The Immobilization Effects And Mechanism Analysis Of Mineral Soil Conditioner On Nitrogen And Phosphorus

The loss of nitrogen and phosphorus in soil is not only an important issue in the development of agricultural production,but also the main source of agricultural non-point source pollution.Their loss makes the use of chemical fertilizer increased and the efficiency of utilization of chemical fertilizer decreased,besides,caused water environmental pollution and water eutrophication,which is a key problem that affects and restricts the sustainable development of the country and the region.At present,all countries in the world are committed to study the techniques to improve the utilization efficiency of nitrogen and phosphorus and reduce the loss of nitrogen and phosphorus in soil.Since 18th CPC National Congress,many rules and measures have been implemented on the policy of ecological civilization and environmental protection,and the coordinated development of the economic and agricultural environment has been achieved through the regulation of macroeconomic environmental policies.In this paper,a mineral soil conditioner is comprised with potassium feldspar which is a kind of natural potassium rich aluminosilicate mineral as main material,calcium magnesium carbonate minerals and calcium sulphate as auxiliary materials preparing with high temperature activation technology.The mineral soil conditioner can be used to supplement the elements and inhibit soil acidification due to long-term weathering of soil caused soil desilication and aluminizing to form ferralsol and mineral elements deficiency considering the characteristics of soil and climatic of tropical and subtropical regions.At the same time,it also aims to improve the soil quality of the ferralsol,restore the original ecological nature of the soil and improve the utilization efficiency of soil nitrogen and phosphorus.The mechanisms and results are analyzed through field test,batch experiments,Zeta potential test,XRD,XPS,ATR-FTIR,and FactSage thermochemical calculation software.On the other hand,the adsorption mechanism of inorganic phosphorus and organophosphorus in different soil minerals,such as gibbsite,kaolinite,illite and montmorillonite,is calculated and analyzed by using the quantum chemical about density functional theory to provide a theoretical basis for improving the utilization efficiency of soil phosphorus further.It is also provides a scientific basis for utilization of natural minerals as agricultural resources.On on hand,the mineral soil conditioner applied in ferralsol can improve the utilization efficiency of nitrogen in soil and crop.By comparing three kinds of soil amendments,such as lime,bioactive carbon and mineral soil conditioner,the results showed that the application of mineral soil conditioner was 5.63%¹5.48%higher than that of bioactive carbon and lime.Compared with the control check,the application of mineral soil conditioner on the intensity of xylem sap and the export intensity of nitrogen increased by 37.33%³9.85%and31.40%⁵1.20%at different growth stages of rice.The mineral soil conditioner has a tendency to transform the kaolinite to illite by spontaneous endothermic reaction under the standard atmospheric pressure at room temperature due to the existence of active H₄SiO₄ and K⁺through the analysis of FactSage 6.1 thermochemical calculation software,XRD and ATR-FTIR.On the other hand,the mineral soil conditioner applied in ferralsol can improve the utilization efficiency of phosphorus and soil physical and chemical properties.To further explore the mechanisms through XRD,XPS,ART-FTIR and FactSage 6.1 thermochemical calculation software,it is found that the active component of mineral soil conditioner can make the kaolinite in ferralsol gradually transformed into illite with two steps through spontaneous endothermic reaction.The mineral soil conditioner has the significant effect on improvement of phosphorus utilization efficiency and clay mineral transformation in the application of M2?975 kg/ha?.Besides,the phosphate adsorption capacity of aluminum oxide is stronger than that of ferric oxide.From the above analysis,the density functional theory study shows that the adsorption intensity of soil minerals on potassium dihydrogen phosphate is montmorillonite>illite>kaolinite>gibbsite.The adsorption intensity of soil minerals on myo-inositol hexaphosphate is montmorillonite>illite>kaolinite>gibbsite.In addition,the adsorption experimental results show that the maximum adsorption capacity of soil mineral to potassium dihydrogen phosphate and the values of adsorption distribution coefficient are:montmorillonite>illite>kaolinite>gibbsite>goethite.The maximum adsorption capacity and adsorption distribution coefficient of different soil minerals for myo-inositol hexaphosphate are:montmorillonite>illite>kaolinite>gibbsite>goethite.Besides,the adsorption capacity of myo-inositol hexaphosphate is stronger than that of potassium dihydrogen phosphate when the competitive adsorption existed in soil mineral.