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Characteristics of crop straw-decayed products and their ameliorating effects on an acidic Ultisol

ABSTRACT The purpose of this study was to examine the characteristics of four crop straw decayed products (SDPs) and their ameliorating effects on an acidic Ultisol. The straws of peanut, canola, rice and pea were decayed for 150 d to obtain decayed products. The Ultisol collected from Jiangxi province was incubated with these SDPs for 30 d. Then, soil pH and soil pH buffering capacity (pHBC) were measured and a simulated acidification experiment was carried out. The results showed that the SDPs had high pH and contained carbonate, organic anions and nutrients of N, P, Ca and Mg. Applying the SDPs increased not only soil pH but also soil pHBC, and thus the resistance of the soil to acidification significantly (p < 0.05). The pea straw decayed product showed the greatest effect on soil pHBC, followed by peanut straw decayed product. The incorporation of the SDPs slowed down soil acidification and reduced the concentration of soil soluble Al and decreased soil exchangeable Al during simulated soil acidification. Dissolution of carbonate and protonation of organic anions on the surface of solid organic matter were the main mechanisms for increasing soil pH and soil pHBC by the SDPs.