酸性土壤磷分级新方法建立与生物学评价

DEVELOPMENT OF A NEW PHOSPHORUS FRACTIONATION SCHEME IN ACID SOILS AND BIOLOGICAL EVALUATION

土壤磷分级方法可用于估算土壤有效磷数量、不同土壤磷组分库数量及其对土壤有效磷的补充能力。以云南赤红壤、黄红壤及湖北棕红壤为供试材料,运用张守敬方法、蒋柏藩方法及本文提出的新方法,对三种酸性土壤和其石灰改良后的土壤磷进行分级研究,探讨石灰改良对酸性土壤磷组分数量及其生物有效性的影响。结果表明:Ca2-P、Al-P和Fe-P是酸性土壤主要的有效磷源,O-P(闭蓄态磷)也是潜在有效磷源,土壤中活性有机磷库相对比较稳定,可转化为高活性有效磷源供植物吸收利用。与两种经典磷分级方法相比,新方法将O-P划分为O-Al-P和O-Fe-P,O-Fe-P较好地反映了石灰处理与对照之间的土壤磷植物有效性差异。

Phosphorous fractionation is a method developed to estimate sizes of readily soil available P pool, and soil P subpools and their ability to replenish the available P pool. Three types of acid soil （laterite red soil, yellow red soil and brown red soil）, of which the first two were sampled from Yunnan Province and the third one was sampled from Hubei Province, were used in pot experiment under a rain-shelter condition to investigate the effect of lime amendment on P fractions and their bioavailability by plant of broad bean. A new phosphorus fractionation scheme was developed and used to study P bioavailability in the tested soils compared with the two typical soil P fractionation schemes, Chang-Jackson on acid soil and Jiang-Gu on calcareous soils. The new phosphorus fractionation scheme used a series of sequential extractants, such as 0.25 mol L^-1NaHCO3,1 h （for Ca2-P）,0.5 mol L-1^NH4F （pH8.5）,1 h （for Al-P）,0.7 mol L^-1NaClO,pH 8.05,85℃ water bath 30 min （for Org-P）,0.1 mol L^-1 NaOH-0.1Na2CO3,4 h （for Fe-P）,1 mol L^-1NaOH,85℃ water bath 1 h （for O-Al-P）,0.3 mol L-1^Na-eitrate-0.5 g Na2S2O4 -0.5 mol L-^1NaOH,80℃ water bath 15 min （for O-Fe-P）,0.25 mol L-^1H2SO4, 1 h （for Ca10-P）. Results showed that Ca2-P, Al-P and Fe-P were the main available P sources in acid soils. O-P was potentially available phosphorus source, which could be subdivided into O-Al-P and O-Fe-P with the new phosphorus fraetionation scheme,and the latter reflected difference between CK and lime treatment in plant availability. The size of the labile organic fraction was relatively invariable and could be transformed into a highly available P source to plant. Further study may be needed on extraetant for labile organic phosphorus in determining soil P availability in acid soils.