Effects of straw incorporation on the soil nutrient contents, enzyme activities, and crop yield in a semiarid region of China

• Straw incorporation was effective in increasing soil organic carbon content.
• Straw incorporation was effective in improving soil N and P contents in 0–20 cm layer.
• Straw incorporation treatments significantly increased the soil enzyme activities levels.
• Straw incorporation produced significantly increased the crop 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 soil infertile and degradation. To determine the effects of straw incorporation on the soil fertility 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−1 (L); (iii) incorporation of maize straw at a medium rate of 9000 kg ha−1 (M); and (iv) incorporation of maize straw at a high rate of 13500 kg ha−1 (H). After straw incorporation for four years, the results showed that variable straw amounts had different effects on the soil fertility indices, where H treatment had the greatest effect. Compared with CK, the average soil available N, total N, available P, total P, and SOC levels under straw incorporation treatments were 27.5%, 10.8%, 16.6%, 5.2%, and 9.8% higher in 0–40 cm soil layers, especially in 0–20 cm soil layer. The straw incorporation treatments average increased the soil urease, phosphatase, and invertase activities levels by 19.6%, 39.4%, and 44.3% in 0–60 cm soil layers, according to the following order: H > M > L > CK. And higher yields coupled with higher nutrient contents were achieved with H, M and L compared with CK, where these treatments increased the crop yields by 22.5%, 22.8%, and 10.6%, and water use efficiency by 34.6%, 30.7%, and 15.7%, respectively. Our results suggest that straw incorporation (especially in rate of 13500 kg ha−1) is an effective practice for improving the soil fertility and increased crop yield in semiarid region of China.