Effects Of Biochar On Buffering Properties Of Soil In Tropical Area

Increasing soil nitrification caused by unreasonable agricultural management has become a major issue in the farmland soils in China.Soil quality would decrease induced by soil acidification,which lead to the decline of crop yield and quality.Biochar has been widely used for improving soil quality in recent years.A one-year incubation experiment with five treatments,N0(no biochar and nitrogen fertilizer),NB₀(no biochar),NB_0.025,NB_0.05and NB_0.1(2.5%,5%and 10%soil dry weight of biochar,respectively,and nitrogen fertilizer),was conducted to study the effects of biochar on soil buffering propertes for acid soils in tropical area in southern Yunnan.Acid sensitivity indictors with pH buffering capacity,exchange performance,soil organic carbon and so on,measured to determine the buffering propertes of the biochar-mixed soil with the soil samples collected on 30 days,90 days,180 days and360 days during the incubation period.Finally,multivariate statistical analysis applied to further study the mechanism of buffering propertes driven by biochar apllication.The results might provide scientific information for the management of soil and farmland ecosystem sustainable development of acid soil in tropical area of Yunnan province.The results showed that:(1)The pH buffering capacity of the three biochar treatments was significantly higher than that of the N0 and NB₀treatments on the 360 days after incubation,and the pH buffering capacity of 5%biochar was the highest in all treatmens.During the whole incubation period,the exchangeable acid and exchangeable Al³⁺of NB₀and three biochar treatments were significantly higher than that of N0 treatment,however there was no difference among the other four treatments.(2)The pH value decreased in the all treatments during the incubation period.At the end of incubation,the pH value of NB₀and three biochar treatments decreased by1.84?2.38 pH units,compared with that of N0 treatment.The pH value decreased by0.61?0.91 pH units with NB₀and three biochar treatments on the 360 days after culture.On the 180 days after incubation,there was no difference in pH value between N0,NB₀,2.5%and 10%biochar treatments,and the pH value of 5%biochar treatment was significantly higher than other four treatments.At the end of incubation,there was no difference in pH value between 5%biochar treatment and NB₀treatment,while the pH value of 2.5%and 10%biochar treatment decreased significantly compared with NB₀treatment.(3)Biochar had obvious effect on maintaining the cation exchange capacity.At the end of incubation,the cation exchange capacity did not decrease in the three biochar treatments,compared with the treatments of N0 and NB₀.Compared with N0and NB₀treatments,exchangeable Ca²⁺increased and exchangeable Mg²⁺,K⁺and Na⁺decreased in the biochar treatments.During 30?180 days,the total amount of exchangeable base of biochar treatments was significantly lower than that of N0 and NB₀treatments,however,the difference among the all treatments was not significant after 360 days culture.(4)The pH value,exchangeable Ca²⁺,exchangeable Mg²⁺and organic carbon were the important factors affecting pH buffering capacity of the studied soil.There were significant positive correlation between pH,organic carbon and pH buffering capacity,while significant negative correlation found between the exchangeable Ca²⁺,exchangeable Mg²⁺and pH buffering capacity.The results indicated whether biochar is added or not,the treatment of applying nitrogen fertilizer shows a trend of acidification with the extension of incubation time.Biochar can significantly reduce exchangeable acid,especially exchangeable Al³⁺,but it is not ideal for improving soil pH,pH buffering capacity and exchangeable base ion.