer quantity that will give the maximum yield possible. Trials have shown that a uniform dose of N fertilizers that would guarantee best in all cases is non-existent. The maximum possible potato yield can be achieved by leveling the nitrate N in the soil to the lower optimum, which is 22 mg/kg of soil. [ABSTRACT FROM AUTHOR]

Highlights • We offered for the first time a comparison of Fruiting Efficiency (FE) across wheat, rye, barley, oats and triticale. • There were large differences within and across cereals in FE. • Interspecific differences implied a trade off with both inflorescence dry weight at anthesis and final grain weight. • Intraspecific differences were not compensated by opposite changes in inflorescence weight at anthesis and grain weight. Abstract Grain number (GN) is critical for yield determination, and understanding its physiology may be instrumental to further improving yield. Studying similarities and differences in yield physiology among cereals may highlight physiological traits that might become critical for understanding some constitutive differences between them. Recently it has been proposed that fruiting efficiency (FE, grains set per unit of inflorescence dry weight at anthesis IDWa) would be a relevant trait to further increase GN. In this research we report for the first time a comparison of GN determination due to IDWa and/or FE between five winter cereals crops (wheat, rye, barley, oats and triticale), analysing likely physiological bases for them and possible trade-offs. First, we performed a literature search and found a small number of papers on FE, mostly in wheat with limited data available for barley and triticale and nothing on oats and rye. Then, we conducted four experiments in which treatments consisted of the five small-grained cereal crops; in two of the experiments genotypes were combined with two levels of soil nitrogen availability. In triticale and barley the relationships between GN and either IDWa or FE were not significant implying that in these two cereals the environmental conditions affected in some cases one, while in other cases the other, physiological determinant of grain number. In wheat and rye, however, the relationships were clearer (and more significant) with FE than with SDWa, while for oats it was the other way around. Triticale and wheat showed the lowest FE values, rye exhibited the highest, and barley and oats were intermediate. When compared across cereals, FE was negatively related to the average spike- or panicle-DWa, indicating a trade-off in interspecific determination of GN. No relationship was found between FE and grain set percentage: differences in FE were mainly due to variation in the efficiency of setting fertile florets during pre-flowering inflorescence growth. The results also evidenced that this efficiency for setting fertile florets was related to the proportion of inflorescence resources partitioned to the growth of floret primordia. We observed no trade-off between FE and grain weight within each of the species, but an overall negative relationship when comparing across cereals (the latter likely explaining constitutive differences in grain weight among species). Therefore, it seemed that manipulations of FE within each of the species would not necessarily bring about compensations through reductions in grain weight and that to further increase fruiting efficiency cereal breeders may benefit from identifying prospect parents with an allocation of resources away from structural parts of the spikelets in favour of survival of labile florets. [ABSTRACT FROM AUTHOR]

Highlights • Yield correlated with five senescence traits from NDVI-time curves. • No correlation for yield between environments in 5 out of 6 comparisons (broad sense heritability = 0.39). • All senescence traits correlated negatively with concentration of water soluble carbohydrates at anthesis. • Water soluble carbohydrates correlated between environments in 6 out of 6 comparisons (broad sense heritability = 0.89). • Selection for low concentration of WSC could improve yield by improving both grain number per m2 and leaf area duration. Abstract High throughput phenotyping of canopy senescence based on Normalized Difference Vegetation Index (NDVI) could be useful in plant breeding. The aim of this paper was to assess the association between grain yield and canopy senescence quantified with NDVI in oat lines selected for grain yield and milling quality. Sixteen lines were grown in four winter-rainfall environments where logistic curves between NDVI and thermal time from anthesis (GS60) were fitted to return five traits: maximum NDVI, NDVImax ; minimum NDVI, NDVImin ; thermal time to 50% senescence, x50; rate of senescence, rate; and the area under the NDVI curve, area. Across sources of variation, residuals of yield after removing the effect of phenology correlated with area (r = 0.69), NDVImax (r = 0.67), x50 (r = 0.57), NDVImin (r = 0.51) and rate (r = −0.30), all significant at P < 0.05. All five senescence traits correlated negatively with concentration of water soluble carbohydrates at anthesis, particularly area (r = −0.75, P < 0.0001). There was no correlation for yield between environments in 5 out of 6 comparisons (broad sense heritability = 0.39) and water soluble carbohydrates correlated between environments in 6 out of 6 comparisons (broad sense heritability = 0.89). Correlations between environments were irregular for senescence traits. Selection for low concentration of water soluble carbohydrates could increase oat grain yield by improving both grain number per m2 and leaf area duration. [ABSTRACT FROM AUTHOR]

