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Climate extremes can negatively impact crop production, and climate change is expected to affect the frequency and severity of extremes. Using a combination of in situ station measurements (Global Historical Climatology Network's Daily data set) and multiple other gridded data products, a derived 1° data set of growing season climate indices and extremes is compiled over the major growing regions for maize, wheat, soybean, and rice for 1951–2006. This data set contains growing season climate indices that are agriculturally relevant, such as the number of hot days, duration of dry spells, and rainfall intensity. Before 1980, temperature‐related indices had few trends; after 1980, statistically significant warming trends exist for each crop in the majority of growing regions. In particular, crops have increasingly been exposed to extreme hot temperatures, above which yields have been shown to decline. Rainfall trends are less consistent compared to temperature, with some regions receiving more rainfall and others less. Anomalous temperature and precipitation conditions are shown to often occur concurrently, with dry growing seasons more likely to be hotter, have larger drought indices, and have larger vapor pressure deficits. This leads to the confluence of a variety of climate conditions that negatively impact crop yields. These results show a consistent increase in global agricultural exposure to negative climate conditions since 1980.

Food demands are rising due to an increasing population with changing food preferences, placing pressure on agricultural production. Additionally, climate extremes have recently highlighted the vulnerability of the agricultural system to climate variability. This study seeks to fill two important gaps in current knowledge: how irrigation impacts the large-scale response of crops to varying climate conditions and how we can explicitly account for uncertainty in yield response to climate. To address these, we developed a statistical model to quantitatively estimate historical and future impacts of climate change and irrigation on US county-level crop yields with uncertainty explicitly treated. Historical climate and crop yield data for 1970-2009 were used over different growing regions to fit the model, and five CMIP5 climate projections were applied to simulate future crop yield response to climate. Maize and spring wheat yields are projected to experience decreasing trends with all models in agreement. Winter wheat yields in the Northwest will see an increasing trend. Results for soybean and winter wheat in the South are more complicated, as irrigation can change the trend in projected yields. The comparison between projected crop yield time series for rainfed and irrigated cases indicates that irrigation can buffer against climate variability that could lead to negative yield anomalies. Through trend analysis of the predictors, the trend in crop yield is mainly driven by projected trends in temperature-related indices, and county-level trend analysis shows regional differences are negligible. This framework provides estimates of the impact of climate and irrigation on US crop yields for the 21st century that account for the full uncertainty of climate variables and the range of crop response. The results of this study can contribute to decision making about crop choice and water use in an uncertain future climate.

In several parts of the world, the prevalence and severity of drought are predicted to increase, creating considerable pressure on global agricultural yield. Among all abiotic stresses, drought is anticipated to produce the most substantial impact on soil biota and plants, along with complex environmental impacts on other ecological systems. Being sessile, plants tend to be the least resilient to drought-induced osmotic stress, which reduces nutrient accessibility due to soil heterogeneity and limits nutrient access to the root system. Drought tolerance is a complex quantitative trait regulated by multiple genes, and it is one of the most challenging characteristics to study and classify. Fortunately, the clustered regularly interspaced short palindromic repeat (CRISPR) technology has paved the way as a new frontier in crop improvement, thereby revolutionizing plant breeding. The application of CRISPER systems has proven groundbreaking across numerous biological fields, particularly in biomedicine and agriculture. The present review highlights the principle and optimization of CRISPR systems and their implementation for crop improvement, particularly in terms of drought tolerance, yield, and domestication. Furthermore, we address the ways in which innovative genome editing tools can help recognize and modify novel genes coffering drought tolerance. We anticipate the establishment of effective strategies of crop yield improvement in water-limited regions through collaborative efforts in the near future.

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