Chinese Milk Vetch Improves Plant Growth, Development and 15 N Recovery in the Rice-Based Rotation System of South China.

Chinese milk vetch (CMV) is vital for agriculture and environment in China. A pot experiment combined with ¹⁵ N labeling (including three treatments: control, no fertilizer N and CMV; ¹⁵ N-labeled urea alone, ¹⁵ NU; substituting partial ¹⁵ NU with CMV, ¹⁵ NU-M) was conducted to evaluate the impact of CMV on plant growth, development and ¹⁵ NU recovery in rice-based rotation system. The ¹⁵ NU-M mitigated oxidative damage by increasing antioxidant enzymes activities and chlorophyll content while decreased malondialdehyde content in rice root and shoot, increased the biomass, total N and ¹⁵ N uptake of plant shoots by 8%, 12% and 39% respectively, thus inducing a noticeable increase of annual ¹⁵ N recovery by 77% versus ¹⁵ NU alone. Remarkable increases in soil NH ₄ ⁺ and populations of bacteria, actinomycetes and azotobacter were obtained in legume-rice rotation system while an adverse result was observed in soil NO ₃ ^- content versus fallow-rice. CMV as green manure significantly increased the fungal population which was decreased with cultivating CMV as cover crop. Therefore, including legume cover crop in rice-based rotation system improves plant growth and development, annual N conservation and recovery probably by altering soil nitrogen forms plus ameliorating soil microbial communities and antioxidant system which alleviates oxidative damages in plants.