Effects of combining biochar-based fertilizer and milk vetch on dry matter accumulation and N use efficiencies of early rice in reddish paddy field of south China

Objectives Studying the effect of co-incorporating of biochar-based fertilizer and green manure on rice yield and nutrient uptake in reddish paddy field to find a environmental friendly way to to realize the reuse of straw and the reduction of nitrogen fertilizer in rice production.

Methods A pot rice experiment was conducted, and 5 treatments were setup, i.e. no N fertilizer (CK₀), applying 100% N fertilizer (CK₁), and reducing 20% of chemical N rate, combined with milk vetch incorporation (MV), biochar-based fertilizer (BF) and both MV incorporation and BF (MV + BF). The dry matter weight of rice shoot (i.e., grain and straw) and yield components were investigated, and the N uptake and use efficiencies of the early rice plant were analyzed.

Results Compared to CK₁, the rice grain yields were increased significantly as the higher 1000-grain weight and effective panicle numbers in treatments of BF + MV and BF, and the physiological efficiency of N (\rmPE_\rmN) were also increased. The rice grain yield was increased by 11.8% in BF + MV and 7.52% in BF (P < 0.05), the dry matter weight of grain and above ground part of rice were significantly increased by 11.8% and 7.62%, and the N accumulation in aboveground part was increased by 10.9% in treatment of MV (P < 0.05). According to Pearson correlation analysis, the 1000-grain weight and N accumulation in rice grain were remarkably and positively correlated to incorporate MV (P < 0.05), and the physiological efficiency of N and dry matter production efficiency of N were remarkably and positively correlated to combination of BF under the condition of reducing 20% N fertilizer input respectively.

Conclusions Under the condition of not reducing early rice yield in reddish paddy field, incorporation of biochar and green manure with 20% less nitrogen input can not only improve the utilization rate of crop straw resources, but also reduce the application amount of nitrogen fertilizer in rice field, and improve the utilization rate of nitrogen. Therefore, it is an prospective way of fully using straw and soil resources in the production of early rice in reddish paddy fields, south China.