红壤磷素有效性衰减过程及磷素农学与环境学指标比较研究

摘要

[目的]研究红壤中磷素有效性衰减的关键过程及其与施肥量的关系,明确农学与环境学土壤有效磷指标之间的数学关系.[方法]以亚热带红壤为试验材料,通过人工施肥和室内恒温( 25℃)培养试验,应用01sen (OP)、Bray-1( BP)、Mehlich-3 (BP)3种农学方法和蒸馏水(HP)、CaCl2( CP)两种环境学方法,分别在1h、3h、12 h、24 h、3d、6d、9d、15 d、30 d、60 d用新鲜土样测定土壤有效磷以及磷吸附指数(PSI)的动态变化.[结果]红壤磷素有效性衰减过程存在明显的临界期,变化范围为0.1-18.7 h,此前衰减速度很快,之后明显变慢.施肥量对临界期有显著影响,其中OP、BP、MP的临界期随施肥量增加呈线性延长的趋势,而HP、CP临界期随施肥量的增加呈幂函数延长趋势.环境学与农学指标之间表现为非线性关系,存在明显的“突变点”,据此可求算出红壤磷素迁移的环境风险临界值,其中根据CP变化求算的OP、BP和MP临界值分别为49.97、91.07和30.54 mg·kg-1,根据HP变化求算的OP、BP和MP临界值分别为60.78、82.74和39.65 mg·kg-1.磷吸附指数(PSI)随施肥量的变化范围为17.92-26.29,OP的环境风险临界值对应PSI为23.46.[结论]磷素有效性在红壤中的衰减过程存在明显的临界期,施肥量越高临界期越长,因此向环境迁移的风险就越大.土壤有效磷的环境学指标与农学指标存在非线性关系,据此可以确定出土壤磷素迁移的环境风险临界值.供试红壤的01sen-P含量临界值为50-60 mg·kg-1,PSI的环境风险临界值为23.46.%[ Objective] This study is to probe the key declining process of soil available phosphorus (SAP) and its relationship with P fertilizer application rate in red soil, and to verify the mathematical relationships among soil available P indexes in agronomy and environment. [Method] An laboratory incubation experiment was conducted with artificial fertilization and stable temperature of 25 "C using the material of red soil collected from subtropical area. The dynamic process of SAP was studied through testing SAP and phosphorus sorption index (PSI) in fresh soil samples in I h, 3 h, 12 h, 24 h, 3 d, 6 d, 9 d. 15 d, 30 d, and 60 d after fertilizer application into soil. Two types of test methods including Olsen- (OP), Bray HBP), and Mehlich 3- (MP) extraction methods (agronomic type) and distilled water (HP) and 0.01M CaCl2 (CP) extraction methods (environmental type) were used. ' [ Result ] There was an obvious critical time (