保护性耕作下陇东春玉米-冬小麦-夏大豆轮作系统土壤水分动态及水分利用效率

在黄土高原西部连续5年定位观测了4种耕作措施[传统耕作(T);传统耕作 秸秆覆盖(TS);免耕(NT)和免耕 秸秆覆盖(NTS)]下春玉米-冬小麦-夏大豆轮作系统中的水分动态及其水分利用效率,结果表明:土壤含水量受降水的影响较大,年内和年际的变率大,200 cm内土壤含水量在350～600 mm变动;土壤贮水量5-7月上旬因作物利用迅速下降,在雨季得到补充,到冬季缓慢下降;水保耕作措施对玉米Zeamnys、小麦Triticum aestivum和大豆Glycine max生育期200 cm土体耗水量影响不大,但秸秆覆盖能有效增加玉米-小麦-大豆轮作系统的水分利用效率;与传统耕作相比,免耕没有造成轮作系统的减产和水分利用效率的降低,免耕、秸秆覆盖可增加农民收入;在土地利用强度极高的玉米-小麦-大豆轮作系统,改大豆为利用营养体的豆科牧草,可提高系统的水分和光能利用率.

Dynamics of soil water and water use efficiency within Maize-Winter Wheat-Soybean rotation under different tillage treatments in the Longdong Loess Plateau

A five years field experiment was conducted to determine the effects of conventional tillage(T),conventional tillage with stubble retention(TS),no tillage(NT) and no tillage with stubble retention(NTS)treatment on soil water dynamics and water use efficiency(WUE) under maize-wheat-soybean rotation system in the western Loess Plateau,Gansu.The Results showed that rainfall variation is large in the region and affected on soil water content and varied greatly within and among years.The soil water content in the 200 cm soil profile fluctuated between 300 and 600 mm.Soil water content decreased rapidly from May to early July because of peak crop growth,and recharged by summer rainfall until October,then decreased slowly over winter(Though conservation tillage had no obviously effect on evapotranspiration for maize,soybean and wheat crops down to two meters).Tillage had no obviously effect on the soil water consumptions in the 200 cm soil profile for all crops,however stubble retention increases the WUE of rotation system significantly.Comparing to conventional tillage,WUE under no-till treatment was similar to that under conventional one.Hence conservation tillage can increase the local farmer income by reducing the cultivation cost and anergy.It is suggested that replacement of soybean with a annual forage legume in the maize-wheat-soybean rotation could increase the WUE and RUE(radiation use efficiency).