Effects Of Combined Application Of Phosphorus Fertilizer With Organic Manure On Soil Phosphorus Transformation And Phosphorus Absorption And Utilization By Rice Plants Under Simulated Condition

Phosphorus is one of the major nutrient elements for plant growth. Soil phosphorus-deficiency seriously limits the high and stable yield of rice, therefore, reasonable use of phosphorus fertilizer is one of the key agronomic measures to keep continuous high yield of rice. From 1980 to 2010, phosphorus application rate increased twice, with only 90% increase in rice yield, indicating phosphorus fertilizer application failed to give full play of yield-increasing effect. It is estimated that the minable phosphate rock will be depleted in 60-100 y. Organic fertilizer could decrease phosphorus adsorption rate and increase soil phosphorus availability. Therefore, reasonable application of organic fertilizer with chemical phosphorus fertilizer is of great significance for improving crop productivity, reducing the cost of production and the phosphate rock resource depletion. Previous studies showed that combined application of organic fertilizer with chemical phosphorus fertilizer have great effects on soil phosphorus transformation and crop uptake, however, in the system of double cropping rice, effects of combined application of organic manure with phosphorus fertilizer on paddy soil phosphorus transformation and phosphorus absorption and utilization by rice plants haven’t been studied. Pot experiment, soil column experiment, and soil phosphorus release experiment under simulated condition were performed on three types of soil (paddy soil, moisture soil, and black soil) using soil enzymatic method, phosphorus fraction and release kinetics. This paper aimed at studying the effects of combined application of organic manure with phosphorus fertilizer on soil water extractable phosphorus, phosphatase activity, and phosphorus absorption and utilization by rice, to study the migration features of soil phosphorus under different treatments, the effects of soil phosphorus release and transformation under repeated combined application. The main results were as follows:1. Pot experiment was shown that compared with farmer practice (FP), combined treatments CM(P), CM(P)F, CM(-P), CM(-P)F could increase water extractable phosphorus and the phosphatase activity in panicle primordium differentiation stage. Water extractable phosphorus under continuous flooding control was significantly higher than that under drying and wetting. Correlation analysis showed that, at the tillering period and full heading stage, water soluble inorganic phosphorus, water soluble inorganic phosphorus and phosphatase activity had highly significant (P<0.01) positive correlation between each other at the tillering period. Under continuous flooding control, combined application could significantly increase the grain biomass, grain yield. Combined application could significantly increase the phosphorus use efficiency, which is higher under continuous flooding control. It can be seen that combined application of organic manure with phosphorus fertilizer could increase the extractable phosphorus, phosphatase activity and phosphorus use efficiency of early rice, insured the supply of available of nutrients during early rice growth.2. Pot experiment was shown that compared with farmer practice(FP), combined application treatments could increase water extractable phosphorus and the phosphatase activity in panicle primordium differentiation stage. Correlation analysis showed that, at the tillering period and full heading stage, water soluble phosphorus and phosphatase activity had highly significant (P<0.01) positive correlation between each other. Treatments under continuous flooding control CM(P)F significantly increase the grain biomass, phosphorus accumulation, and phosphorus use efficiency. Combined application could significantly increase the phosphorus use efficiency, which is higher under continuous flooding control. Therefore, combined application of organic manure with phosphorus fertilizer could increase the extractable phosphatase activity, which could promote organophosphate hydrolysis, insured the water extractable phosphorus availability and the accumulation of phosphorus during late rice growth.3. Soil column experiment was shown that compared with farmer practice(FP), combined application treatments CM(P1), CM(P2), CM(P3), CM(-P) increased the accumulation of water soluble phosphorus. The accumulation of water soluble phosphorus was increasing by organic fertilizer proportion. Compared with farmer practice(FP), combined application treatments increased the net accumulation of water soluble phosphorus. The amount of water soluble phosphorus in the leachate was most in moisture soil, followed by paddy soil, black soil was the least.4. The experiment of soil phosphorus release and fraction was shown that, compared with farmer practice (FP), combined application treatments CM(P), CM(-P) could increase the release of water soluble phosphorus. Combined application CM(P) increased Pi and Po in labile forms and stable forms, while CM(-P) only increased NaHCO3-Po and NaOH-Po. Therefore, combined application of organic manure with phosphorus fertilizer could increase the pool of P; and Po. CM(-P) ensure the Pi pool and increase the Po pool compared with farmer practice (FP).