Abstract: Ecophysiological models are widely used to forecast potential impacts of climate change on future agricultural productivity and to examine options for adaptation by local stakeholders and policy makers. However, protocols followed in such assessments vary to such an extent that they constrain cross-study syntheses and increase the potential for bias in projected impacts. We reviewed 221 peer-reviewed papers that used crop simulation models to examine diverse aspects of how climate change might affect agricultural systems. Six subject areas were examined: target crops and regions; the crop model(s) used and their characteristics; sources and application of data on [CO2] and climate; impact parameters evaluated; assessment of variability or risk; and adaptation strategies. Wheat, maize, soybean and rice were considered in approximately 170 papers. The USA (55 papers) and Europe (64 papers) were the dominant regions studied. The most frequent approach used to simulate response to CO2 involved adjusting daily radiation use efficiency (RUE) and transpiration, precluding consideration of the interacting effects of CO2, stomatal conductance and canopy temperature, which are expected to exacerbate effects of global warming. The assumed baseline [CO2] typically corresponded to conditions 10–30 years earlier than the date the paper was accepted, exaggerating the relative impacts of increased [CO2]. Due in part to the diverse scenarios for increases in greenhouse gas emissions, assumed future [CO2] also varied greatly, further complicating comparisons among studies. Papers considering adaptation predominantly examined changes in planting dates and cultivars; only 20 papers tested different tillage practices or crop rotations. Risk was quantified in over half the papers, mainly in relation to variability in yield or effects of water deficits, but the limited consideration of other factors affecting risk beside climate change per se suggests that impacts of climate change were overestimated relative to background variability. A coordinated crop, climate and soil data resource would allow researchers to focus on underlying science. More extensive model intercomparison, facilitated by modular software, should strengthen the biological realism of predictions and clarify the limits of our ability to forecast agricultural impacts of climate change on crop production and associated food security as well as to evaluate potential for adaptation. [Copyright &y& Elsevier]

Highlights • Genetic gain of durum wheat in Spain slowed after the green revolution until reach a plateau in the last decade. • However, genetic gain was positively related with the mean and maximum daily temperatures of the testing sites. • The genetic advance was related to improvement in kernels m−2 and kernels spike−1. Abstract This paper addresses the question of whether there has been any genetic gain in yield for durum wheat released in Spain after the Green Revolution and assesses the agronomical and physiological traits associated with evolution of the crop during this time. Field experiments were carried out with a wide range of durum wheat cultivars (released in Spain from 1980 to 2009) and were conducted in different sites embracing a wide range of growing temperatures and water regimes at Aranjuez and Zamadueñas during three consecutive growing seasons (2013/14, 2014/15, 2015/16) under rainfed and supplemental irrigation and at Coria for two consecutive seasons (2014/15 and 2015/16) under rainfed conditions alone. Grain yield increased with the year of release of cultivars at a rate of 24 kg ha−1 y−1 (0.44% y−1) from 1980 to 2003, with no clear additional improvements thereafter. The moderate grain yield improvement from 1980 and 2003 was associated with kernels m−2 and kernels spike−1, with an increase of 117 kernels m−2 y−1 and 0.24 kernels spike−1 y−1, respectively. Moreover, aerial biomass at harvest and grain nitrogen yield increased with the year of release of cultivars for the entire period. However, no differences were found for thousand kernel weight, number of spikes m−2, days to heading, plant height, harvest index, canopy temperature depression, carbon isotope discrimination or grain nitrogen concentration. Overall, these results indicated that the rate of genetic progress in the yield of durum wheat in Spain after the Green Revolution has been low and has even stopped during the last decade, while no clear trend in some grain quality traits (TKW and grain N concentration) was recorded. However, the absolute and relative genetic gains estimated for yield were positively associated with the average mean and maximum daily temperatures from sowing to harvest of the testing site, which suggest that breeding has been performed under high-temperature environments. [ABSTRACT FROM AUTHOR]

