Leaching Of Phosphorus From The Acidified Purple Soil Under The Condition Of Different Nutrient Management

Purple soil accounts for 69.2% of the area of cultivated land, and the form of acidification is becoming increasingly serious due the acid rain as well as long term application of chemical fertilizer. Acidity changes soil physical and chemical properties comparing with neutral or alkaline soils of the same group. In order to understand the leaching of phosphorus from acidified purple soils, field experiments in Longwanggou and pot experiments in the greenhouse were conducted. The results of our research showed as follow:1) The leaching risk of phosphorus from acidified purple soils was bigger under the condition of mustard tuber-rice crop rotation (0.019-2.687ug/ml) than mustard tuber-corn crop rotation (0.019-0.289ug/ml); and the risk was significantly greater in rice season (0.091-2.687ug/ml) than maize season, it was greater in corn season (0.104-0.289ug/ml) than mustard tuber season (0.019-0.239ug/ml); the leaching risk of phosphorus was significantly higher under organic fertilizer treatments in rice season (0.091～2.687ug/ml)than chemical fertilizer treatments(0.180～1.102ug/ml). In mustard tuber season, the leaching concentration of total phosphorus, particulate phosphorus and orthophosphate under chemical fertilizer treatments was lowest in the beginning of the enlargement, highest in vegetative growth;however, the leaching concentration of its dissolved phosphorus was in a relatively stable state from the beginning of the enlargement under organic fertilizer (manure) treatments; the leaching risk of the rest of phosphorus forms was a minimum in tumor morphology stem growth. In corn season, the peak leaching concentration of total phosphorus and particulate phosphorus under chemical fertilizer treatments emerged at the elongation and filling stages, and that of its dissolved phosphorus and orthophosphate was mainly at 7-8 leaf stage; but under organic fertilizer (manure) treatments, the leaching concentration of its total phosphorus and particulate phosphorus was in small ups and downs throughout the growing period, and the peak leaching concentration of its dissolved phosphorus and orthophosphate was mainly at 7-8 leaf stage. In rice season, under chemical fertilizer treatments, the leaching concentration of its total phosphorus and particulate phosphorus was lower at the elongation stage, and the main peak value was at the heading stage; at the same time, its dissolved phosphorus and orthophosphate also appeared the leaching peaks; under organic fertilizer (manure) treatments, the leaching concentration of its total phosphorus and particulate phosphorus was lowest at the tillering-elongation stage, in the meantime, the concentration of its dissolved phosphorus and orthophosphate leaching appeared a "trough"; there was the greater leaching risk of its total phosphorus and particulate phosphorus during heading and the filling stage.2) The leaching amount of phosphorus from acidified purple soil itself was high in this test, and with increasing calcium superphosphate, the leaching amount of soil phosphorus from acidified purple soil (dry land) was a rise-fall-(stable) trend, but there was not an effect on the cumulative leaching concentration of phosphorus in rice season; and with increasing amounts of organic fertilizer, the leaching amount of phosphorus was a upward (stable)-downward trend. In rice season, the leaching risk of phosphorus was higher under organic fertilizer treatments than chemical fertilizer treatments.3)The main leaching form of phosphorus from acidified purple soil was particulate phosphorus; and the most important leaching form of dissolved phosphorus from acidified purple soil (dry land) was dissolved organic phosphorus; orthophosphate was the main leaching form of dissolved phosphorus under organic fertilizer treatments in rice season, but if applied calcium superphosphate, dissolved organic phosphorus was its main form.4) Compared with the control, fertilizer application amount did not significantly affect microbial biomass carbon and acid phosphatase activity in acidified purple soil; but the organic fertilizer could improve the content of soil microbial biomass carbon; and the content of microbial biomass carbon and acid phosphatase activity were greatly influenced by the cultivation of different crops; then the correlation analysis showed that acid phosphatase activity and soil microbial biomass carbon play a certain role in potential leaching of phosphorus from acidified purple soil.5) In this test, the highest utilization rate of phosphorus in acidified purple soil (dry land) was about 24.7%; and it was about 7.7% under calcium superphosphate treatments in rice season, but the utilization rate of organic phosphorus was higher, between 47.2%～81.6%; under similar nutrient condition, the phosphorus uptake of crop was lower under organic fertilizer treatments than calcium superphosphate treatments, it increased phosphorus residues in the soil.6) In this study, considering the level of phosphorus amount, plant dry weight, phosphorus absorption and utilization, reducing phosphorus pollution to the environment and saving phosphorus resource in acidified purple soil, appropriate fertilizer application level for mustard tuber was 35kg/hm2 calcium superphosphate or no; suitable fertilizer application level was 87kg/hm2 calcium superphosphate in maize season; and less calcium superphosphate and appropriate amount of nitrogen was more appropriate in rice season.7) Effective nutrient of acidified purple soil in Longwanggou could not be release, because of its structure factors and so on, the higher yield of mustard tuber mainly depended on the applied NPK fertilizers; so optimized fertilization for mustard tuber in Longwanggou play an important role in controlling agricultural non-point source pollution, and 4DAgro Model could guide fertilization.