Modified Phosphate Rock By γ-poly Glutamic Acid And Its Effects On The Growth Of Rapeseed Seedlings And Soil Properties

As well known,phosphorus is one of key and indispensable nutrients to plant growth. Additionally,phosphate is un-reproducible mineral resource and most of the arable lands across the world are seriously shortage of available phosphorus.Phosphorus deficiency is one of the most important limiting factor to either China or the world's agricultural production.The supply and demand of phosphorous fertilizer is and will be a prominent contradiction.So,how to make full use of the low-grade phosphate rocks,to accelerate their release from the low-grade phosphate rock and improve their effect to plant growth have the outstanding significance for the full using of China's phosphate rock source and the sustainable development of agriculture.Based on this point,a study was proposed and conducted aiming at probing the techniques how to efficiently and fully utilize the phosphorous in low-grade phosphate rock.In the study,three phosphate rocks(Morocco phosphate rock abbreviated as with MPR;North Carolina phosphate rock abbreviated as NPR;Guizhou phosphate rock abbreviated as GPR) was activated withγ-poly glutamic acid(γ- PGA) in different methods.We chose the best one of methods to prepare modified phosphate rocks.And we used the modified phosphate rocks to conduct the pot experiments of rapeseed seedling and the incubation test in three soils(red soil,yellow cinnamon soil and yellow brown soil).The main results and conclusions are followings:1.Preparation of modified phosphate rocksThree phosphate rocks(MPR,NPR,GPR) were separately mixed with four different concentrations ofγ- PGA and cultured different days to prepare modified phosphate rocks. The available P,water soluble P of modified phosphate rocks were analyzed to find the optimum method for modified phosphate rocks.The results showed that available P content of modified phosphate rocks was highest that phosphate rocks were cultured 7 days with 1:100 ofγ- PGA to phosphate rocks.So this method was the optimum method for modified phosphate rocks.Content of water soluble P of three modified phosphate rocks(MPR+PGA2,NPR+PGA2,GPR+PGA2) that were prepared in the optimum method increased separately 122.3,772,508 mg/kg than the corresponding phosphate rocks(MPR,NPR,GPR).2.Effects of modified phosphate rocks on the growth of rapeseed seedlingsThree modified phosphate rocks were used to conduct the pot experiments of rapeseed seedling in three soils(red soil,yellow cinnamon soil and yellow brown soil). The results showed that the rapeseed biomass of modified phosphate rock treatment was greater than that of other treatments in three soils.In red soil,content of the rapeseed biomass of three modified phosphate rocks(MPR+PGA,NPR+PGA,GPR+PGA) separately increased 295%,195%,14%than SP,and separately increased 149%,33%, 4%than corresponding phosphate rocks(MPR,NPR,GPR).In the three soils,the P content and the P uptake of the treatments added with modified phosphate rocks were higher than that of the treatments with phosphate rocks. Phosphate rocks modified withγ- PGA could significantly increase phosphorus uptake efficiency of rapeseed,and was also good for phosphorus utilization.Applying phosphate rocks could increase the content of soil available phosphorus after the PR.s being modified byγ- PGA.In red soil modified phosphate rocks had the most obvious effect of fertilizer, so modified phosphate rocks had better effect of fertilizer in lower fertility and acid soil.3.Effects of modified phosphate rocks on soil propertiesOn the incubation test,all the tested phosphate rocks can affect the chemical properties of three soils to some extent,with increasing the pH value,soluble phosphorus content and exchangeable Ca,Mg content,decreasing the exchangeable Al content.These changes in three soils followed the order:modified phosphate rock＞phosphate rock＞CK.To sum up,the phosphate rock power is a low-cost and rich-reserved natural mineral resource.Usingγ- PGA to activate phosphate rock may improve its availability and utilization efficiency.The result may provide the theoretical basis for usingγ- PGA as additives of phosphate rock.