【作者】 赵琳琳；

【导师】 朱强；

【作者基本信息】 华中农业大学 ， 植物营养学， 2022， 硕士

【摘要】 冬闲田种植紫云英和稻草还田是南方稻田培肥增效的重要措施。本研究基于紫云英-水稻轮作模式,采用¹⁵N自然丰度法对豆科绿肥-紫云英的生物固氮量及其向水稻的转移量进行测定,同时根据水稻的养分吸收规律、紫云英和稻草还田后的腐解及养分释放规律、土壤和田面水中氮素的动态变化,探究翻压紫云英对稻田氮素的调控作用及其与稻草联合还田的优势效应,以期为稻区制定科学的减肥增效策略提供数据支撑。主要结果如下:（1）以不施氮肥且稻草不还田条件下的黑麦草-水稻轮作模式为参比,采用¹⁵N自然丰度法测得紫云英的生物固氮率为60.5%～71.0%,生物固氮量为42.7～76.0 kg/ha;紫云英翻压还田后其生物固定的氮素累计向水稻转移了7.2～30.3 kg/ha,水稻直接利用其生物固氮量的17.3%～39.8%。（2）与单施100%常量氮肥处理（N100）相比,减氮40%的条件下,紫云英单独还田（MN60）及其与稻草联合还田处理（SMN60）的水稻产量均有增加的趋势,2019～2021三年中两处理产量的增幅分别为2.1%～11.7%、4.3%～9.4%;在100%氮水平下,紫云英单独还田（MN100）及其与稻草联合还田处理（SMN100）三年增幅分别为3.2%～5.6%、10.6%～18.7%。两者联合还田使水稻增产的效果优于紫云英单独还田,且在联合还田的条件下,减氮40%与100%氮肥水平的产量无显著差异。（3）与N100处理相比,MN60处理和SMN60处理均能保障各生育期水稻对养分的吸收利用,整体上SMN60处理的水稻养分含量和累积量高于MN60处理。在相同的还田措施下,与减氮40%相比,100%氮水平提高了各生育期的养分累积量,但并未显著提高水稻产量,导致养分的“奢侈吸收”。（4）翻压后的腐解过程中,紫云英所含N养分在埋袋后的10天内迅速释放,有63%在此期间被释放出来。P、K养分在埋袋后的4天内快速释放,释放率分别为67.1%、83.3%,总养分释放率为K>P>N。稻草覆盖还田后,所含的N养分在紫云英季释放约11.9%,在随后的水稻季释放较少;P、K养分在水稻季仍有释放。（5）紫云英单独还田及其与稻草联合还田提高了各个时期土壤全氮（TN）、铵态氮（NH₄⁺-N）、硝态氮（NO₃^--N）、微生物量氮（MBN）和有机质（SOM）的含量,其中以两者联合还田的提升效果最好。减氮40%并没有显著降低上述各养分的含量,仍能保障较高的土壤供氮能力。（6）与N100处理相比,MN100处理和SMN100处理增加了田面水中可溶性氮的含量,减氮40%使其含量降低,能有效降低氮素的流失风险。在2021年施基肥后的第15天,与N100处理相比,MN60处理田面水中可溶性总氮（DTN）、铵态氮（NH₄⁺-N）、可溶性有机氮（DON）含量分别降低了54.2%、85.1%、57.6%,SMN60处理使其降低了51.4%、84.7%、58.1%,差异均达显著水平。综合本试验结果来看,紫云英单独还田及其与稻草联合还田均能够替代40%的氮肥,其中两者联合还田能使土壤保持较高的供氮水平,更好地满足水稻对氮素的需求,最终达到使水稻稳产、增产的目的。更多还原

【Abstract】 The cultivation of Chinese milk vetch（M）in winter fallow season and the return of rice straw to paddy field are important practices to increase soil fertility in southern China.In the present study,the ¹⁵N natural abundance method was used to estimate the biological nitrogen fixation of leguminous green manure-M and its transfer to rice based on the M-rice rotation system.Meanwhile,we investigated the nitrogen regulation effect in paddy field through incorporating M and the advantageous effect of co-incorporating M and rice straw based on the nutrient uptake of rice,the decomposition and nutrient releasing pattern,and the dynamic changes of nitrogen in soil and surface water.The objective of this study was to provide data proof for the scientific strategy of fertilizer reduction in paddy areas.The main results are as follows:（1）Taking the ryegrass-rice rotation system without either rice straw returning or nitrogen fertilizer application as the reference,the biological nitrogen fixation rate of M was 60.5%～71.0%measured by the ¹⁵N natural abundance method.The total amount of nitrogen fixed was 42.7～76.0 kg/ha.It was measured that 7.2～30.3 kg/ha fixed N was transferred to the rice and the use efficiency of fixed N was 17.3%～39.8%.（2）Compared with the single application of 100%conventional N rate treatment（N100）,the rice yield increased for both treatments of M return alone（MN60）and combined with rice straw（SMN60）with 60%N rate.From 2019 to 2021,the yield increases of the above two treatments were 2.1%～11.7%and 4.3%～9.4%,respectively.With 100%N rate,the yield of the treatments MN100 and SMN100 increased by3.2%～5.6%and 10.6%～18.7%,respectively.Compared with M return alone,the co-incorporation of M and rice straw resulted in the higher improvement effect and there were no significant differences between SMN60 and SMN100.（3）Compared with the N100 treatment,the MN60 and SMN60 treatments were able to meet the nutrient requirement of rice at all growth stages.In general,SMN60 treatment resulted in the higher nutrient concentration and accumulation in rice than that of the MN60 treatment.Under the same residue return practice,the treatments with 100%N rate increased the nutrient accumulation at all stages but did not significantly increase rice yield compared with the 60%N treatments,thus resulted in nutrients"luxury uptake"by rice.（4）During the process of decomposition,N nutrients contained in M were released rapidly within 10 days after burying the bags and 63%of them were released during this period.P and K nutrients were released rapidly within 4 days,with the release rates of67.1%and 83.3%,respectively.The total nutrient release rate was K>P>N.After returning,11.9%of N was released from rice straw in the M season and very little N was released subsequently,while P and K could be released in the following rice season.（5）The contents of soil total N,inorganic N,microbial biomass N and organic matter were improved by returning M alone and combined with rice straw,among which the combined returning resulted in the highest effect.Nitrogen reduction by 40%did not significantly reduce the content of the above nutrients and still maintained a high soil nitrogen supply capacity.（6）Compared with the N100 treatment,the content of dissolved N in surface water increased in MN100 and SMN100 treatments while decreased for the treatments of MN60and SMN60,which could effectively reduce the risk of N loss.At day 15 after basal fertilizer application in 2021,the content of dissolved total N,ammonium N,and dissolved organic N in the surface water was significantly reduced by 54.2%,85.1%,and57.6%,respectively,in MN60 and by 51.4%,84.7%,and 58.1%,respectively,in SMN60treatment.The results of this study showed that both M alone and combined with rice straw could replace 40%of the nitrogen fertilizer,and the combined return of the two crop residues could maintain a higher level of soil nitrogen supply capacity,better meet the nitrogen demand of rice,and finally achieve the purpose of stabilizing and increasing the rice yield.更多还原