The Study On Adsorption-desorption Of Organic And Inorgani Phosphorus In Paddy Soils

In order to reveal the behavior characteristics of phosphorus in soil, provide a scientific basis for environment friendly use of phosphorus firtilizer .The adsorption-desorption characteristics of three typical paddy soils, Hongrang paddy soil (derived from red earth), Huangnitu paddy soil (derived from Ferric-accumulic stagnic anthrosols) and Chaoshatu paddy soil (derived from fluvo-aquci soil) to inorganic phosphorus (KH2PO4), organic phosphorus (Phytic acid) and phosphorus in poultry manure were studied in this paper.The main results showed that:1. The inorganic phosphorus (KH2PO4) and organic phosphorus (phytic acid) adsorption characteristics of three paddy soils were similar:the maximum adsorption capacity of soils was in the order of Hongrang paddy soil > Huangnitu paddy soil > chaoshatu paddy soil, and the organic phosphorus adsorption of each paddy soil was greater than the inorganic phosphorus adsorption.2. The inorganic and organic P adsorption of three paddy soils was well fitted by Langmuir equation, Freundlich equation and Temkin equation ,comparatively the Langmuir equation was better to fit the inorganic phosphorus adsorption, while the Temkin equation was better to fit the organic phosphorus adsorption.3. Desorption capacity of each paddy soil were exponentially increased with the adsorption capacity. The desorption P of the Chaoshatu paddy soil with a lighter texture was greater but its adsorption P was lower; while for Hongrang paddy soil with a heavy texture, its adsorption P was higher but its desorption P was lower. This indicated that the mechanism of P adsorption and desorption would be different for the different soils.4. The organic and inorganic P adsorption of three paddy soils to poultry manure was significantly lower than to a single inorganic P (KH2PO4) and to a single organic P (phytic acid). It was probably associated with the presence of competitive adsorption when the poultry manure added in the soils.5. Low-molecular-weight organic acids had an obvious influence on the phosphorus adsorption. Among four organic acids, the citric acid reduced the P adsorption greatest, then the oxalic acid, the tartaric acid, and the acetic acid. For the same organic acid, the P adsorption capacity was decreased with the increase of organic acid concentration. The pH value in solution had little effect on the adsorption of phosphorus, and the phosphorus adsorption capacity of the paddy soils was impacted by the buffer solution and generally increased with the increase of buffer solution concentration.