Effects of tillage and irrigation on water use and yield of farmland crops

Abstract：Irrigation and tillage able to maintain a healthy plow layer for sustainable production of winter wheat-summer maize rotation cropping system in North China Plain was experimentally studied in this paper. We investigated three tillages: deep subsoiling (ST), deep subsoiling+ straw incorporation (ST+RS) and conventional rotary tillage (RT) from 2015 to 2016 in Xinxiang, Henan province. The irrigation for each tillage was based on soil moisture in which irrigation was assumed whenever the moisture content in the wet soil layer dropped to 60% of the field capacity (H), 50% of the field capacity (M) and 40% of the field capacity(L), respectively. In each treatment, we measured the yield and water use efficiency (WUE) of the crops. The results showed that ST and ST+RS reduced soil bulk density and increased soil porosity and field holding capacity, especially ST+RS. Compared with RT, ST and ST+RS, on average, reduced the bulk density of 0-40 cm soil by 5.0% and 6.0% respectively, and increased its porosity by 6.9% and 8.0% respectively, field capacity by 6.2% and 12.8% respectively, and saturated water content by 6.2% and 5.7% respectively. The tillage and irrigation combined to significantly increase water storage in 0-100 cm soil in winter. In particular, ST and ST+RS increased water storage (SWS) in the 0-100 cm soil by 11.0% and 15.8%, respectively, compared to RT. SWS under H and M irrigation treatment increased by 18.1% and 11.1%, respectively, compared with L irrigation. Tillage affected yield and WUE of both winter wheat and summer maize at significant level. Compared to RT, ST and ST+RS increased annual yield by 9.2% and 15.5%, respectively, and WUE by 11.2% and 15.3%, respectively. Irrigation affected yields and WUE of the crops as well. While the yields increased with the controlled soil moisture for irrigation, the M irrigation treatment gave the highest WUE. Under the current soil and climatic condition, deep subsoiling coupled with straw incorporation and an appropriate water management appears to offer a best solution to constructing plow layer and increasing WUE and crop yield. In particular, to best balance yield, water consumption and water use efficiency of the crops under conventional rainfall condition, the optimal tillage is to loosen the soil up to a depth of 35cm combined with incorporating straw prior to sowing the winter wheat. The crops are then irrigated whenever the moisture content in the wet layer drop to 50% of the field capacity. This study is for winter wheat-summer maize rotation system in Henna province, and the lines of the wheat and the maize used in the study were "Aikang 58" and "Denghai 605" respectively, but the results have implications in other regions in North China Plain.