Response of Microbial Biomass Carbon and Nitrogen and Rice Quality in a Yellow Soil Paddy Field to Biochar Combined with Nitrogen Fertilizer

Abstract

The effects of biochar combined with nitrogen fertilizer on soil microbial carbon, nitrogen (SMBC, SMBN), and rice yield and quality were investigated to provide a scientific basis for soil fertilization and nitrogen fertilizer reduction. Using a field experiment, we set up a nitrogen reduction gradient (T0-T4):0, 10%, 20%, 30%, and 40% reductions. The same amount of biochar nitrogen was used as the substitute and no nitrogen fertilizer was used as the control (CK). The yield was measured and sampled at the mature stage of rice, and the samples were analyzed in the laboratory. The results showed that the range of SMBC and SMBN was 208.42-303.16 mg·kg-1 and 32.28-54.73 mg·kg-1, respectively. SMBC, SMBN, soil microbial entropy (qMB), soil microbial biomass nitrogen to total nitrogen ratio (SMBN/TN), and rice yield increased first and then decreased as the proportion of biochar and nitrogen fertilizer increased. SMBC, SMBN, and rice yield were all the highest in T2, which increased successively by 28.0%, 30.0%, and 13.4% compared with that of the T0 treatment (P<0.05), while those of the T4 treatment decreased slightly (P>0.05). The processing of SMBC, qMB, SMBN, and SMBN/TN showed a significantly positive relationship between the two (P<0.01). Compared with that of the T0 treatment, the T2 treatment significantly increased the Milled rice, gel consistency, and amylose content. In this study, the combination of biochar (5.0 t·hm-2) and nitrogen reduction (20%) effectively improved soil microbial carbon and nitrogen content and increased the yield and quality of rice, which could be a good choice for reducing nitrogen fertilization and increasing the efficiency of rice in a yellow soil paddy field in Guizhou.