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Maintaining or even increasing crop yields while reducing nitrous oxide (N2O) emissions is necessary to reconcile food security and climate change, while the metric of yield‐scaled N2O emission (i.e., N2O emissions per unit of crop yield) is at present poorly understood. Here we conducted a global meta‐analysis with more than 6000 observations to explore the variation patterns and controlling factors of yield‐scaled N2O emissions for maize, wheat and rice and associated potential mitigation options. Our results showed that the average yield‐scaled N2O emissions across all available data followed the order wheat (322 g N Mg−1, with the 95% confidence interval [CI]: 301–346) > maize (211 g N Mg−1, CI: 198–225) > rice (153 g N Mg−1, CI: 144–163). Yield‐scaled N2O emissions for individual crops were generally higher in tropical or subtropical zones than in temperate zones, and also showed a trend towards lower intensities from low to high latitudes. This global variation was better explained by climatic and edaphic factors than by N fertilizer management, while their combined effect predicted more than 70% of the variance. Furthermore, our analysis showed a significant decrease in yield‐scaled N2O emissions with increasing N use efficiency or in N2O emissions for production systems with cereal yields >10 Mg ha−1 (maize), 6.6 Mg ha−1 (wheat) or 6.8 Mg ha−1 (rice), respectively. This highlights that N use efficiency indicators can be used as valuable proxies for reconciling trade‐offs between crop production and N2O mitigation. For all three major staple crops, reducing N fertilization by up to 30%, optimizing the timing and placement of fertilizer application or using enhanced‐efficiency N fertilizers significantly reduced yield‐scaled N2O emissions at similar or even higher cereal yields. Our data‐driven assessment provides some key guidance for developing effective and targeted mitigation and adaptation strategies for the sustainable intensification of cereal production. [ABSTRACT FROM AUTHOR]

The plant microbiota fulfils various crucial functions related to host health, fitness, and productivity. Over the past years, the number of plant microbiome studies continued to steadily increase. Technological advancements not only allow us to produce constantly increasing datasets, but also to extract more information from them in order to advance our understanding of plant-microbe interactions. The growing knowledge base has an enormous potential to improve microbiome-based, sustainable agricultural practices, which are currently poorly understood and have yet to be further developed. Cereal plants are staple foods for a large proportion of the world's population and are therefore often implemented in microbiome studies. In the present review, we conducted extensive literature research to reflect the current state of knowledge in terms of the microbiome of the four most commonly cultivated cereal plants. We found that currently the majority of available studies are targeting the wheat microbiome, which is closely followed by studies on maize and rice. There is a substantial gap, in terms of published studies, addressing the barley microbiome. Overall, the focus of most microbiome studies on cereal plants is on the below-ground microbial communities, and there is more research on bacteria than on fungi and archaea. A meta-analysis conducted in the frame of this review highlights microbiome similarities across different cereal plants. Our review also provides an outlook on how the plant microbiota could be harnessed to improve sustainability of cereal crop production. [ABSTRACT FROM AUTHOR]

Food security can be under threat due to climate change, which has the potential to alter crop yield. Wheat, maize, and rice are major crops contributing to global food security. The impact of climate change on crop yield with different models and techniques has been projected; this article reviewed the worldwide impact of climate change on future wheat, rice, and maize production. Wheat and maize crop yields may increase due to climate change in colder regions and may decrease in the countries near the equator. The increase in carbon dioxide concentration in the atmosphere may help wheat and maize crops regarding increased carbon intake in colder regions. The rice crop yield may decrease in almost all major rice-producing countries due to water scarcity, which can be amplified due to climate change. The impact of climate change on crop yield prediction involves uncertainties due to different crop models, global circulation models, and bias correction techniques. It is recommended to use multiple climatic models and more than one bias correction technique for better climatic projections. Adaptation measures could help to reduce the adverse impacts of future climate on agriculture. Shifting the planting calendar, irrigation and nutrient management, improving crop varieties, and expanding the agricultural areas are suggested as the most effective adaptation actions in response to climate change. The findings of this study may help policymakers to achieve Sustainable Development Goal (SDG) 2 (Zero Hunger) and SDG 13 (Climate Action). [ABSTRACT FROM AUTHOR]

