基于定位试验和EPIC模型的油稻两熟田磷素整体利用效率研究

Phosphorus using efficiency is one of the continuous hotspots in agricultral science，however few researches (Longterm and Quantitative Research) has been carried out for the whole usiing efficiency of phosphorus in oilseed rape-rice field. .By integrating world wide results and private practical basis, a new integrating approach with both field experiments and computer modeling (EPIC model) will be used in this research. Objectives of this research are 1)To clarify the impacts of longterm phosphorus input and straw mulching on phosphorus transporting and its using efficiency. 2) To point out some advices for farmers to use phosphorus wholely and effectively in oilseed rape-rice field..Experiment in this research will include two parts, field experiment and computer simulation (by EPIC model). 1) Phosphorus,forms and content,in soil will be compared among different treatments, then the effect of longterm phosphorus input and straw mulching on phosphorus changes and effectiveness will be analyzed on the basis of this comparison. More stress will be put into the research of phosphorus distribution and its efectiveness. 2) Phosphorus content of different tissues will be compared among diffenent treatments. Then the whole using efficiency of phosphorus will be researched based on this analizing results and phosphorus content in soil. More attention will be taken into the aftereffect of phosphorus in oilseed rape-rice field. 3) The impacts of longterm (30 years) phosphorus input and straw mulching on phosphorus transporting and its using effeciency will be researched based on simulation results of the EPIC model. At last, some phosphorus regulating methods for oilseed rape-rice rotation system will be point out in the hilly region of Northeast Sichuan Province.

磷的高效利用问题一直是国内外农业研究的热点，然而，关于油稻两熟田磷肥整体利用效率的长期定量研究还鲜见报道。本研究拟采用长期定位试验与EPIC模型模拟相结合的方法，定量研究长期（30年）磷肥投入和秸秆覆盖对油稻两熟田磷素运移规律的影响，明确磷肥的后效效应，探索提高磷肥整体利用效率的途径与方法。1）比较不同处理土壤中各形态磷素含量及剖面分布的动态差异，研究长期磷肥投入和秸秆覆盖对油稻两熟田磷素存在形态及其动态变化规律的影响，重点明确长期施磷和秸秆覆盖对磷素有效性及土层分布的影响。2）比较不同处理下作物组织中磷素含量，结合土壤磷素含量等指标，研究长期磷肥投入和秸秆覆盖对油稻两熟田磷肥整体利用效率的影响，重点明确磷肥的后效效应。3）基于EPIC模型，优化传统磷肥调控措施，探索适宜川东北丘陵区油稻两熟田的磷肥整体调控措施，为实现磷素的高效可持续利用提供必要理论依据和实践基础。

磷的高效利用问题一直是国内外农业研究的热点，然而，关于油稻两熟田磷肥整体利用效率的长期定量研究还鲜见报道。本研究采用长期定位试验与EPIC模型模拟相结合的方法，定量研究长期磷肥投入和秸秆还田对油稻两熟田磷素运移规律的影响，明确磷肥的后效效应，探索提高磷肥整体利用效率的途径与方法。研究结果表明，1）适当的油菜秸秆还田和磷肥投入均有利于水稻分蘖和产量增加。与油菜秸秆不还田相比，油菜秸秆还田处理的水稻最高分蘖增加2.5%-11.4%，增产6.7%-28.2%；与不施磷肥相比，水稻最高分蘖增加2.2%-32.8%，增产4.1%-40.3%。但过量油菜秸秆还田导致土壤环境恶化，不利于水稻返青，进而影响水稻产量提高；过量磷肥投入虽然增加了最高分蘖数但其分蘖成穗率显著降低，进而导致稻田磷肥利用效率降低。秸秆全量还田条件下，稻田P2O5投入总量以45-90kg/hm2为宜。2)EPIC模型对油稻两熟田全磷含量、有效磷含量、水稻产量和油菜产量等模拟较准确，能够满足模拟油稻两熟田磷肥运移规律和优化磷肥运筹措施的需求。模型校验结果表明，2012～2016年，土壤全磷观测值和模拟值间的R值为0.82-0.89，RRMSE值为3.2%-4.9%；土壤有效磷观测值和模拟值间的R值为0.73-0.78，RRMSE值为6.2%-8.1%。水稻产量观测值和模拟值间的R值为0.83-0.91，RMSE值为0.028-0.042 t/hm2；油菜产量模拟值和观测值间R值为0.78-0.85，RMSE值为0.008-0.027 t/hm2。3)油菜秸秆还田有利于表层土壤有效磷增加,与秸秆不还田处理相比，0-20cm土层有机磷含量增加5.3%-12.1%，有效磷含量增加2.3%-4.7%；20-40cm土层有机磷含量增加2.6%-9.7%，有效磷含量增加1.8%-2.7%；40-50cm土层土壤全磷含量显著增加，有效磷含量增加不显著。油菜秸秆还田条件下，随着磷肥施用量的增加稻田的农学利用率、磷肥偏生产力和磷肥增产效率显著降低, 当施磷量高于45kg/hm2时，磷肥处理的磷肥偏生产力减少45.1%-72.2%。秸秆全量还田条件下，油稻两熟轮作系统磷肥(P2O5)投入总量以100-120 kg/hm2为宜，其中水稻和油菜季节比例以1:3-2:3为宜。秸秆还田前期磷肥投入总量适当增加，后期适当减少。