Improved crop yield and reduced nitrate nitrogen leaching with straw return in a rice-wheat rotation of Ningxia irrigation district

Field experiments were conducted in rice-wheat rotation under conventional management to determine the effects of straw return ((half straw return, HS) and (total straw return, TS)) on crop yield, N uptake, soil properties and soil NO3−–N leaching. We found that straw return significantly increased crop yield and N uptake. TS significantly increased soil SOM at depths of 20 cm and 30 cm. Straw return had significantly increased soil NO3−–N leaching at a depth of 10 cm, whereas significantly decreased soil NO3−–N leaching at depths of 30 cm and 90 cm in the rice season. In wheat season, HS and TS performed better than conventional fertilization management without straw return in reducing soil NO3−–N leaching at depth of 90 cm. Soil NO3−–N leaching was significantly decreased through enhancing total N uptake, improving soil aggregation and decreasing soil NO3−–N concentration. Our results indicated that total straw return has the potential to increase crop yield, improve soil aggregation and decrease soil NO3−–N concentration, thus increasing total N uptake and reducing soil NO3−–N leaching in the rice-wheat rotation system of Ningxia Yellow river irrigation district. In the future, the long-term observation of crop yield and nitrate nitrogen leaching are necessary to identify the environmentally friendly straw return practices for rice-wheat rotation.