RESUMO
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.
Assuntos
Fertilizantes , Oryza , Agricultura , Biomassa , Carbono , Carvão Vegetal , Nitrogênio/análise , SoloRESUMO
Reducing the application of chemical fertilizer and increasing fertilizer efficiency can contribute to the sustainable development of agriculture. To evaluate the impacts of N fertilizer reduction and biochar application on soil organic carbon active components and mineralization in yellow soil, an experiment was carried out with five different substitution rates of chemical N fertilizer by biochar under the same rate of N input, i.e., 0, 10%, 20%, 30%, 40% (CK, T1-T4). The results showed that chemical N fertilizer reduction combined with biochar application could significantly improve soil organic carbon (SOC), the magnitude of which was proportional to the amount of biochar application. Under the condition of 20% substitution rate (T2), soil microbial biomass carbon (MBC) and readily oxidized carbon (ROC) were the highest with 293.68 mg·kg-1 and 250.00 mg·kg-1, respectively, but the concentration of soil dissolved organic carbon (DOC) was the lowest. SOC mineralization rate reached the highest on the third day of incubation. Then, it decreased rapidly in the early period (day 3 of incubation to day 6), decreased slowly in the middle period (day 6 of incubation to day 18), and stabilized in the later period (day 18 of incubation to day 30). There was a logarithmic relationship between mineralization rate of soil organic carbon and incubation time. SOC cumulative mineralization amount and cumulative mineralization rate were the lowest in the T2 treatment with 0.66-0.86 g·kg-1 and 2.9%-4.0%, respectively. As the substitution rate of chemical N fertilizer by biochar increased, rice yield increased firstly and then decreased. Rice yield in the T2 treatment was the highest, which increased by 13.4% compared with the CK. The substitution of 20% chemical N fertilizer with biochar (5 t·hm-2) could effectively improve the contents of SOC, MBC, ROC, and rice yield, reduce the cumulative mineralization amount of organic carbon and cumulative mineralization rate, and enhance the capacity of soil carbon sequestration. Hence, it could be the most effective fertilizer practice for improving soil fertility and rice yield in paddy field of yellow soil in Guizhou Province.
