OPTIMUM BIOCHAR APPLICATION RATE FOR IMPROVING SOIL MOISTURE CHARACTERISTICS

摘要

Water movement and storage in soils are crucial for successful intensification of agriculture and maintaining productivity in the face of changing climate. Previous studies have shown biochar to be a natural porous material with potential to be used in maintaining soil moisture. Its application, especially in sandy soils can improve total soil porosity, pore size distribution and soil aggregation thereby increasing total water retained as well as maintain this water in the soil for a long time. However, there is little known about the optimum rate of biochar application in sandy soils for moisture improvement. The cost of biochar production varies from US$300 to $7000 per tonne and most studies to date used relatively high application rates of biochar. At such high application rates, the cost may not lead to a return on investment. This study aims to assess the optimum rate of biochar application as well as to evaluate the potential of biochar particle size in affecting this rate. An extensive meta-analysis was performed on published literature data to quantify the relationship between biochar characteristics and soil moisture properties. The literature data spans across a wide range of feedstock, pyrolysis condition, soil texture and experimental conditions. Out of a total of 150 published studies, 42 articles providing sufficient amount of reliable data on biochar-soil moisture effects were selected. These studies covered; 51 feedstock, 16 pyrolysis temperatures, 20 particle size ranges, 12 soil textural classes and 45 rates of biochar application. The meta-analysis results confirmed that biochar particle size, surface area, feedstock, porosity and carbon content are important factors to consider when using biochar as a material for improving soil moisture content and identified relative importance of different parameters.