Structural Composition And Chemical Activity Of Three Phosphate Rocks And Their Dissolution Kinetics In Paddy Soils

The research about dissolution nature of three PRs with various activities and interference of different environment factor is done. There are four trials designed, which are extract test with 2% citric acid, dissolving kinetics experiment in buffering solution of NH4OAC(pH4.8),and two experiments to question the dissolution kinetics of PRs added in Paddy soils. Then ,the author analyze the fitness between PR's dissolution and Elovich equation and Mitscherlich equation .Total and citric phosphate of KPR'> GPR' > WPR's equally.During the experiment of successive eight times extraction, the ability of incessancy providing phosphorus is very nice on KPR and GPR, however, it holds a little higher lever of phosphorus concentration, then declines quickly. In acid solution of NH4OAC(pH4.8) at low solid solution ratio, the order of release amount for the three PR is that GPR > KPR > WPR, while, at the high lever, it is that KPR>GPR>WPR.During the dissolution of PRs in paddy soil, the interference is double. At the same temperature, the relation of pH and dissolving amount isnegative, more lower is pH, more higher is dissolving amount ; at the same pH, the one is positive. And the fertilization status of soils also affect the dissolution at a certain degree, as temperature rises , dissolving amount rises. The amount of PR dissolution doesn't grow added to the soil(NK) absence of phosphorus extremely, but it is stronger than the former, added to the soil(NPK) non-absence of phosphorus. Commonly, the dissolution rate of PRs in soils isn't large. Even if in the best conditions , it 's only 20 percent of total phosphate. The transfer of Phosphorus in soil solution to plant available varies from the properties of the soils. According to the data of incubation experiments, in the paddy soil, the activity of WPR is the strongest, following KPR, and the last is GPR. Elovich equation and Mitsherlich equation may describe the kinetics procedure of dissolution in soils. Elovich equation is suitable to describe the factor very much, such as temperature and pH. Its relationship is significant or dearly significant. In this experiment, the fitness for Mitsherlich equation to data of dissolution kinetics data few lower than Elovich equation relatively.