海南热带土壤对磷的吸附特性与施磷量的关系

RELATIONSHIP BETWEEN PHOSPHORUS SORPTION CHARACTERISTICS AND PHOSPHATE FERTILIZER APPLICATION RATE IN TROPICAL SOILS OF HAINAN ISLAND

对海南岛主要类型土壤磷的等温吸附曲线、“磷肥指标”的测定和盆栽试验结果表明:海南岛热带土壤对磷的最大吸附量差异很大,吸附容量愈大,其“标准需磷量”愈高,但是最大吸附量与标准需磷量的比率,则与吸附系数有关;各类土壤施磷量与土壤有效磷提取量呈直线相关,其斜率“b”称为“磷肥指标”,“b”愈大,磷肥的有效程度愈低,要达到一定有效磷水平所需要的施磷量也愈大;各类土壤盆栽花生最高生物量(干重)所对应的施磷量与两种方法预测的土壤需磷量相近,证明应用该两种方法预测热带土壤的需磷量是可行的;缺磷土壤初时的施磷量必须达到一定水平才显肥效。

The phosphorus sorption isotherm and the“phosphate fertilizer index”were det- ermined for the key soil types of Hainan Island and a pot culture experiment was laid out accordingly The results are as follows:The maximum phosphorus sorption rates are remarkably different in the tropical soils of Hainan Island。The greater the sorption capacity,the higher the“normal phosphorus fertilizer requirement”.However,the ratio of the maximum sorption rate to the“normal phosphorus fertilizer requirement” is related to the adsorption coefficient,phosphate application rates have a linear rel- ation to the extraction amount of available phosphorus in various soil types,with the slope“b”named as“phosphate fertilizer index”.The greater the value of“b”,the lower the availability of phosphorus,and the much phosphate fertilizer is needed to reach a certain level of available phosphorus.The phosphorus application rate at wh- ich the maximum biomass(D.M)of peanut was obtained in the pot culture from ea- ch soil type is similar to that predicted by using“phosphate fertilizer index”and ad- sorption isotherm.This result indicates that applying these two methods to estimate the rate of phosphorus application in tropical soils is feasible,phosphate fertilizer applic- ation is effective only when the initial rate applied to the p-deficient soils reaches a certain level.