[Effects of different planting patterns on the apparent balance of soil nutrients and nitrogen production efficiency in paddy soil].

To investigate the effects of different planting patterns on soil nutrient contents, rice yield, nitrogen production efficiency, and apparent nutrient balance, a long-term field experiment was conducted in Changsha, Hunan, China. Four planting patterns were examined, including winter fallow-double cropping rice (CK), ryegrass-double cropping rice (Ry-R-R), Chinese milk vetch-double cropping rice (Mv-R-R), rape-double cropping rice (Ra-R-R). Compared with CK, soil total nitrogen (N) and available N were significantly higher under Ry-R-R, Mv-R-R and Ra-R-R. However, soil available potassium (K) content in CK was significantly higher than that in the other treatments. In addition, the N partial factor productivity in the late rice cropping was significantly higher under Ry-R-R, Mv-R-R and Ra-R-R. The N accumulation in panicles, stems and leaves of late rice under Ry-R-R, Mv-R-R and Ra-R-R were significantly higher than that in CK. Furthermore, the rice yield in Ry-R-R and Mv-R-R were significantly higher in comparison to CK. A significant positive correlation between grain yield and soil N content was observed. Compared with CK, Ry-R-R and Mv-R-R significantly increased the surplus of soil N and phosphorus content, but Ry-R-R and Ra-R-R increased the surplus of K content. Overall, winter crop-double rice cropping system could improve soil nutrient contents and N production efficiency, alleviate K deficiency, which would be beneficial to soil nutrient balance of paddy soils. Given the high surplus of N in paddy soils, N fertilizers should be reduced.