The Effect Of Rice Straw Returning On Soil Phosphorus And Yield In Cold Areas

Straw returning was a way of sustainable development of Agriculture nowadays, the current studies suggest that it can improve soil structure, increase soil organic matter, reduced the effects of degradation and pollution caused by excessive application of chemical fertilizers. Rice Straw was the second major crop straw in China, accounting for more than 1/5 of the total output of crop straw. Phosphorus is one of the most important three elements for crop, a large number of inorganic fertilizers are applied to farmland in every year, but 80% of phosphorus was fixed. In China, the utilization rate of phosphate fertilizer is only 10% ~ 20% in the current season. Straw was very rich in phosphorus, phosphorus can be released into soil through decomposition, and so it can replace a certain amount of phosphate fertilizer. Therefore carry out studies on the effect of straw returning on phosphate in soil, it had a great practical significance. Plot experiment, laboratory simulation experiment and pot experiment were used in the test, to rice in cold area as the research object to explore effect of straw returning on soil solution soil phosphorus nutrition and yield of rice,The theoretical basis is provided for the production of rice in cold region under the condition of straw returning to field. The results showed that:Pot experiment, in the every phosphorus level, effect of straw returning in the first year of the available phosphorus and total phosphorus in soil solution are as follows: The content of available phosphorus and total phosphorus increased at tillage stage and panicle differentiation period, increased with rice straw returning amount increased. The laboratory simulation test results also show that, straw returning had a lower content of available phosphorus and total phosphorus in soil solution at early stages, but at the end of the experiment, the content of straw returning treatment and no straw returning treatment is very close. After the continuous straw returning, available phosphorus in soil solution were reduced in the whole growth period, and low straw returning decreased the most.Straw returning in the first year, available phosphorus content reduced in tillering stage of rice and increased in panicle differentiation stage and harvest stage in soil, the rule is consistent in the every phosphorus level.After long years of straw returning,in the whole rice growing period, compared with no straw returning, the content of soil available phosphorus decreased, but there is no significant difference between the high straw returning and no stra w returning treatment.In each experiment, the content of organic phosphorus in soil was decreased, but the effect of returning amount is not obvious.long years of straw returning on soil total phosphorus have an increasing effect. This effect is increased with the amount of straw returning increased, and reached significant level. Laboratory simulation experiment also proved that the effect of straw returning on soil total phosphorus content was positive.With phosphate fertilizers applied, content of available phosphorus and total phosphorus in soil solution increased with phosphorus application increasing, and most peak s of that showed in P1.5, individual treatment showed in P2 and P1. The phenomenon that available phosphorus increased by phosphorus application increasing was obviously in tiller stage and harvest stage, and not obviously in panicle initiation stage. The content of organic phosphorus also increased with phosphorus application increasing, but the difference was not significant among fertilizi ng amounts. The content of organic phosphorus had a little influence on phosphorus changing.The experiment of straw returning with phosphorus applying showed that, volume returning(P1.5) showed a higher level compared with other combinations among stages on available phosphorus in soil solution and total phosphorus, and the stage of tillering with no returning(P1.5) showed the best, the stage of panicle initiation stage and harvest stage with higher level returning(P2) showed best on available phosphorus in soil, and there was no significant difference among combinations on soil organic phosphorus, and the difference showed no significantly on total phosphorus.The adsorption isotherms of phosphorus in soil showed that, when equilibrium solution had a lower phosphorus concentration, the slope of adsorption curve was large, and the adsorption flattened with the phosphorus concentration increasing, and the returning treatment showed a higher phosphorus adsorption capacity in the same phosphorus concentration e quilibrium solution. Straw returning treatment increased the maximum amount of soil phosphorus absorption, the maximum amount of phosphate buffer and the standard phosphorus requirement, and that increased with field capacity increasing. The effect of retu rning on adsorption constant showed no discipline, the performance of panicle initiation stage in laboratory simulation experiment, pot experiment and plot experiment increased, and the performance of tillering stage and harvest stage in plot experiment reduced. Generally, Straw returning increased the adsorption capacity of the soil phosphorus, expanded soil phosphorus library, this phenomenon was more obvious after successive years of straw returning.From view of the whole plant, straw returning reduced the phosphorus absorption capacity. In the tillering stage, whether phosphorus and phosphorus accumulation were low with returning treatment. In the panicle initiation stage, rice phosphorus content had little difference between the high-phosphorus fertilizer amount and no straw returning treatment, but accumulation of phosphorus was lower. In the harvest stage, the content and accumulation of phosphorus in grain of no returning treatment was higher, but the difference was not obvious in returning treatment.In addition, from the view of straw returning and application of phosphate fertilizer,Straw returning with high phosphorus fertilizer will caused a decline in rice absorption capacity, and from the view of Phosphorus distribution, straw returning and application of phosphorus fertilizer promoted the underground phosphorus accumulation.After of continuous straw returning, the plant height had a distinct growth, and the difference was significant, other traits were not significant, rice yield increased and the difference was not significant. The yield of straw beginning returning was less than that of no returning treatment in plot experiment. The yield of the treatment of straw returning with medium phosphate fertilizer(P1.5)was better than others, and the yield of excessive phosphate fertilizer was reduced.