黄壤稻田土壤微生物量碳氮及水稻品质对生物炭配施氮肥的响应

探讨生物炭与氮肥减量配施对黄壤稻田土壤微生物碳、氮（SMBC、SMBN）和稻谷产量及品质的影响，旨在为该区域土壤培肥及氮肥减施增效提供科学依据.采用大田试验，设置5个氮肥减施梯度（T0~T4）：0、10%、20%、30%和40%，用等氮量生物炭氮替代，以不施氮肥为对照（CK），在水稻成熟期进行测产采样，并对样品进行室内分析.结果表明，生物炭与氮肥减量配施处理的SMBC和SMBN变化范围分别在208.42~303.16 mg·kg^-1和32.28~54.73 mg·kg^-1之间.SMBC、SMBN、土壤微生物熵（qMB）、土壤微生物量氮与全氮比值（SMBN/TN）及稻谷产量随生物炭与氮肥配施比例的增加均呈先增加后降低趋势，T2处理的SMBC、SMBN及稻谷产量均最高，较T0处理依次增加了28.0%、30.0%和13.4%（P<0.05），而T4处理略有降低（P>0.05）.各处理的SMBC、qMB、SMBN及SMBN/TN两两之间均呈极显著正相关关系（P<0.01）.与T0处理相比，T2处理可显著增加稻米精米率、胶稠度和直链淀粉含量.本试验条件下生物炭（5.0 t·hm^-2）与氮肥减量（20%）配施可有效提高土壤微生物量碳氮，稻谷增产提质，可作为贵州黄壤稻田水稻氮肥减施增效的较好选择.

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

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.