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Food security and the agricultural economy are both dependent on the temporal stability of crop yields. To this end, increasing crop diversity has been suggested as a means to stabilize agricultural yields amidst an ongoing decrease in cropping system diversity across the world. Although diversity confers stability in many natural ecosystems, in agricultural systems the relationship between crop diversity and yield stability is not yet well resolved across spatial scales. Here, we leveraged crop area, production, and price data from 1981 to 2020 to assess the relationship between crop diversity and the stability of both economic and caloric yields at the state level within the USA. We found that, after controlling for climatic instability and differences in irrigated area, crop diversity was positively associated with economic yield stability but negatively associated with caloric yield stability. Further, we found that crops with a propensity for increasing economic yield stability but reducing caloric yield stability were often found in the most diverse states. We propose that price responses to changes in production for high-value crops underly the positive relationship between diversity and economic yield stability. In contrast, spatial concentration of calorie-dense crops in low-diversity states contributes to the negative relationship between diversity and caloric yield stability. Our results suggest that the relationship between crop diversity and yield stability is not universal, but instead dependent on the spatial scale in question and the stability metric of interest.

In Cambodia, rice is predominantly produced in areas with rainfed lowland conditions where photoperiod-sensitive varieties are cultivated. A number of varieties have been released for rainfed lowland areas, and the rice grain yield has reportedly increased by approximately 12% over the past ten years. Moreover, great fluctuations in yield performance have been observed across different soil types of the rainfed ecosystems of Cambodia. Therefore, the present study aimed to analyze the grain yield and stability among ten popular varieties that were released for rainfed lowland ecosystems across the four different soil types in Cambodia in two years. The grain yield varied 566 g m−2 as the highest in clay soil and about 220 g m−2 as the lowest in sandy soil. A combined ANOVA revealed significant differences for the main effect of genotype, environment, and genotype-by-environment interaction (GEI) for all yield-related traits and grain yield per square meter. The principal component test results showed that the heterogeneity of grain yield was mainly attributable to the effect of environment, followed by the effect of genotype. In fertile conditions, a higher percentage of filled grains was supported by higher leaf N until the late stage with a wider flag leaf. In conditions of moderate fertility, larger numbers of panicles were supported by a higher percentage of productive culms with higher leaf N until the late stage. In conditions of poor fertility, a higher percentage of filled grains was supported by higher leaf N until the late stage, which is considered to be important for higher grain yield. The variety Phka Rumduol showed these preferable traits and produced higher yields in fertile to poor natural soil fertility conditions with moderate variation. This variety is considered to be more desirable and ideal due to its stability and higher grain yield. The other varieties, namely, Phka Mealdei, Phka Rumdeng, and CAR4, were identified as above-average yielders. Therefore, those varieties potentially may be recommended for cultivation in rainfed lowland rice ecosystems in Cambodia due to their high yields. CAR4 showed moderate variation at the same level as Phka Rumduol. From the point of stability, Phka Rumduol and CAR4 can be expected to excel.

【Objective】Water scarcity and inefficient irrigation are major constraints in paddy rice production, particularly in regions cultivating double-season rice. This paper experimentally investigates the effects of long-term controlled water irrigation on the yield and stability of double-season rice.【Method】The experiment was conducted in a double-season rice field from 2013 to 2019 in Jingzhou City, Hubei Province. There were two irrigation treatments: conventional irrigation (CK) and controlled water irrigation (WI). In each treatment, we measured yield and yield component, biomass, and yield stability indices characterized by the coefficient of variation (CV) and the sustainability yield index (SYI).【Result】Compared with conventional irrigation, controlled irrigation only changed the biomass of early rice by -3.87% to 6.12%, the effective spike numbers by -8.56% to 2.32%, the seed-setting rate by -4.67% to 1.03%, the grain numbers per spike by -9.95% to 5.99%, the 1000-grain weight by -3.54% to -0.54%, the grain yield by -6.69% to 6.70%, and the harvest index by -3.11% to 0.56%. For late rice, controlled irrigation increased the biomass by 0.57%-13.95%, changed the effective spike numbers by -0.21% to 7.46%, seed-setting rate by -1.44% to 8.12%, the grain numbers per spike by -14.12% to 7.08%, the 1 000-grain weight by -0.11% to 2.97%, the grain yield by -0.88% to 9.70%, and the harvest index by -3.72% to 1.97%. Overall, controlled irrigation increased the total yield of double-season rice by 1.07%-7.73%. In addition, controlled irrigation increased the CV of early rice by 10.28% and reduced its SYI by 0.756, while showing no significant effect on late rice. Overall, controlled irrigation did not show a noticeable impact on the yield stability of double-season rice, with the CV of total yield decreasing from 4.83% to 3.79%. Partial least squares path modelling showed that controlled irrigation affected early rice yield negatively and late rice yield positively. Meteorological factors, such as average temperature and rainfall, significantly impacted both yield and biomass of the rice.【Conclusion】Controlled irrigation reduces early rice yield but increases late rice yield. This complementary effect maintains the yield stability of double-season rice. Controlled irrigation is thus a water-saving strategy to sustain paddy fields.

