Abstract: In order to find a solution to the ecological problem of, soil erosion in sloping farmland in coal-mining subsidence areas, a field experiment was conducted to explore effects of tillage on water use efficiency (WUE) and grain yield of summer maize. It was designed to have four tillage methods, that is, flat tillage (CK), flat tillage + stubble mulching (T1), contour ridge tillage (T2), and contour ridge tillage + stubble mulching (T3). Results show that stubble mulch lowered significantly unnecessary evaporation during the seedling and jointing stages(P<0.05). As a result, soil water content in the 0-100cm soil layers was 9.64% and 9.74% higher in T1 and T3, respectively, than in CK at the jointing stage. After the jointing stage, though there was much rain, surface run-off was much less in T1, T2 and T3 than in CK, suggesting that T1, T2 and T3 improved their water and nutrient retaining capacities. Hence, T1, T2 and T3 was also significantly higher in grian yield, WUE, rainfall use efficiency and N partial factor productivity than CK(P<0.05). The effect of T3 reducing soil nutrient and water losses was more significant than the others. Besides, T3 was 16.59%, 31.19%, 16.55% and 16.59% higher than CK in grian yield, WUE, rainfall use efficiency and N partial factor productivity, respectively. Therefore, T3, that is, contour ridge tillage plus stubble mulching,is an effective tillage method applicable to sloping farmland in coal-mining subsidence areas.

Key words: coal-mining subsidence area, sloping farmland, contour ridge tilllage, stubble mulching, summer maize