Effects Of Combined Application Of Organic Manure With Phosphorus Fertilizer On Soil Phosphorus Transformation And P Absorption By Rice Plant

Rice (Oryza Stiva L.) is one of important food crops in China. Phosphorus deficiency could directly affect the energy metabolism of rice plant which inhibits the growth and yield production of rice. Phosphate fertilizer (P2O5) applied in China increased from 2.7 million tons in 1980 to 13.3 million tons in 2014, and P fertilizer use efficiency was lower. It is estimated that the total nutrients amount in organic manure of livestock and others in China are about 70 million tons in 2015, however, the utilization rate of nutrients in organic manure is only 40%. It has been reported that organic manuring is helpful in increasing the rice grain yield and improving the rice quality, however, the investigation on the effects of combined application of organic manure with phosphorus fertilizer on phosphorus fertilizer efficient utilization is inadequate.In this study, a field experiment with six treatments such as 1. unfertilized CK; 2. nitrogen and potassium treatment NK; 3. the farmer familiar fertilization [FP(P)]; 4. single manure [M(20%P)]; 5. organic manure(20%)+chemical fertilizer(80%)-equal input of phosphorus fertilization treatment [CM(P)] and 6. organic manure(20%)+ chemical fertilizer(64%)-reduced input of phosphorus fertilization treatment [CM(-P)] was conducted under rice-rice cropping. The effects of different fertilization modes on soil available phosphorus and soil phosphatase activities, soil organic and inorganic phosphorus and soil phosphorus adsorption-desorption characteristics and the growth and phosphorus use efficiency of double crop rice were investigated by adopting the soil enzyme, soil phosphorus fractonation and isothermal adsorption method. The main results are as follows:1. For early rice, the rice-rice rotation field experiment showed that treatment CM(P) significantly increased soil water-soluble phosphorus concentration at the young panicle differentiation stage and Bray-P concentration at tillering stage, full heading stage and mature stage as well as the activities of soil acid phosphomonoesterase (ACP) and phosphodiesterase (PDE) at young panicle differentiation stage, the activities of soil alkaline phosphomonoesterase (ALP) at tillering stage. Treatment CM(-P) significantly increased soil water-soluble phosphorus concentrations at all four stages. For late rice, treatment CM(P) significantly increased soil water-soluble inorganic phosphorus, total water-soluble phosphorus and Bray-P concentrations at tillering stage and young panicle differentiation stage. Treatment CM(-P) significantly increased soil water-soluble inorganic phosphorus, and total water-soluble phosphorus concentrations at tillering stage and young panicle differentiation stage, as well as the activities of soil acid phosphomonoesterase (ACP) of CM(P) at young panicle differentiation stage. Soil water-soluble phosphorus and Bray-P concentrations were significantly positively correlated to the activities of ACP, ALP and PDE at young panicle differentiation stage of early or late rice. The combined application of organic manure with phosphorus fertilizer is effective for increasing water-soluble phosphorus, Bray-P concentrations, and promoting soil phosphatase activities, and ensuring adequate supply of available phosphorus for rice growth.2. Soil samples were collected at the mature stage of early and late rice. The soil phosphorus fractionation was conducted. The results showed that concentrations of all soil inorganic phosphorus forms, total extractable inorganic phosphorus and low stable organic phosphorus of FP(P), CM(P) and CM(-P) treatments significantly increased. Phosphorus fertilization or the combined application of organic manure with phosphorus fertilizer are effective for increasing soil available inorganic and organic phosphorus, and the later with a proper reduction of chemical P fertilizer input could maintain the available phosphorus level.3. Soil samples were collected at the mature stage of late rice. The soil phosphorus adsorption-desorption experiment was conducted. The results showed that the P adsorption capacity, affinity coefficient, maximum buffering capacity of FP(P), CM(P) and CM(-P) treatments were significantly reduced, and the P sorption energy (1/n) of FP(P), CM(P) and CM(-P) treatments were significantly increased with the comparison to CK, NK and M(20%P) treatments, and the soil P desorption amount and ratio of FP(P), CM(P) and CM(-P) treatments were significantly higher than those of CK, NK and M(20%P) treatments under the same level of P adsorption saturation. Phosphorus fertilization or the combined application of organic manure with phosphorus fertilizer could reduce the P adsorption capacity, increase P desorption, release more labile phosphorus, and improve soil P supply capacity.4. It was found that nitrogen, phosphorus, potassium amounts accumulated in shoots of early rice, and shoot biomass of FP(P), CM(P) and CM(-P) treatments were significantly higher than those of CK, NK and M(20%P) treatments at young panicle differentiation stage. The grain yield, shoot biomass and phosphorus accumulation of FP(P), CM(P) and CM(-P) treatments were significantly higher than those of CK and M(20%P) treatment at mature stage of early rice. There was no significant difference among the phosphorus recovery use efficiency and phosphorus agronomic use efficiency among FP(P), CM(P) and CM(-P) treatments. The partial factor productivity for applied P of CM(P) and CM(-P) treatments were significantly higher. Phosphorus fertilization or the combined application of organic manure with phosphorus fertilizer could meet the phosphorus need of early rice and promote growth and tillering at the early growth period, as well as stabilize grain yield, nutrient accumulation, phosphorus agronomic use efficiency and phosphorus recovery use efficiency, and the later with a proper reduction of chemical P fertilizer input could increase the partial factor productivity of applied P.5. It was found that nutrient amounts accumulated in shoots of late rice, and shoot biomass of FP(P), CM(P) and CM(-P) treatments were significantly higher than those of CK and M(20%P) treatments at young panicle differentiation stage. The grain yield, shoot biomass and phosphorus accumulation of FP(P), CM(P) and CM(-P) treatments were significantly higher than those of CK, NK and M(20%P) at mature stage of late rice. Phosphorus agronomic use efficiency and partial factor productivity of CM(P) and CM(-P) treatments were significantly higher. The phosphorus recovery use efficiency of CM(-P) were significantly increased. Therefore, the combined application of organic manure with phosphorus fertilizer could meet the phosphorus need of late rice and promote growth and tillering at the early growth period, as well as stabilize grain yield, nutrient accumulation, improve the phosphorus agronomic use efficiency and phosphorus recovery use efficiency, and the later with a proper reduction of chemical P fertilizer input could increase the phosphorus agronomic use efficiency for applied P.