螯合剂对不同磷源的释磷效应研究

了解螯合剂等肥料增效物质对不同磷源磷素释放效果的影响,可为全面认识螯合剂对磷素释放后在液相中的赋存形态提供依据。选取两种不同类型的土壤(酸性红壤和石灰性土壤)和五种磷酸盐矿物磷酸氢二钙(DCP)、磷酸八钙(OCP)、羟基磷灰石(FA)、铝磷(Al-P)、铁磷(Fe-P)]作为磷源,通过实验室化学浸提试验,研究了螯合剂(EDTA-2Na)对不同磷源的磷素释放率和释放形态的影响。结果表明:(1)螯合剂对不同磷源磷素的释放均具有促进作用,且不同磷源的磷素释放率均随螯合剂浓度的增加而显著增加;(2)随着螯合剂浓度的增加,酸性红壤和石灰性土壤浸提液中钼酸盐非反应磷占总磷的比值均显著下降,DCP、OCP、FA浸提液中钼酸盐非反应磷占总磷的比例则显著增加,而Al-P和Fe-P浸提液中钼酸盐非反应磷占总磷的比例变化不大;(3)浸提液中的磷只有极少量以游离态磷酸根的形态存在,3.00 g·L~(-1)的DETA-2Na处理下,DCP、Al-P和Fe-P浸提液中游离态的磷酸根占总磷含量的比例分别仅为0.43%、1.12%、0.63%;(4)螯合剂对不同磷源磷素释放后,溶液中总磷与相应金属离子的摩尔比基本不变。

Effects of chelating agents on phosphorus release from different phosphorus sources

To study the effects of fertilizer synergists, such as chelating agents, on the release effect of different phosphorus sources, can provide a comprehensive understanding of the form of the released phosphorus in liquid phase by the chelating agent.Two different types of soils (acid red soil and calcareous soil) and five kinds of mineral phosphate (calcium hydrogen phosphate (DCP), octacalcium phosphate (OCP), hydroxyapatite (FA), aluminum phosphate (Al-P), iron phosphate (Fe-P)) as phosphorus sources were selected. Then, the effect of the chelating agent (EDTA-2Na) on the phosphorus release rate and release form from different phosphorus sources were studied through a laboratory chemical extraction test. The results showed that:(1) Chelating agents could promote the release of phosphorus from different phosphorus sources, and the phosphorus release rate increased significantly with the increase of chelating agent concentration. (2) With the increase of chelating agent concentration, the ratio of molybdate unreactive phosphorus (MUP) to total phosphorus (TP) in the extracts decreased significantly in acid red soil and calcareous soil, whereas it significantly increased in three kinds of Ca-P compounds and did not change significantly in Al-P and Fe-P compound treatments. (3) Only a small amount of phosphorus in the extracts existed in the form of free phosphate.Under the EDTA-2Na treatment of 3.00 g·L^-1, the ratio of free phosphate to total phosphorus in the extracts of DCP, Al-P, and Fe-P was only 0.43%, 1.12%, and 0.63%, respectively. (4) The molar ratio of TP to the corresponding metal ions in the solution was almost unchanged after the release of phosphorus from different phosphorus sources.