Acidity, water retention, and mechanical physical quality of a strongly acidic Ultisol amended with biochars derived from different feedstocks

Strongly acidic Ultisols in tropical and subtropical regions of China present one of the most important degraded soils. The improvement of soil quality for these soils is a key goal for sustainable agriculture. The purpose of this study is to evaluate the beneficial effects of biochar amendments on the soil acidity, plant available nutrient contents, and physical properties of a strongly acidic Ultisol. A Typic Plinthudult with low soil fertility and poor physical properties was amended by three biochars made from straw (SB), woodchips (WCB), and wastewater sludge (WSB) at the rate of 0, 2, 4, and 6 % biochar, respectively. After 180 days of incubation, the chemical, nutrient contents, water retention, consistency, tensile strength, and shear strength of biochar-amended soils were determined. Experimental results indicate that biochars significantly (p