Agriculture in the semiarid area of northern China is increasingly threatened by soil drought in recent decades. Soil moisture has been substantially affected by the coupled impacts of climate change and agricultural practices. However, the impact of climatic change and agricultural practices on soil drought lacks substantial observational evidence and needs further investigation. Moreover, this drying trend is likely to contribute to an increasing scarcity of water resources in the agricultural ecosystem, which may be in turn threaten food security. We analyzed the 32-year (1983-2014) in-situ measurements of soil moisture collected in agricultural experiment plots in the semiarid area of northern China and found that a decrease in soil moisture content of crop fields (0-50 cm soil layers) affected by climate change. Through three field experiments (0-100 cm soil layers), we attempt to understand the effect of agricultural practices on soil drought. In the first experiment, we compared the impact of different cropping patterns (continuous and rotation cropping) on soil moisture. In the second experiment, we designed six gradients to show the influence of different fertilizer levels on soil moisture. In the third experiment, we examined the impact of different tillage methods (no-tillage and tillage) on soil moisture.
We find that the warming-drying trend leads to soil drought (reduced by 8.1%), and agronomic practices aggravated soil drought. Excessive fertilization and tillage (0-30 cm) consume more soil water (about 38% and 21.5%, respectively) compared to control experiments with lower water use efficiency. Water use efficiency in rotation cropping field is 23.7-31.5% higher than that in continuous cropping field. We suggest that reasonable strategies to mitigate soil drought in semiarid regions, such as adjustment in the cropping system, reduction of fertilizer use, and improvement of conservation tillage. The balance between food security and water resource in agriculture ecosystem should be considered in the studies of climate change impact on agriculture.