Efficacy of combined application of biochar,lime and humic acid in improving physical and chemical properties of degraded acidic red soil
Zhou Guo
Sheng Feng
Abstract：[Objective]Acidic red soil is widely distributed in southern China.It is characterized by high acidity,poor structure and low organic matter and nutrient availability.This study investigated the combined effects of biochar,lime and humic acid on improving physicochemical properties of such soils.[Method]The study was based on laboratory incubation experiments and compared sixteen combinations of the three amendments applied at different ratios into the soil.At the end of the experiment,we measured the physical and biochemical properties of the soil in each treatment.Comprehensive soil improvement effects were evaluated using grey correlation analysis,and economic efficiency was calculated via input-output ratio analysis.[Result]Combined application of biochar,lime and humic acid not only effectively reduced soil bulk density and acidity,and increased field water-holding capacity,but also elevated the contents of soil organic matter,ammonium-nitrogen,nitrate-nitrogen,available potassium and total phosphorus;it also improved soil aggregate stability.Among all treatments,applying 2.60 g/kg of biochar,1.20 g/kg of lime and 2.00 g/kg of humic acid yielded the optimal soil environment for crop growth.Compared with the untreated soil,this optimal treatment increased soil pH from 5.80 to 7.18,and raised soil porosity and field water-holding capacity by 54.55%and 34.27%,respectively.It also increased the content of＞0.25 mm water-stable aggregates,aggregate mean weight diameter and geometric mean diameter by 17.56%,26.03%and 39.58%,respectively,while reducing the aggregate fractal dimension by 0.17.In addition,this treatment increased soil organic matter content by 39.18%,and raised ammonium-nitrogen,nitrate-nitrogen,available potassium and total phosphorus contents by 23.89、33.10、63.08 mg/kg and 0.60 g/kg,respectively,relative to the control.[Conclusion]Combined application of biochar,lime and humic acid can effectively improve physicochemical properties of the degraded acidic red soil.Among all examined treatments,the combined application of 2.60 g/kg biochar,1.20 g/kg lime and 2.00 g/kg humic acid showed the best comprehensive improvement effect on soil physicochemical properties.
Keywords：red soilcompound amendmentorthogonal experimentsoil physical and chemical propertiessoil improvementgrey relational analysis
Publication Date：2026-08-31
Online Publishing Date：2026-09-12(First online date of this platform, not the publication date of the document)
Pages：10( 95-104 )