In Ethiopia, smallholder farmers are responsible for most food production. Though yield levels in grain crops have improved greatly over the years, they are still much lower than their potential. The source of yield improvements and the causes of those yield gaps are not well understood. To explain the drivers of yield gaps and current sources of yield improvements in four major cereals (teff, maize, wheat, and sorghum) and three grain legumes (faba bean, common bean, and soybean), we accessed the databases of the Global Yield Gap Atlas, the Food and Agriculture Organization of the United Nations, and the Central Statistical Agency of Ethiopia. Refereed journal articles and grey literature were sought in online databases using keywords. The results showed large increases in production of grain crops with little or no increase in areas of production. The yield increases were primarily attributed to genetic gain rather than agronomic improvements. Farmers' yields remain far lower than those from on-farm trials and on-station trials and the calculated water-limited yield potential. Currently, yields of wheat, maize, sorghum, and common bean in Ethiopia are about 26.8, 19.7, 29.3, and 35.5% of their water-limited yield potentials. Significant portions of the yield gaps stem from low adoption and use of improved varieties, low application of inputs, continual usage of un-optimized crop management practices, and uncontrolled biotic and abiotic stresses. Proper application of fertilizers and use of improved varieties increase yield by 2 to 3 fold and 24–160%, respectively. Cereal-legume intercropping and crop rotation practices increase yield while reducing severity of pests and the need for application of synthetic fertilizers. In contrast, abiotic stresses cause yield reductions of 20–100%. Hence, dissection of the water-limited yield gap in terms of technology, resource, and efficiency yield gaps will allow the prioritization of the most effective intervention areas. [ABSTRACT FROM AUTHOR]

The water footprint (WF), based on irrigation water quality, is important as a decision-making tool for crop selection based on the comparative advantage of water consumption and yield to maximize agricultural water productivity and sustainably improve water use efficiency. This paper presents a generic link between climate variability and water footprint. To support this link, a case study is presented for wheat and maize in different agro-climate zones in Egypt. In this study, the three agro-ecological zones, Nile Delta, Middle Egypt, and Upper Egypt, were selected to represent three different microclimates. The climate data were analyzed to estimate reference evapotranspiration (ETo) and calculate crop water use (CWU) for wheat and maize from 2015 through 2019. Cultivated area and yield data were analyzed during the study period. Water footprint (WF) was calculated for old land (clay soils) and new lands (sandy soils) in three climate regions based on blue and grey water. Green water was excluded due to negligible rainfall depths in Egypt. The results showed that the mean values of WF for maize were 1067, 1395, 1655 m3/ton in old land and 1395, 1634, 2232 m3/ton in new land under the three climate regions, respectively, while it was 923, 982, 1117 m3/ton in old land and 1180, 1258, 1452 m3/ton for wheat in new land for the three regions, respectively. The results show that the crop water use fluctuated over regions due to climate variability where the CWU values were 6211, 7335, 8007 m3/ha for maize and 4348, 4825, 5774 m3/ha for wheat in the three regions, respectively. The results show an 11% and 33% increase in maize and an 18% and 29% increase in wheat CWU in Middle and Upper Egypt regions comparing to what was observed in Nile Delta due to an increase in solar radiation, temperature, and wind speed. The Egypt mean value of wheat water footprint was 1152 m3/ton and mean value of maize water footprint was 1563 m3/ton. The data clearly show the effect of microclimate variability on WF and irrigation requirements between regions. The methodology and results from this study provide a pathway to help the policy makers to mitigate climate change impacts on crop yield and to enhance water resources management in major crop production regions by redistribution of the cropping patterns based on the comparative advantages of each crop within each region. The crop choices relative to the soil water retention characteristics could also contribute to the moderation of microclimate, which affects ETo and ETc and the water footprint. [ABSTRACT FROM AUTHOR]

Crop heat stress is a threat to food supply, with heatwaves expected to increase in frequency and intensity globally. In addition to yield loss, heat stress dramatically reduces fertility and seed-setting rate, grain quality and weight, and seed germination and growth. Genetic variability for heat stress tolerance can be used in breeding programs to develop tolerant genotypes. The availability of genome assemblies with high-confidence sequences for many cereal crops, including rice, maize, wheat and barley, now allows the identification of heat stress tolerance-associated genes and gene networks. This review focuses on synthesizing current advances in understanding the detrimental effects of heat stress on cereal crop production at the physiological and genetic levels. It provides an account of available genomic resources, genetic variation, candidate genes, and molecular markers for heat stress tolerance. Lastly, this review offers insight into crop genetic improvement for heat stress tolerance, including germplasm screening in glasshouse and field trials, marker-assisted selection, mapping genomic loci and identification of candidate genes, and genomic-assisted breeding. [ABSTRACT FROM AUTHOR]