Abstract: Even though planting cotton early in the season is advantageous, the cold sensitivity of cotton seedlings and low germination rates, especially in the areas experiencing low temperatures, are the main obstacle for the early seasonal planting. A total of 106 genotypes from three different species; Gossypium hirsutum L., G. barbadense L., and G. herbaceum L. were screened for cold tolerance using three different approaches. Furthermore, the best screening method to differentiate between the genotypes for cold tolerance, and to predict their field emergence rates was also determined. In detail, optimal germination percentages were measured at 30°C with the results ranging from 61% to 99%. On the other hand, cold temperature germination rates and emergence percentages ranged from 8% to 82% in paper test and from 8% to 88% (the 7th day after planting) in sand test at 18°C, and field emergence percentages ranged from 44% to 77% at 28 days after planting. A significant difference between cotton species in terms of their tolerance to cold was observed. That is, G. barbadense genotypes had higher germination rates than the other two species in the three methods used. There was no correlation between optimal germination rates and field emergence percentages. Among cold temperature germination methods, the 18°C paper test was better in predicting of field emergence percentage, in differentiating between genotypes in terms of their cold tolerance and in determining seed vigor. G. hirsutum cultivars; 8106-2, AYDIN-110, CORINA, DP-388, DPL-50, DPL-5614, NAZILLI-342 and one G. barbadense cultivar, GIZA 70 were more cold tolerant among all the cotton cultivars screened in this study. [ABSTRACT FROM AUTHOR]

Abstract: Dynamic crop models are frequently used in ecology, agronomy and environmental sciences for simulating crop and environmental variables at a discrete time step. They often include a large number of parameters whose values are uncertain, and it is often impossible to estimate all these parameters accurately. A common practice consists in selecting a subset of parameters by global sensitivity analysis, estimating the selected parameters from data, and setting the others to some nominal values. For a discrete-time model, global sensitivity analyses can be applied sequentially at each simulation date. In the case of dynamic crop models, simulations are usually computed at a daily time step and the sequential implementation of global sensitivity analysis at each simulation date can result in several hundreds of sensitivity indices, with one index per parameter per simulation date. It is not easy to identify the most important parameters based on such a large number of values. In this paper, an alternative method called multivariate global sensitivity analysis was investigated. More precisely, the purposes of this paper are (i) to compare the sensitivity indices and associated parameter rankings computed by the sequential and the multivariate global sensitivity analyses, (ii) to assess the value of multivariate sensitivity analysis for selecting the model parameters to estimate from data. Sequential and multivariate sensitivity analyses were compared by using two dynamic models: a model simulating wheat biomass named WWDM and a model simulating N2O gaseous emission in crop fields named CERES-EGC. N2O measurements collected in several experimental plots were used to evaluate how parameter selection based on multivariate sensitivity analysis can improve the CERES-EGC predictions. The results showed that sequential and multivariate sensitivity analyses provide modellers with different types of information for models which exhibit a high variability of sensitivity index values over time. Conversely, when the parameter influence is quite constant over time, the two methods give more similar results. The results also showed that the estimation of the parameters with the highest sensitivity indices led to a strong reduction of the prediction errors of the model CERES-EGC. [Copyright &y& Elsevier]