Cultivar mixtures have been proposed as a way to increase diversity and thereby improve plant production, but our understanding of the effects of mixing cultivars on crop diseases and resource-use efficiency remains fragmentary. We performed a meta-analysis to assess the effects of cultivar mixtures on crop yield, yield stability, resource-use efficiency, and disease severity compared with monocultures of twelve major crops. We found that, overall, mixing of cultivars increased crop yield by 3.82%. Yield gains from mixing cultivars were highest in rice (+16.1%), followed by maize (+8.5%), and were lowest in barley (+0.9%) and sorghum (no increase). Temporal yield stability increased with the number of cultivars in the mixtures. Overall, mixing cultivars increased crop biomass, leaf area index, photosynthetic rate, and Water-use efficiency by 5.1, 7.2, 8.5 and 4.3%, respectively, and decreased disease incidence by 24.1%. Cultivar mixtures were more effective in mitigating diseases and increasing yields in studies performed at lower latitudes, higher mean annual temperatures, and higher mean annual precipitation. Our study complements and adds to previous research, indicating that cultivar mixtures reduce crop losses to disease and enhance resource-use efficiency compared with monocultures globally. We conclude that the targeted use of cultivar mixtures with appropriate management practices can reduce resource and pesticide inputs while maintaining high yields, thereby promoting sustainable and productive agriculture. Graphical abstract

Drought stress during reproductive development could drastically reduce wheat grain number and yield, but quantitative evaluation of such an effect is unknown under climate change. The objectives of this study were to evaluate potential yield benefits of drought tolerance during reproductive development for wheat ideotypes under climate change in Europe, and to identify potential cultivar parameters for improvement. We used the Sirius wheat model to optimize drought-tolerant (DT) and drought-sensitive (DS) wheat ideotypes under a future 2050 climate scenario at 13 contrasting sites, representing major wheat growing regions in Europe. Averaged over the sites, DT ideotypes achieved 13.4% greater yield compared with DS, with higher yield stability. However, the performances of the ideotypes were site dependent. Mean yield of DT was 28–37% greater compared with DS in southern Europe. In contrast, no yield difference (≤1%) between ideotypes was found in north-western Europe. An intermediate yield benefit of 10–23% was found due to drought tolerance in central and eastern Europe. We conclude that tolerance to drought stress during reproductive development is important for high yield potentials and greater yield stability of wheat under climate change in Europe.

Barley is the fourth largest grain crop globally with varieties suited to temperate, subarctic, and subtropical areas. The identification and subsequent selection of superior varieties are complicated by genotype-by-environment interactions. The main objective of this study was to use parametric and non-parametric stability measures along with a GGE biplot model to identify high-yielding stable barley genotypes in Iran. Eighteen barley genotypes (16 new genotypes and two control varieties) were evaluated in a randomized complete block design with four replications at five locations over three growing seasons (2013–2014, 2014–2015, 2015–2016). The combined analysis of variance indicated that the environment main effect accounted for > 69% of all variation, compared with < 31% for the combined genotype (G) and genotype-by-environment interaction effects. The mean grain yield of each genotype across the five test sites and three seasons ranged from 1900 to 2302 kg ha−1. Using Spearman’s rank correlation and principal component analyses, the stability measures were divided into three groups: the first included mean yield, TOP and b, which are related to the dynamic concept of stability, the second comprised θi, Wi2, σi2, CVi, \\[S_di^2\\], KR, and the non-parametric measures, S(i) and NP(i), which are related to the static concept of stability, and the third included θi and R2. The GGE biplot analysis indicated that, of the five test locations, Gonbad and Moghan had the most discriminating and representative environments. Hence, these locations are recommended as ideal test locations in Iran for the selection of superior genotypes. The numerical and graphical methods both produced similar results, identifying genotypes G12, G13, and G17 as the best material for rainfed conditions in Iran; these genotypes should be promoted for commercial production.

