Soil nitrate–N residue, loss and accumulation affected by soil surface management and precipitation in a winter wheat-summer fallow system on dryland

Soil nitrate–N residue after harvesting crops and nitrate–N loss during the following fallow season is serious concern for the agricultural environment in dryland. A 6-year-long, location-fixed field experiment was conducted to determine the effects of plastic film mulch (PM), straw mulch (SM), green manure (GM) and straw mulch plus green manure (SGM) on the nitrate–N residue, loss and accumulation in a winter wheat-summer fallow system. Compared with the bare fallow, average grain yield was increased by 6 % with PM, whereas decreased by 7, 5 and 5 % with SM, GM and SGM, respectively. Average total N uptake was decreased by 13 % with SM, but not affected by PM, GM and SGM. Average nitrate–N residue at wheat harvest was decreased by 35, 32 and 18 % with PM, SM and SGM, respectively, but not affected by GM. Average soil water recharge was increased by 12 % with PM, and not affected by SM, whereas decreased by 20 and 16 % with GM and SGM, respectively. For the PM, SM, GM and SGM, the average nitrate–N loss from top soil was decreased by 51, 53, 50 and 34 %, respectively, and the average nitrate–N accumulation in deep soil was decreased by 56, 45, 31 and 39 %. Above results revealed that increasing the yield decreased soil nitrate–N residue, and nitrate–N loss and accumulation was restricted by the decreased nitrate–N residue and soil water recharge. Overall, PM is a preferable measure for the decreased nitrate–N residue, loss and accumulation, at the same time increased the yield in dryland.