Nitrogen fertilizer rates and irrigation rates throughout the study period.

1Con.W/M, Opt.W/M, W/M-M, W/S-M and M represent conventional and optimized winter wheat–summer maize, winter wheat–summer maize–spring maize, winter wheat–summer soybean–spring maize and spring maize treatment, respectively.2W, M1, M2, S and F represent winter wheat, summer maize, spring maize, summer soybean and fallow.3Denotes no data in the fallow season.

1.Con.W/M、Opt.W/M、W/M-M、W/S-M及M分别代表常规冬小麦-夏玉米（winter wheat–summer maize）轮作、优化冬小麦-夏玉米轮作、冬小麦-夏玉米-春玉米轮作、冬小麦-夏大豆-春玉米轮作及春玉米单作处理。2.W、M1、M2、S及F分别代表冬小麦（winter wheat）、夏玉米（summer maize）、春玉米（spring maize）、夏大豆（summer soybean）及休耕地（fallow）。3.休耕季无相关数据。