Abstract: Specification effects in terms of how technology options are contrasted can introduce bias in impact assessment. In a companion paper we evaluated the on-farm impacts of zero tillage (ZT) wheat as a resource-conserving technology in the rice–wheat systems of India''s Haryana State and Pakistan''s Punjab province [Erenstein, O., Farooq, U., Malik, R.K., Sharif, M., 2008. On-farm impacts of zero tillage wheat in South Asia''s rice–wheat systems. Field Crop Res. 105, 240–252]. The underlying field work surveyed plots of full adopters (only ZT plots), partial adopters (ZT and conventional tillage [CT] plots on same farm) and non-adopters (only CT plots). The companion paper assumes that the comparison between the ZT plots of full plus partial adopters and CT plots of partial adopters is the least-biased assessment of ZT''s on-farm impact. Here we revisit this underlying assumption and draw on complementary farm survey findings to illustrate the extent of specification effects in the assessment of on-farm impacts of ZT wheat in the same study areas. The study thereby distinguishes between three contrasts between ZT and CT within the same dataset: (1) plain contrast (all plots of adopters and non-adopters); (2) adopter-only contrast (full and partial adopters only, as used in Erenstein et al. [Erenstein, O., Farooq, U., Malik, R.K., Sharif, M., 2008. On-farm impacts of zero tillage wheat in South Asia''s rice–wheat systems. Field Crop Res. 105, 240–252]); (3) pair-wise contrast (partial adopters only). Proceeding from type 1 to type 3 comparisons the number of observations decrease but this is compensated by an increasing ability to control for variation. The ability of type 3 comparisons to pick up relatively small but significant differences is an important consideration in farm survey impact assessment. However, there is also an increase in partial adoption bias and further follow-up studies are needed to understand the implications of this. The comparisons show that the ZT effects on savings for diesel, tractor time and cost for wheat cultivation are particularly robust. In Haryana ZT''s positive implications for yield and the other financial indicators were also statistically robust, but in Punjab these were sensitive to specification effects. Particularly sensitive to specification effects were the ZT effects on the productivity of applied water in both sites. [Copyright &y& Elsevier]

Abstract: This paper is the first of a series that investigates whether new cropping systems with permanent raised beds (PRBs) or Flat land could be successfully used to increase farmers’ incomes from rainfed crops in Lombok in Eastern Indonesia. This paper discusses the rice phase of the cropping system. Low grain yields of dry-seeded rice (Oryza sativa) grown on Flat land on Vertisols in the rainfed region of southern Lombok, Eastern Indonesia, are probably mainly due to (a) erratic rainfall (870–1220mm/yr), with water often limiting at sensitive growth stages, (b) consistently high temperatures (average maximum=31°C), and (c) low solar radiation. Farmers are therefore poor, and labour is hard and costly, as all operations are manual. Two replicated field experiments were run at Wakan (annual rainfall=868mm) and Kawo (1215mm) for 3 years (2001/2002 to 2003/2004) on Vertisols in southern Lombok. Dry-seeded rice was grown in 4 treatments with or without manual tillage on (a) PRBs, 1.2m wide, 200mm high, separated by furrows 300mm wide, 200mm deep, with no rice sown in the well-graded furrows, and (b) well-graded Flat land. Excess surface water was harvested from each treatment and used for irrigation after the vegetative stage of the rice. All operations were manual. There were no differences between treatments in grain yield of rice (mean grain yield=681g/m2) which could be partly explained by total number of tillers/hill and mean panicle length, but not number of productive tillers/hill, plant height or weight of 1000 grains. When the data from both treatments on PRBs and from both treatments on Flat land, each year at each site were analysed, there were also no differences in grain yield of rice (g/m2). When rainfall in the wet season up to harvest was over 1000mm (Year 2; Wakan, Kawo), or plants were water-stressed during crop establishment (Year 1; Wakan) or during grain-fill (Year 3: Kawo), there were significant differences in grain yield (g/1.5m2) between treatments; generally the grain yield (g/1.5m2) on PRBs with or without tillage was less than that on Flat land with or without tillage. However, when the data from both treatments on PRBs and from both treatments on Flat land, each year at each site, were analysed, the greater grain yield of dry-seeded rice on Flat land (mean yield 1 092g/1.5m2) than that on PRBs (mean 815g/1.5m2) was mainly because there were 25% more plants on Flat land. Overall when the data in the 2 outer rows and the 2 inner rows on PRBs were each combined, there was a higher number of productive tillers in the combined outer rows (mean 20.7tillers/hill) compared with that in the combined inner rows on each PRB (mean 18.2tillers/hill). However, there were no differences in grain yield between combined rows (mean 142g/m row). Hence with a gap of 500mm (the distance between the outer rows of plants on adjacent raised beds), plants did not compensate in grain yield for missing plants in furrows. This suggests that rice (a) also sown in furrows, or (b) sown in 7 rows with narrower row-spacing, or (c) sown in 6 rows with slightly wider row-spacing, and narrower gap between outer rows on adjacent beds, may further increase grain yield (g/1.5m2) in this system of PRBs. The growth and the grain yield (y in g/m2) of rainfed rice (with rainfall on-site the only source of water for irrigation) depended mainly on the rainfall (x in mm) in the wet season up to harvest (due either to site or year) with y =1.1x −308; r 2 =0.54; p <0.005. However, 280mm (i.e. 32%) of the rainfall was not directly used to produce grain (i.e. when y =0g/m2). Manual tillage did not affect growth and grain yield of rice (g/m2; g/1.5m2), either on PRB or on Flat land. [Copyright &y& Elsevier]

