Soil Water Content at Planting Affects Determining Agricultural Drought for Rainfed Spring Wheat

Agricultural drought often refers to water deficit in soil caused by a shortage of precipitation during a specific period in crop growing season, thus leading to final crop production failure. However, soil water content during planting may be related to the final yield of crop. Therefore, the soil water content at planting could have a great impact on determining whether agricultural drought occurs during crop growth and development. In the current study, we used soil water content at planting at 0-50 cm depth, the spring wheat (Triticum aestivum L.) yield from 1987 to 2011, and precipitation from 1971 to 2011 at Dingxi, Gansu Province, China, intending to quantify the influence of soil water content at planting on determining agricultural drought for rainfed spring wheat. The response of spring wheat yield to growing season precipitation comprised two different linear relationships defined by whether the soil water content at planting was greater or less than 100 mm. With the identical amount of soil water content at planting and precipitation during main growth period, a higher soil water content at planting resulted in a greater spring wheat yield. Soil water content at planting was more effective than growing season precipitation for increasing spring wheat yield. According to the probability distributions of soil water content during planting and growing season precipitation, we concluded that 28.6% of the years studued involved agricultural drought for rainfed spring wheat in the Dingxi of Gansu province, China. This analysis, which quantified the relative importance of soil water content at planting (29.97 kg ha(-1) per mm) and during growing season precipitation (12.21 kg ha(-1) per mm) to determine yield and agricultural drought occurrence for spring wheat, suggests that improving the amount of soil water storage before crop planting is an important way to deal with agricultural drought.