Soil aggregate and crop yield changes with different rates of straw incorporation in semiarid areas of northwest China

• Straw incorporation was effective in improving soil physical properties.
• Straw incorporation was effective in changing soil chemical properties.
• Straw incorporation treatments significantly improved the soil water storage.
• Straw incorporation produced significantly increased grain yields and WUE.

The current cropping system of conventional tillage and stubble removal in the northwestern Loess Plateau of China is known to decrease the water use efficiency and crop yield because of reduced aggregation and aggregate stability, as well as degrading other soil properties. To determine the effects of straw incorporation on the soil aggregates and crop yield, we conducted experiments in semiarid areas of southern Ningxia for 4 years (2007–2010). Four treatments were tested: (i) no straw incorporation (CK); (ii) incorporation of maize straw at a low rate of 4500 kg/ha (L); (iii) incorporation of maize straw at a medium rate of 9000 kg/ha (M); and (iv) incorporation of maize straw at a high rate of 13 500 kg/ha (H). In the final year of treatment (2010), the mean soil bulk density of the tilth soil (0–60 cm) was decreased significantly with H, M and L, i.e., by 4.13%, 3.21% and 1.80% compared with CK, respectively, and the treatments greatly improved the total soil porosity. The straw incorporation treatments increased the soil aggregate size distribution and soil aggregate stability in the 0–40 cm soil layers, according to the following order: H/M > L > CK. Straw incorporation significantly improved the soil moisture content compared with CK. Higher yields coupled with greater water use efficiency were achieved with H, M and L compared with CK, where these treatments increased the crop yields by 22.49%, 22.82%, and 10.62%, respectively, and the water use efficiency by 32.11%, 29.29%, and 14.05%.