Abstract: In Western Australia, farmer-led farming systems groups (grower groups) are actively forming partnerships with other grower groups, researchers and private industry. As the broadacre grain and livestock farming system increases in complexity, existing partnerships may not be adequate and a new approach is needed. An organisational form that is designed to work in such complexity is the ‘network’. Grower group networks are able to create an environment where shared understanding and/or collective action is used to achieve outcomes where there are no readily available solutions. In 2002, the Grower Group Network project was established to support grower groups in a network to provide their members with access to the latest information and research. The organisation of farming systems groups into networks has made them more accessible and relevant to researchers. In this paper, a description of the role of grower groups and grower group networks can play in research projects is outlined, illustrated by case studies of successful partnerships. The most successful projects occur when farming systems groups and research providers develop and implement a new project together. Grower group networks are also a very effective means of delivering research outcomes as they can provide researchers with opportunities for impact well beyond partnerships with one or two grower groups. The paper concludes with a description of the future challenges for grower group networks. [Copyright &y& Elsevier]

Abstract: The paper investigates management and cultivar type effects on pearl millet stover yield and fodder quality. Sixteen pearl millet cultivars available to farmers in India were selected to represent three cultivar types: (1) traditional landrace germplasm from the arid/semi-arid millet production zones, (2) improved dual-purpose (grain and stover) open-pollinated varieties incorporating differing amounts of traditional landrace germplasm and (3) commercial, grain-type F1 hybrids, bred for use in the arid/semi-arid zone. The cultivars were grown for 2 years (2000 and 2001) at high fertility (HF: 65kgNha−1 and 18kgPha−1) and low fertility (LF: 21kgNha−1 and 9kgPha−1). Within each fertility level high (HP) and low (LP) plant population densities were established by varying sowing rate and then thinning to the target populations (HP: 11plantsm−2 and LP: 5plantsm−2). Stover fodder quality traits (nitrogen concentration, sugar content, in vitro digestibility and metabolizable energy content) were analyzed using a combination of conventional laboratory analysis and near infrared spectroscopy. In general, fertility level and cultivar type had strong effects on grain and stover yields, and on a range of stover nutritional quality traits, but with significant year interactions. In contrast, the effect of population density on these variables was largely insignificant. Higher fertilizer application significantly increased grain and stover yields and stover nitrogen concentration, in vitro digestibility and metabolizable energy content. As a result, fertilization resulted in significant increases in the yields of both digestible and metabolizable stover. Landrace cultivars as a group produced higher quality fodder than modern hybrids, but at a significant cost in grain yield. Dual-purpose, open-pollinated cultivars were generally intermediate between the landraces and hybrids, in terms of both stover quality and grain yield, but produced the highest yields of both digestible and metabolizable stover. The paper discusses the implications of these findings for Indian pearl millet farmers with various resource levels and farming objectives. [Copyright &y& Elsevier]

Abstract: Field experiments with soybean demonstrated that the extension of photoperiod after flowering increases both the duration of the post-flowering phase and the production of seeds. These results suggest that cultivars with increased duration of the post-flowering phase could be selected to improve soybean yields. The aims of this paper were to: (a) evaluate the ability of the CROPGRO-soybean model to reproduce the experimental relationships between seed number and duration of the critical phase between first and last pod, and (b) assess the putative benefits and trade-offs of variable durations of the critical phase in a south–north transect in the Pampas of Argentina. We varied the genetic coefficients accounting for photothermal requirements and photoperiod sensitivity of soybean A5409-RG (maturity group V), reducing pre-flowering phase while maintaining time to maturity. The model produced sound estimates of crop phenology and reproduced the positive relationship between seed production and the duration of the critical period between first and last pod found in field studies. Linking the model with long-term climate records for six locations between 31 and 37°S, indicated that substantial yield gains could result from increasing the relative duration of post-flowering phases. A hypothetical cultivar with flowering time typical of cultivars of maturity group III and total cycle typical of cultivars of group V, outyielded the traditional cultivar of group V in most cases. For well-watered crops, extension of the critical period had a positive effect in yield in all seasons and locations, whereas for rainfed crops, the extension of the critical period increased yield in 95% of the simulated scenarios. The magnitude of the effect was strongly asymmetric: yield gains were up to 1Mgha−1 whereas losses were below 0.2Mgha−1. The modelled results in this paper indicate that shortening pre-flowering period without changing the duration of the whole cycle should increase yields in a broad range of latitudes and environmental conditions. [Copyright &y& Elsevier]

