提取剂和土水比对旱耕地土壤无机和有机磷的提取效应

比较了O lsen(0.5 mol L-1NaHCO3)和B ray-1(0.03 mol L-1NH4F-0.025 mol L-1HC l)提取剂土水比1∶4和1∶20(W/V),对我国5种类型旱耕地土壤(pHKC l3.3~7.4)无机磷(Pi)和有机磷(Po)及外加正磷酸盐态无机磷的提取效应。结果表明,以O lsen提取剂土水比1∶20对土壤Pi和Po的提取效果最佳,其测定结果是评价土壤磷素供应能力(有效磷)和活性有机磷含量较为适宜的指标。测定的土壤大多数(占60%)磷素供应能力较差(O lsen-Pi为4.2~14.0mg kg-1),应适当加强其磷素的投入。测定的土壤活性有机磷(O lsen-PO)含量为1.4~37.9 mg kg-1,占土壤全磷的0.2%~15.8%,大多数(75%)土壤占1%~6%。采用O lsen提取剂时土壤外加Pi的固定率随土水比减小而增高,当土水比1∶4提取时,酸性和强酸性(pHKC l3.3~5.5)土壤对外加Pi的固定率达40%~86%,据此推测实际田间条件下土壤对外加Pi的固定率更大。表明酸性和强酸性旱耕地土壤对外加Pi具有强烈的固定作用。

Influence of Extractant Types and Soil to Solution Ratios on the Extraction of Inorganic and Organic Phosphorus in Upland Soils of China

Extractable inorganic and organic P(Pi and Po) corncentrations and the adsorption ratios of added inorganic P(APi) in five types of upland soils in China were compared by using Olsen and Bray-1 extractants at soil to solution ratios of 1∶4 and 1∶20(w/v).In the 12 soil(pH_(KCl) 3.3-7.4) tested,relationships between extractable Pi or Po by Olsen extractant at soil to solution ratio of 1∶4 and 1:20 were linear(r = 0.9112~(**) or 0.9794~(**)).However there were not significant correlations between Pi or APi extractable by Bray-1 extractant at 1∶4 and 1∶20.All of the results showed that extractable Pi and Po by Olsen extractant at 1∶20 were the most suitable for assessing available Pi and labile Po in soils in China.In most(60%) of the soils,Olsen-Pi concentrations were very low(4.2 to14.0 mg P kg~(-1) soil).In the used soils,Olsen-Po concentrations ranged from 1.4 to 37.9 mg P kg~(-1) soil.It accounted for 0.2-15.8% of the soil total P.In most(75%) of the soils,Olsen-Po accounted for 1-6% of the soil total P.The values of AP_i extractable by Olsen extractant at soil to solution ratio of 1∶4 were much larger(11% to 51%) than those at 1∶20.It illustrated that the smaller ratios of soil to solution,the values of AP_i extractable by Olsen extractant were larger.For acidic soil(soil 1-8,pH_(KCl)3.3-5.5),the values of AP_i extractable by Olsen extractant at 1∶4 ranged from 40% to 86%.According to the results,the APi of acidic soils in field conditions were larger than those extractable by Olsen extractant at 1∶4.