根分泌物对活化土壤中难溶性磷的作用

土壤大部分磷以难溶性磷形式存在,是影响作物生产的重要限制因素之一。作物根分泌物活化难溶性磷的能力对改善其磷素营养具有重要意义。采用室内培养方法,研究3种土壤不同磷(KH2PO4)处理后有效磷动态变化情况;同时将不同玉米基因型分别置于全磷和低磷的营养液中生长15 d后,收集根系分泌物,然后加入预先采用磷酸钙和磷酸铝处理并已培养95 d的土壤样品中进行试验。不同磷处理研究结果表明,所有施磷处理短期内速效磷含量急剧上升,并随培养时间推移不断下降,60 d后趋于稳定。酸性土对磷的吸附和固定作用较强,磷处理后有效磷增加量显著小于中性土、碱性土。土壤加根系分泌物的试验表明,磷酸钙和磷酸铝有效磷的含量较对照有所提高,其中加入耐低磷基因型M02低磷根系分泌物浸提的土壤有效磷含量显著高于去离子水的浸提量,且根系分泌物对磷酸铝的活化能力大于磷酸钙。

Effects of Root Exudates on Mobilizing Insoluble Phosphate in Soils

Low phosphate availability is one of the major limitations to crop production.Organic acids are a principal component of root exudates and have been hypothesized by many authors to be involved in the mobilization of nutrients within the rhizosphere.Mobilization of insoluble phosphates by root exudates plays an important role in improving P nutrition of crops.The effect of different phosphorus level on dynamic of available phophorus in soils had been studied.At the same time,two maize inbred lines with different tolerance to low-P stress were grown for 15 days in nutrient solution with different phosphorus treatment.The root exudates were collected and added into the three types of soil which had incubated for 95 days.The results showed that the available phosphorus content quickly increased by application of different phsphate,and then constantly decreased by time,and were steady after 60 day;and the available phosphorus from acid soil is significant lower than alkali soil and neutral soil.The soil available phosphorus content was extracted by the root exudates of M02 collected under low phosphorus condition significant pronounced with the addition of insoluble phosphate to the deionized soil;and AlPO4 mobilization by root exudates was significantly higher than Ca3(PO4)2.