Development of semi-dwarf wheat (Triticum aestivum) and rice (Oryza sativa) led to increased yields and agronomic efficiencies with less lodging. While these short-stature cereals have become common in global crop production, commercial maize (Zea mays L.) hybrids remain tall. There is no information currently available on plant N uptake or yield responses to N timing for short stature maize hybrids. We tested three hypotheses on short-stature and tall maize hybrids 1) short-stature maize hybrids would have similar yield response to in-season N application compared to tall hybrids, 2) short-stature maize hybrids would have similar dry matter and N uptake patterns to tall hybrids, and 3) there would be significant partitioning differences between short-stature and tall hybrids in dry matter and N within the plants at multiple growth stages. In ten side-by-side field trials across eight site-years in the Midwestern USA, we tested the yield response and underlying nitrogen physiology of short-stature maize hybrids and tall comparators to split-rate N application. We show that split-rate application of 50% of the total N at mid-vegetative stages (V6) averaged 0.24 t ha−1 more grain yield across 10 field trials (positive yield response in 6 out of 10 trials) compared to a single 100% up-front N application, with the same pattern for short-stature and tall hybrids. In both hybrid statures, V6 N applications showed more frequent improvement in grain yield than V12 N applications. Total N uptake at maturity was not different between short-stature hybrids and their tall counterparts (p = 0.62). N partitioning differed between short-stature and tall hybrids; leaves in short-stature hybrids had 5% higher N concentration and 13% more N content in early vegetative development, stalks had 18–27% less dry matter and 5–25% less N content, depending on growth stage, while R1 ears averaged 18% more dry matter and N accumulation (p < 0.10 in all cases). At maturity short-stature hybrids had 4% higher harvest index and 3% higher N harvest index (p < 0.10). Based on these results, we expect that N management recommendations in short-stature maize hybrids would be similar to their tall counterparts, but that short stature mitigates logistical risk by providing more flexibility for in-season N applications. This study provides a unique, robust dataset on yield and physiological response to split-rate N treatments in commercially relevant maize hybrids. • Short stature in maize simplifies in-season N application and later crop management. • Split-rate N applications at V6 increased hybrid yields 60% of the time, with similar patterns for short-stature and tall hybrids. • Overall, short-stature maize yielded similarly to tall comparators. • Short stature led to greater partitioning of N and dry matter to the grain than tall hybrids. • Greater flexibility for in-season N fertilization in short-stature maize reduces in-season application risks. [ABSTRACT FROM AUTHOR]

Yield-scaled nitrous oxide (N 2 O) emission (YSNE) has been recognized as a means for developing appropriate nitrogen (N) management strategies to balance food security and mitigating N 2 O emissions. To better understand and use the concept of YSNE, it is essential to be assessed under various field conditions. The main objectives of this study were to assess the relationship between N inputs and YSNE with published results and identify response patterns of YSNE to N inputs. We assessed the relationship between N inputs and YSNE using published results encompassing 1800 observations (published from 1980 to 2020) from maize, rice, and wheat crops worldwide. Background yield-scaled N 2 O emission (BYSNE; a YSNE in the condition of zero N input) was significantly different by crop type. Rice (90.8 ± 12.9 g N 2 O−N Mg−1) had lower BYSNE compared to maize (174.2 ± 30.1 g N 2 O−N Mg−1) and wheat (325.4 ± 41.8 g N 2 O−N Mg−1). BYSNE was positively correlated with annual mean temperature in maize, rice, and wheat fields. BYSNE was negatively correlated with soil total nitrogen contents in rice fields. Over 60% data set showed a positive relationship between N inputs and YSNE in all three crops studied. A small proportion of the dataset had an optimum N rate that minimized YSNE. The results suggest that in general, lower N input rates result in lower YSNE in crop production. YSNE can be reduced in three ways: increasing yields (Type 1), reducing N 2 O emissions (Type 2), and both increasing yields and reducing N 2 O emissions (Type 3). To identify appropriate measures, we suggest a N 2 O emission-yield curve combining responses of yields and N 2 O emissions to N inputs. In type 1, 2, and 3 measures, an N 2 O emission-yield curve is shifted to the right, down, and both right and down, respectively. Through identifying direction and magnitude of the shifting, the effects of applied measures on yields and N 2 O emission in N input levels can be easily compared and recognized. This study provided insights into the nature of YSNE and how YSNE responds to N inputs. It also suggested an N 2 O emission-yield curve, which can be useful to identify how certain measures affect both N 2 O emissions and crop yields. The information can be useful for scientific community and policymakers developing appropriate N management strategies to balance food security and the mitigation of N 2 O emissions. [Display omitted] • Background yield-scaled N 2 O emission (BYSNE) varied by crop type. • BYSNE was positively correlated with annual mean temperature. • Over 60% data sets showed consistently lower yield-scaled N 2 O emission as N input decreased. • N 2 O emission yield curve showed the effects of mitigation measures on both yields and N 2 O emission. [ABSTRACT FROM AUTHOR]

