Effects Of NPK Fertilizer Application On Straw Decomposition,Rice Yield And Nutrient Absorption And Utilization Under Wheat Straw Incorporation Condition

Straw is an important nutritious resource,which plays a critical role in recycling nutrients when return to the field.The content of some macroelement such as phosphorus in straw is relative low that may not satisfy the demand of plant.People usually combine chemical fertilizer with straw incorporation in order to fit the nutritious requirement of crop during the growing stage.In recent studies,people often focus on the effect of straw incorporation on soil nutrient status and yield of crop,but very few studies concentrated on the rice yield and nutrient utilization efficiency under condition of straw incorporation plus different chemical fertilizer management at long term experiment.While fertilizer application after straw residue incorporation as well as the quantities of chemical fertilizer addition at different growing stages is still unknown.Our study adopts the long term field experiment to investigate the influence of fertilizer management under the condition of wheat straw incorporation on rice yield and nutrient absorption,and to analyzes the dynamic alteration of soil fertility and the nutrient utilization efficiency under the condition of continuous straw incorporation.?1?The wheat straw residues decomposition well fitted the first-order kinetic equation.The decomposition rates of the wheat straw residue under the NS?nitrogen plus straw composting?,ES?effective microorganisms plus straw composting?treatments were 74.70%and 73.26%,respectively after incubation for 120d.While it was 79.83%under the NESS?nitrogen and effective microorganisms plus straw composting?treatment.The decomposition rate constant expressed the trend of K_NESS>K_NS>K_ES>K_S,and the highest decomposition rate constant was found in the treatments of NESS.The nitrogen fertilization combined with effective microorganisms greatly stimulated the decomposition of wheat straw by increasing the activities of peroxidase,as well as accelerated the decomposition of refractory fraction in wheat straw residues at the late stage of decomposition.In summary,nitrogen fertilizer as well as the effective micro-organism can accelerate the decomposition of wheat straw residue,the former accelerated the decomposition of wheat straw by increasing the activities of hydrolase,whereas the later accelerated the decomposition of wheat straw by increasing the activities of oxidase.?2?As the wheat straw incorporation,20%of N advanced from heading stage to basal stage?basic:tillering:panicle=6:3:1?increased soil alkaline N by 20.23%,but it had no significant influence on soil organic matter and total N.Advancing of N from heading stage to basal stage?basic:tillering:panicle=6:3:1?can increased total and net nitrogen accumulative amount,and rice yield by 12.93%,10.06%,and 10.37%,respectively.While it also significantly increased rice effective panicles by 7.05%,and improved nitrogen contribution rate,agronomic efficiency of nitrogen,nitrogen partial factor productivity,and nitrogen recovery efficiency by 32.21%,135.11%,21.99%and 174.12%,respectively.?3?The content of both soil available P and inorganic P decreased with the reduction of P fertilizer application as the wheat straw incorporation,but the organic P is increased with the P fertilizer reducing application.Reduction of P by 30%increased total and net phosphorus accumulate in rice by 40.12%and 41.67%,respectively,but it decreased rice yield?P>0.05?.The reduction of P application as wheat straw incorporation increased phosphorus contribution rate,agronomic efficiency of phosphorus,phosphorus partial factor productivity,and phosphorus recovery efficiency by 11.14%,9.13%,123.63%and 8.48%,respectively.?4?Compared with wheat straw return plus formula fertilization(K_100%),wheat straw return plus formula fertilization and potassium reduction by 10%(K_90%)increased soil available and total potassium by 6.38%,3.31%,increased the total and net potassium accumulation in rice by 1.55%and 5.13%,respectively.Wheat straw return plus formula fertilization and potassium reduction more than 20%(K_80%and K_70%)decreased soil total K and available K by 12.58?15.31%and 4.26?10.64%,decreased the total potassium accumulation in rice by 7.49?13.62%?P<0.05?,respectively.Both K_80%and K_70%increased the net potassium accumulation in rice by0.48%?1.78%.K_80%increased rice yield by 2.32%,whereas K_70%decreased rice yield by 6.43%.Compared with K_100%,wheat straw return plus formula fertilization and potassium fertilization reduction(K_90%,K_80%,K_70%)significantly increased agronomic efficiency?15.51?24.53%?,partial productivity?17.96?25.40%?,potassium absorption and utilization efficiency?17.53?55.36%??P<0.05?of rice.Comparing CK without potassium fertilizer application,reduction of K fertilizer over 20%had a potential risk of decreasing the economic profit.