Effects of tillage and straw returning on soil fertility and grain yield in a wheat-rice double cropping system

Four treatments(no-tillage + straw mulching, NTS; no-tillage + high stubble remaining, NTH; conventional tillage + straw incorporation, CTS and conventional tillage + no straw returning, CT) were designed to investigate the effects of tillage and straw returning on soil fertility and grain yield in a wheat-rice double cropping system. The experiments were conducted under field condition and by means of micro-plots in isolated concrete ponds, respectively, and lasted for consecutive three years. Results showed that no tillage increased soil bulk density and penetration resistance, but straw returning significantly improved soil structure and increased soil nutrients content. After three years straw returning, soil organic matter, total N, available P and K in CTS treatment increased by 4.7%～13.0%, 0%～10.6%, 0.2%～10.6% and 8.4%～15.5%, respectively, compared with that in CT. Both positive and negative effects of straw returning on wheat yield were observed over three years, but NTS and NTH decreased wheat yield, compared with CT. On the average, wheat yield decreased approximately by 1% due to straw returning. However, rice yield was the highest in CTS and increased approximately by 3%, on the average, compared with that in CT. Therefore, no tillage combined with straw mulching or high stubble remaining was practical in saving labor and cost and maintaining soil fertility, while conventional tillage with straw incorporation was a beneficial option in sustaining soil fertility and increasing crop yield.