Climate change implications are a severe risk to food security and the economy. Global warming could disturb the production of both rainfed and irrigated agriculture thru the amplify of yield water requests in many areas. In this study, the fast-track projections available through the Inter-Sectors Impact Model Intercomparison Project (ISI-MIP) were presented and analyzed to assess the effects of two global warming (GW) levels (1.5 and 2.0 °C) on the maize and wheat yields in Egypt. Outcomes proposed spatial variations in the effects of temperature change on crop yield. Compared with the referenced situation, an observed national average change in wheat yield about 5.0% (0.0% to 9.0%) and 5.0% (−3.0% to 14.0%) under GW1.5 and GW2.0 respectively. While for maize yield, the change in national average about −1.0% (−5.0% to 3.0%) and −4.0% (−8.0% to 2.0%) under GW1.5 and GW2.0 respectively. GW1.5 could be helpful for wheat yield, but the positive effect decayed when the warming level reached 2.0 °C overhead the pre-industrial level. Nevertheless, the possible deviations to Egypt's maize production under the GW1.5 and GW2.0 scenarios are unclear where the models do not agree with the sign of change. Adjusting the temperature rise within 1.5 °C would diminish the yield reduction, as it is an extraordinary priority to safeguard crop production. To achieve Progress of innovative agronomic managing plans and swapping to additional drought-resistant crops may be valuable for coping with climate change in regions vulnerable to yield decline. [ABSTRACT FROM AUTHOR]

Soil salinity and climate change have a negative impact on global food production and security, especially in arid regions with limited water resources. Despite the importance of planting methods, irrigation, and soil amendments in improving crop yield, their combined impact on saline soil properties and cereal crop yield is unknown. Therefore, the current study investigated the combined effect of soil amendments (i.e., compost, C and zeolite, Z) and planting methods such as raised bed (M1) and conventional (M2), and different fractions of leaching requirements from irrigation water, such as 5% (L1) and 10% (L2), on the soil physio-chemical properties and wheat and maize productivity in an arid region. The combined application of C + Z, L2, and M1 decreased soil salinity (EC) and sodicity (ESP) after wheat production by 37.4 and 28.0%, respectively, and significantly decreased by these factors by 41.0 and 43.0% after a maize growing season. Accordingly, wheat and maize yield increased by 16.0% and 35.0%, respectively under such a combination of treatments, when compared to crops grown on unamended soil, irrigated with lower leaching fraction and planted using conventional methods. This demonstrates the significance of using a combination of organic and inorganic amendments, appropriate leaching requirements and the raised bed planting method as an environmentally friendly approach to reclaiming saline soils and improving cereal crop production, which is required for global food security. [ABSTRACT FROM AUTHOR]

The water footprint (WF) of crop production indicates the water consumption for crop growth in a specific area over a certain time, enabling comprehensive water use efficiency assessments to be achieved for different types of water in an irrigation district. Daily and monthly blue (irrigation water) and green (rainfall) water resources are unevenly distributed in monsoon climate areas. However, the intra-annual evolution of the WF of crop production for a monsoon irrigation district is lacking. In the current study, maize and wheat production in the Baojixia Irrigation District (BID) of Shaanxi in China selected as the case study for the period 2008–2017, where the WF of crop production was analyzed based on a regional distributed hydrological model and the associated meteorological driving factors on daily, monthly, and yearly scales were identified. Results reveal that the method of WF of crop production established in the study can be applied to hydrological simulation of irrigated areas without drainage system. The blue WFs of maize and wheat production accounted for 34% and 36% of the irrigation water supplies, respectively. On a yearly scale, precipitation had the greatest impact on the green and blue WFs of maize, while sunshine hours and temperature had the greatest impact on those of wheat, respectively. On daily and monthly scales, different meteorological factors played key roles in the WF of crop production in different typical years. The time scale effect existed in the impact of meteorological driving factors on the WF of crop production, reaching its maximum on a monthly scale. Both water shortages and water waste coexist in BID. The irrigated area should rationally allocate blue water and effectively utilize green water resource to improve crop yield. Meanwhile, the time scale effect in the WF assessment of crop production and driving factors cannot be neglected. The irrigation strategy should be adjusted to cope with the impact of meteorological conditions according to the results and actual situation. [Display omitted] • Daily and monthly water footprint of irrigated crops were analyzed. • Precipitation had the largest effect on the water footprint of maize. • Sunshine hours and temperature effected largest on the water footprint of wheat. • Monthly time scale effect of meteorological factors on water footprint was larger. [ABSTRACT FROM AUTHOR]