Effects Of Biochar On Acidity Reduction Of Red Soil And Soybean Growth

Acid red soil distributes widely in south China. Its strong acidity deteriorates the growth condition of crop, reduces the activity of soil fertility, limits the crop growth and influences greatly the water and temperature effect in south China.In order to study effects of biochar on soil acidity and fertility, to explore effects of biochar combined with lime on soil improvement and seek for a suitable improvement scheme for red soil. We choose the quaternary red soil for this study, which is widely distributed in the south China, and make a soybean pot experiment with three different biochar treatments (2%C,5%C and 10%C), one lime treatment (Ca) and one contrast check (CK). Effects of biochar on soil acidity, fertility and growth of soybean are revealed. Meanwhile, another pot experiment is designed with different proportion of biochar and lime. It containes 6 treatments CK、C4 (2%C)、Ca4 (3954.15 kg/hm2 CaCO3)、C1Ca3(0.5%C+988.54 kg/hm2 CaCO3)、C2Ca2(1.0%C +1977.08 kg/hm2 CaCO3)、C3Cal (1.5%C+2965.61 kg/hm2 CaCO3). These following results obtained by experiment.The application of biochar and lime can significantly reduce the acidity of red soil. Compared with CK, the pH of the red soil increased 0.03-0.53 units by adding 2%,5% and 10% biochar, and the soil exchangeable acid decreases by 3.39%～ 77.27%. While, the lime increases soil pH by 0.34, decreases the exchangeable acid by 49.89%. The application of biochar can increase soil exchangeable ions content and soil fertility significantly. It also acts an important role on organic matter, total N, available P and K in the red soil. Biochar can improve the growth of soybean and increase soybean’s plant height, stem diameter, leaf area and biomass of soybean significantly.Results of the two consecutive seasons pot experiment shows that, the improvement of biochar on soil acidity and fertility acts out an aftereffect. Biochar still have a remarkable effect on reducing soil acidity after two seasons of soybean. Compared with the first season, treatments without biochar have a lower pH. On the contrary, treatments with different amounts of biochar improve their pH by 0.05-0.13 units. Meanwhile, the available P, available K, total N and the exchangeable cation of the soil are significantly improved by the biochar. For example, biochar improves the soil available K in the second season 15%～21% more than the first season. This may be due to the stability of the biochar, the alkaline substance and effective nutrients of the biochar release slowly in the soil, and the releasing process is gradually increases with time. Biochar also has a significant aftereffect on biomass, plant height, stem diameter and total K of soybean. But for the absorption of nitrogen and phosphorus, it has no obviously continuous improvement. That may be due to the low availability of nitrogen in biochar. Although it increases the amount of soil total nitrogen, but reduces the availability of nitrogen and the absorption of plants.The combination of biochar and lime can improve the pH and reduce the exchangeable acid in red soil. Effects of the mixed treatments are between single biochar and lime, among them, the treatment ClCa3 is the best one. Biochar mixed with lime increases soil organic matter and available K significantly, especially for treatment C3Cal, and mixed treatments also have a significant influence on total N and available P in soil. While, biochar combined with lime shows a positive effect on soil exchangeable cations, treatment ClCa3 increases exchangeable Na+and Ca2+ most, and treatment C3Cal increases exchangeable K+ and Mg2+ most. In terms of soybean yield and biomass, biochar combined with lime does not show obvious advantage. However, the combination of biochar and lime alleviates the nitrogen reduction caused by single application of biochar. It promotes the absorption of K too, particularly in treatment C3Cal. In general, the effect of combination of biochar and lime on the treatment of C3Cal is the most significant.The addition of biochar and lime has a significant effect on soil microbial community structure. Results show that the treatments added with lime and biochar have a higher content of Actinobacteria and a lower content of Acidobacteria. And with the increaseing of biochar, the content of Actinobacteria decreases, this is likely to be caused by the change of soil acidity from the lime and biochar. Biochar mixed with lime also has remarkable effects on soil microbial richness and diversity of species. Treatment ClCa3 and C3Cal improve the soil microbial diversity significantly. However, the single application of biochar or lime has little effect on the diversity of microorganism.