有机酸对土壤无机态磷转化和速效磷的影响

土壤有效磷含量低是影响作物生产的重要限制因素之一.作物根分泌活化难溶性磷的有机酸对改善其磷素营养具有重要意义.采用张守敬和Jackson无机磷分级方法,以湖北省3种pH值土壤为材料,加入不同磷源和有机酸,经过室温培养后,测定速效磷含量和无机磷组分的变化.结果表明:施磷显著提高了土壤中速效磷含量,中性土、酸性土Fe-P和Al-P含量大幅上升, Fe-P占增加量的50%以上,而碱性土Ca-P含量显著增加.加施有机酸使中性土速效磷含量增多,除苹果酸处理的变幅较小外,草酸和柠檬酸的加入速效磷显著增加.由于有机酸的作用,中性土Al-P含量下降,Ca-P含量上升,变幅大小依次为草酸＞柠檬酸＞苹果酸;酸性土中Al-P含量呈下降趋势,碱性土中Ca-P含量有不同程度的减少,3种土壤中O-P含量均有所增加.说明有机酸活化的磷主要来源于中性土和酸性土Al-P、Fe-P及碱性土Ca-P中的磷,同时有机酸能够促进土壤中闭蓄态磷(O-P)的形成与积累.

Effect of organic acids on inorganic phosphorus transformation in soils and its readily available phosphate

Low of available phosphorous is one of the major limitations to crop production. Mobilization of insoluble phosphates by root exudates plays an important role in improving P nutrition of crops. Three types of soils collected from Hubei province were tested to analyze the changes of inorganic phosphorus fractions and available phosphorous after incubated with addition of various organic acids and different phosphorus sources. The results indicated that P added as fertilizer increased available phosphorous in all soils. On soils of pH4.6 and pH6.8 the fertilized phosphorus was transformed into Fe-P and Al-P mainly. However, on soil of pH8.3 the fertilized phosphorus significant increased content of Ca-P. Organic acids had significant influence on available phosphorous except malic acid. Application of organic acids decreased the content of Al-P and increased the content of Ca-P in neutral soil, in the order of Oxalic acid > Citric acid > Malic acid. Phosphorus was activated by organic acid mostly from the fractions of Al-P and Fe-P in acid soil and neutral soil, but fractions of Ca-P in alkali soil, at the same time, organic acid accelerated formation and accumulation of O-P in the three soils.