The Characteristics Of Biochars Pyrolyzed From Different Feedstocks and Their Amelioration Effects On Acid Soils.

Soil acidification has become the major concern of intensive agricultural systems in China. Thus, it is critical to develop new effective soil amendments to increase soil pH and soil fertility. In the present study, biochars derived from different types of feedstocks were pyrolyzed at 300 ^oC  or 500 ^oC for 2 h, respectively and their physico-chemical properties were characterized to evaluate their ability for soil improvement. The effects of four biochars (rape straw-, reed straw-, swine manure- and pineapple peel biochar) on the chemical and biochemical properties of two different acid soils (Psammaquent soil and Paleudalfs soil) were measured in soil incubation experiments.  Both pyrolysis temperature and feedstock affected the biochar characteristics. The pH, ash content (%), C (%), N (%), P (%), CEC, EC, BET, total and exchangeable base cations of biochars at 500 ^oC were higher than at 300 ^oC, while the yield, O (%) and H (%) of biochars were the opposite. Nutrient concentrations such as total K, P and total base cation and pH of swine manure-, pineapple peel- and rape biochars were higher than in reed straw biochar, which had the highest C concentrations. The SEM-EDS, XRD and FTIR analyses suggested both variations and similarities in their characteristics. The incubation experiments showed that pH, total C, total N, CEC, DOC, DON and exchangeable base cations in treated soils increased, while exchangeable Al decreased compared to the controls. The Psammaquent soil was more easily influenced by biochar addition than the Paleudalfs soil and biochar appeared more appropriate to correct the acidity in the Psammaquent soil than the Paleudalfs soil. The biochar derived from swine manure had the best effect on soil chemical and biochemical properties while the reed straw biochar had the lowest.