Abstract: Whereas the concept that availability of resources drives seed production is sound in principle, it is incomplete as there are many solutions to the allocation of resources that derive from the trade-off between number and size. This paper examines evolutionary aspects of this trade-off in annual grain crops. The analysis is centred on the working hypotheses that, for a given species and environment, allocation of resources to reproduction involves (H1) high plasticity in seed number, which allows for variable resource availability, and (H2) a relatively narrow range of seed size that results from evolutionary and agronomic selection. Comparisons between crops and fish are used to highlight common evolutionary elements in taxa where parents provide little or no care to their offspring, with the consequence that both number and early survival of offspring, hence fitness of parents, are partially related to embryo size and reserves. The plasticity of seed number in relation to availability of resources is analysed against the established relationship between offspring number and parent growth rate during critical stages. The notion that seed size is under stabilising selection is analysed against three conditions: (1) mean seed size is conservative for a given species and environment, (2) seed size affects fitness, and (3) seed size is heritable. Databases from published papers were compiled to analyse the relative variability of seed size and number, and the heritability of seed size. Evidence for and against the link between seed size and parental fitness is revised using the Smith–Fretwell model as framework (Am. Nat., 108, 499–506). The proposal of high plasticity of seed number and narrow variability of seed size resulting from stabilising natural selection is generally consistent with evolutionary and genetic considerations. Agronomic selection may have reinforced natural selection leading to relatively narrow seed size in species such as wheat and soybean, where cultivated types retained high plasticity for seed number. In contrast, selection for one or few inflorescences in crops like sunflower and maize may have morphologically reduced seed number plasticity and increased variability of seed size and its responsiveness to resource availability in relation to their wild ancestors. [Copyright &y& Elsevier]

Abstract: The critical crop nitrogen uptake is defined as the minimum nitrogen uptake necessary to achieve maximum biomass accumulation (W). Across a range of crops, the critical N uptake is related to W by a power function with a coefficient less than unity that suggests crop N uptake is co-regulated by both soil N supply and biomass accumulation. However, crop N demand is also often linearly related to the expansion of the leaf area index (LAI) during the vegetative growth period. This suggests that crop N demand could be also linked with LAI extension. In this paper, we develop theory to combine these two concepts within a common framework. The aim of this paper is to determine whether generic relationships between N uptake, biomass accumulation, and LAI expansion could be identified that would be robust across both species and environment types. To that end, we used the framework to analyze data on a range of species, including C3 and C4 ones and mono- and di-cotyledonous crops. All crops were grown in either temperate or tropical and subtropical environments without limitations on N supply. The relationship between N uptake and biomass was more robust, across environment types, than the relationship of LAI with biomass. In general, C3 species had a higher N uptake per unit biomass than C4 species, whereas dicotyledonous species tended to have higher LAI per unit biomass than monocotyledonous ones. Species differences in N uptake per unit biomass were partly associated with differences in LAI and N-partitioning. Consequently the critical leaf-N uptake per unit LAI (specific leaf nitrogen, SLN) was relatively constant across species at 1.8–2.0gm−2, a value that was close to published data on the critical SLN of new leaves at the top of the canopy. Our results indicate that critical N uptake curves as a function of biomass accumulation may provide a robust platform for simulating N uptake of a species. However, if crop simulation models are to capture the genotypic and environmental control of crop N dynamics in a physiologically functional manner, plant growth has to be considered as the sum of a metabolic (e.g. leaves) and a structural (e.g. stems) compartment, each with its own demand for metabolic and structural N. [Copyright &y& Elsevier]