Background and aims Crop diversity has been repeatedly shown to support multiple ecosystem functions, both directly and indirectly, driven by interspecific root-root interactions. Despite continuous advances in this field, some research gaps remain, and we need to pay more attention to the design and management of multi-species and multi-cultivar systems in the future. Scope We review advances in intercropping in enhanced ecosystem functioning in competition-based and facilitation-based intercropping systems via root-root interactions. We also consider recent achievements in yield stability and soil fertility. We address several perspectives to focus on towards more sustainable agriculture via intercropping or cultivar mixtures in the future. Conclusions In competition-based systems, scramble competition via root-root competition and contest competition involving allelochemicals offset yield advantages of target crop species. However, niche differentiation and selection of desirable crop combinations to minimize negative effects through secondary metabolites may also help to gain yield advantages in intercropping and cultivar mixtures. In facilitation-based systems, selecting genotypes of facilitated species with root traits that best match the facilitator may strengthen the facilitative interactions in resource enrichment and disease and pest control. We need more long-term research to explore the effects of belowground processes on soil fertility, ecosystem stability, adaptation, and mitigation of climate change to establish sustainable agroecosystems in the future. It is also urgent to develop new methods to link belowground processes to functioning in multi-species and multi-cultivar agroecosystems.

KEY MESSAGE : Analyses of registration trials of winter barley suggested that yield and yield stability can be enhanced by developing hybrid instead of line varieties. Yield stability is central to cope with the expected increased frequency of extreme weather conditions. The objectives of our study were to (1) examine the dimensioning of field trials needed to precisely portray yield stability of individual winter barley (Hordeum vulgare L.) genotypes, (2) compare grain yield performance and yield stability of two-rowed lines with those of six-rowed lines and hybrids, and (3) investigate the association of various agronomic traits with yield stability. Static and dynamic yield stability as well as grain yield performance was determined in five series of 3-year registration trials of winter barley in Germany. Each series included 4 or 5 six-rowed hybrids, 40–46 six-rowed inbred lines, as well as 42–49 two-rowed inbred lines. The genotypes were evaluated in 10–45 environments, i.e. year-by-location combinations. We found that precise assessment of yield stability of individual genotypes requires phenotyping in at least 40 test environments. Therefore, selection for yield stability is not usually feasible since the required number of test environments exceeds the common capacity of barley breeding programs. Also, indirect improvement of yield stability by means of agronomic traits seemed not possible since there was no constant association of any agronomic trait with yield stability. We found that compared with line varieties, hybrids showed on average higher grain yield performance combined with high dynamic yield stability. In conclusion, breeding hybrid instead of line varieties may be a promising way to develop high yielding and yield stable varieties.

Climate change affects the spatial and temporal distribution of crop yields, which can critically impair food security across scales. A number of previous studies have assessed the impact of climate change on mean crop yield and future food availability, but much less is known about potential future changes in interannual yield variability. Here, we evaluate future changes in relative interannual global wheat yield variability (the coefficient of variation (CV)) at 0.25° spatial resolution for two representative concentration pathways (RCP4.5 and RCP8.5). A multi-model ensemble of crop model emulators based on global process-based models is used to evaluate responses to changes in temperature, precipitation, and CO2. The results indicate that over 60% of harvested areas could experience significant changes in interannual yield variability under a high-emission scenario by the end of the 21st century (2066–2095). About 31% and 44% of harvested areas are projected to undergo significant reductions of relative yield variability under RCP4.5 and RCP8.5, respectively. In turn, wheat yield is projected to become more unstable across 23% (RCP4.5) and 18% (RCP8.5) of global harvested areas—mostly in hot or low fertilizer input regions, including some of the major breadbasket countries. The major driver of increasing yield CV change is the increase in yield standard deviation, whereas declining yield CV is mostly caused by stronger increases in mean yield than in the standard deviation. Changes in temperature are the dominant cause of change in wheat yield CVs, having a greater influence than changes in precipitation in 53% and 72% of global harvested areas by the end of the century under RCP4.5 and RCP8.5, respectively. This research highlights the potential challenges posed by increased yield variability and the need for tailored regional adaptation strategies.