Abstract: A field experiment was conducted to investigate the effects of tillage methods and crop rotation models on soil enzyme activities and physicochemical properties during different growth periods in an oasis irrigation region of Northwest China. There were three crop rotation models, including wheat/maize intercropping (W//M), wheat and maize rotation (WM), and wheat after planting winter rape in rotation with maize (WGM), with two tillage methods (30cm stubble and no tillage, NT; conventional tillage, CT) being applied for each rotation model. Results showed that the activities of soil sucrase and amylase increased first and then decreased under different treatments, while the activities of urease and protease gradually increased. Soil enzyme activity of NTW was increased by 13.00%, 7.50% and 30.61% than that of NTM, NTW-G-M and NTSM, respectively. Soil total nitrogen and phosphorus concentrations were 59.52%-87.14% and 20.00%-66.67% lower at maize maturity than at wheat sowing, respectively. Soil bulk density was the lowest at wheat sowing, being 3.47%-11.03% lower than that at maizematurity stage. Soil porosity was negatively correlated to soil bulk density. There was no significant difference (P>0.05) in maize yield among different treatments. NTW//M treatment had the best performance in soil structure and nutrient status. Therefore, wheat/maize intercropping with no-tillage straw returning should be a useful method for maintaining land productivity, which is worth popularizing in oasis agricultural area.

Key words: intercropping, rotation, no-tillage, soil enzyme activity, soil physicochemical properties.