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In the semi-arid Loess Plateau region, water stress is the main limiting factor for rainfed agriculture; thus, conservation agriculture has been proposed to address this problem in these areas. Since 2007, a middle- to long-term experiment was established in Heyang County, Shaanxi, a region typical of the Loess Plateau, to evaluate the impact of no-tillage (NT), subsoiling tillage (ST) and conventional tillage (CT) on crop yield, water use, and soil water dynamics for winter wheat (Triticum aestivum L.) continuous cropping (WWC), spring maize (Zea mays L) continuous cropping (SMC), and spring maize-winter wheat rotation cropping (MWR) systems. The highest four-year average wheat yield amounting to 5958 kg ha(-1) was attained in MWR-ST, while the highest maize yield advantage averaging 772 kg ha(-1) was obtained in SMC-NT. There were no significant differences in evapotranspiration (ET) and soil water storage (SWS) at the sowing/harvest stage among all treatments, but the relative greater average SWS before sowing was maintained under conservation tillage practices. The highest water use efficiency (WUE) reaching 10.0 kg ha(-1) mm(-1) for wheat in MWR and 20.3 kg ha(-1) mm(-1) for maize in SMC was obtained under ST treatment, while the significant WUE advantage of NT compared with CT was only obtained in SMC. At key growth stages, the higher soil water content (SWC) in the 0-200 cm soil profile was maintained in the conservation tillage and MWR system for wheat but in the conservation tillage and SMC system for maize. The longer-duration fallows did not produce a better effect on SWS at the sowing stage, while the reduction of soil disturbance enhanced SWS compared with CT.

In summary, tillage, cropping system, and their interaction effect produced significant effects on crop production and soil water status, and the above findings might be helpful to draft appropriate management strategies to realize optimal crop yield based on water use.