Crop water requirements are directly affected by climatic variability, especially for crops grown in the areas which are sensitive to climatic change. Based on the SIMETAW model and a long-term meteorological dataset, we evaluated the spatiotemporal variations of climatic change impacts on water requirement of oat in North and Northeast China. The results indicated that effective rainfall showed an increasing trend, while the crop water requirement and irrigation demand presented decreasing trends over the past decades. The water requirement of oat showed significant longitudinal and latitudinal spatial variations, with a downtrend from north to south and uptrend from east to west. Climatic factors have obviously changed in the growth season of oat, with upward trends in the average temperature and precipitation, and downward trends in the average wind speed, sunshine hours, relative humidity, and solar radiation. Declines in solar radiation and wind speed, accompanied with the increase in effective rainfall, have contributed to the reduced crop water requirement over these decades. Given the complex dynamic of climate change, when studying the impact of climate change on crop water requirements, we should not only consider single factors such as temperature or rainfall, we need to analyze the comprehensive effects of various climatic factors.

Confronted with the great challenges of globally growing populations and food shortages, society must achieve future food security by increasing grain output and narrowing the gap between potential yields and farmers’ actual yields. This study attempts to diagnose the climatic and agronomic dimensions of oat yield gaps and further to explore their restrictions. A conceptual framework was put forward to analyze the different dimensions of yield gaps and their limiting factors. We quantified the potential yield (Yp), attainable yield (Yt), experimental yield (Ye), and farmers’ actual yield (Ya) of oat, and evaluated three levels of yield gaps in a rain-fed cropping system in North and Northeast China (NC and NEC, respectively). The results showed that there were great differences in the spatial distributions of the four kinds of yields and three yield gaps. The average yield gap between Yt and Ye (YG-II) was greater than the yield gap between Yp and Yt (YG-I). The yield gap between Ye and Ya (YG-III) was the largest among the three yield gaps at most sites, which indicated that farmers have great potential to increase their crop yields. Due to non-controllable climatic conditions (e.g., light and temperature) for obtaining Yp, reducing YG-I is extremely difficult. Although YG-II could be narrowed through enriching soil nutrients, it is not easy to improve soil quality in the short term. In contrast, narrowing YG-III is the most feasible for farmers by means of introducing high-yield crop varieties and optimizing agronomic managements (e.g., properly adjusting sowing dates and planting density). This study figured out various dimensions of yield gaps and investigated their limiting factors, which should be helpful to increase farmers’ yields and regional crop production, as long as these restrictions are well addressed.

Hebei Province is a typical water-scarce agricultural region in North China. Quantifying the water demands of major crops and their variations in this region is crucial for the sustainable use of agricultural water resources. Based on meteorological data and crop growth parameters of 21 national weather stations in Hebei Province from 2007 to 2017, this study analyzed the crop water requirement, irrigation water demand, and water deficit index and their dynamic changes for several grain and vegetable crops including winter wheat, summer maize, soybean, potato, tomato, cucumber, eggplant, cowpea, Chinese cabbage, cabbage, and carrot. In addition, regional total irrigation water demands of these water-intensive crops were estimated. The results indicated that, except for summer maize, the crop water requirements and irrigation water demands of grain crops during the growth periods were mostly higher than those of vegetable crops. Winter wheat and cabbage had the highest water deficits among grain and vegetable crops, respectively, while summer maize had the lowest water deficits. Temporally, the irrigation water demands of winter wheat, summer maize, cabbage, and eggplant have increased for years, along with the increase in planting areas. Spatially, the total irrigation water demand in the southeast of Hebei Province was higher than that in the northwest, and the total irrigation water demand of winter wheat was much higher than that of the other crops. To mitigate water scarcity while ensuring food security, the planting areas of crops with higher yields and lower water consumptions, including summer maize, potato, cabbage, and carrot could be appropriately expanded. In contrast, the scale of water-intensive crops such as winter wheat and tomato should be strictly controlled. Our findings will be of great significance for constructing sustainable water-saving cropping systems in a changing climate.