Effects of Biochar on Soil Humus in Farmland:A Meta Analysis
In order to quantify the influence degree of biochar on soil humus content,a meta-analysis of literature was used to integrate the changes of soil texture and pH,biochar pyrolysis temperature,application amount and duration,with soil humus content without adding biochar as a control.The results showed that adding biochar significantly increased humic acid and humin content in sand humus by 18.6％and 92.2％,respectively,compared with not adding biochar.The contents of humic acid in neutral and alkaline soils were increased by 12.5％and 13.7％respectively.The application of biochar with cracking temperature of 500-600℃ increased the contents of humic acid,fulvic acid and humin in soil by 22.6％,14.1％and 68.5％,respectively.Under the biochar application of 20-40 t/hm2,the contents of humic acid,fulvic acid and humin in soil were significantly increased by 23.7％,6.9％and 84.6％,respectively.The content of humic acid increased significantly in 3 months of biochar application,with an average increase of 29.5％.The increase gradually decreased from 3 months to 1 year,and gradually increased after 1 year.The humin content of biochar increased the most at 6 months,with an average of 72.2％.With the extension of biochar application time,the increase of humin content in soil decreased gradually.In summary,the application of biochar with a cracking temperature ranging from 500 to 600 ℃ exhibits significant short-term improvement effects on sandy and loam soils under neutral or alkaline conditions.Moreover,these effects gradually stabilize over time as the application period extends.
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