填闲作物紫云英对稻田氮素形态变化及其生产力的影响机理

发布时间：2018-06-07 00:39

  本文选题：填闲作物 + 紫云英　； 参考：《华中农业大学》2016年博士论文

【摘要】：氮素形态转化与循环过程是元素生物地球化学过程中的重要一环。水稻(Oryza sativa L.)是我国主要种植的三大粮食作物之一。氮素是水稻等作物生长发育以及形成一定产量的首要限制性因素。自改革开放以来,我国长期不合理施用化肥尤其是氮肥,至上世纪90年代末,无论是氮肥施用总量还是施用强度均已位居世界前列,而有机物料投入用量则骤然下降。随着时间的推移,由于长期过量且不合理施用氮肥,不仅其当季利用率比较低,大量硝态氮累积于土壤中而产生下渗淋溶损失、NH3挥发和硝化反硝化脱氮(NOx)等途径损失进入土壤、水体和大气等环境中而引发一系列环境问题,而且氮肥的增产效益逐年下降。种植和利用冬季填闲作物是我国传统农业的精华和重要组成部分,其鲜草还田经土壤微生物腐解释放出来的氮素同样可被水稻作物吸收利用,还可能影响了土壤氮库中各形态氮素分布、转化及其归趋等一系列生物地球化学过程,从而影响氮素生物有效性以及稻田生产力的可持续性。以往关于填闲作物的多研究集中于旱地土壤或者更关注于其在培肥改土、供应下茬作物养分等方面的作用,而关于填闲作物对淹水稻田系统土壤供氮能力和水稻生产力持续变化以及氮素形态转化的作用等方面的机制尚不清楚。因此,本文拟采用紫云英(Astragalus sinicus L.)为模式填闲作物,通过大田长期定位试验、室内盆栽和15N示踪(交叉标记)微区试验相结合的方法,探讨填闲作物对氮素形态转化、硝化反硝化等过程以及稻田供氮能力及其生产力持续演化过程的影响机理,研究结果将对外源物质投入相对较少的南方水稻种植体系中合理利用填闲作物,提高稻田土壤中氮素贮藏和循环能力和利用率,减少稻田氮素损失及其环境风险,维持稻田系统生产力与可持续性具有十分重要的意义。主要结论如下:1.采用室内土壤盆栽试验研究了尿素配施紫云英对单季稻田系统氮素气态损失的影响。结果表明,单季稻田氮素的NH3挥发损失率超过20%,而N2O损失率则小于1%。与尿素单施相比,尿素配施紫云英显著降低表面水中铵态氮含量和分蘖期土壤中羟胺还原酶活性以及各生育期土壤中硝化反硝化细菌数量与硝酸和亚硝酸还原酶活性,从而分别显著降低单季稻田NH3挥发量和N2O排放量14.6%和45.2%,进而分别降低N2O的增温潜势和温室气体强度45.2%和46.8%。2.与尿素单施相比,尿素配施紫云英显著增加水稻各生育期土壤中固定态铵、土壤微生物量碳与氮含量以及铵态氮和非酸解氮(NAHN)含量,却降低硝态氮含量;增加氨基酸态氮(AAN)、氨基糖态氮(ASN)和酸解氨态氮(AHAN)含量,而降低酸解未知态氮(AHUN)含量,从而分别增加无机氮、酸解氮(AHN)和总氮含量5.13%-24.2%、3.44%-8.36%和9.17%-10.9%,新增加的AHN中以AAN和AHAN为主。3.与尿素单施相比,尿素配施紫云英分别显著增加土壤中细菌、放线菌、真菌、固氮菌数量和脲酶、蛋白酶、蔗糖酶活性14.5%-36.6%和15.3%-31.1%,但分别显著降低土壤中氨氧化细菌(AOB)数量和氨氧化古菌基因(AOA amo A)丰度24.6%和66.4%;显著降低15NU对分蘖期土壤中ASN、AHUN、AHAN和NAHN及其对成熟期土壤中AAN和ASN的贡献率,却显著增加其对成熟期土壤中AHUN、NAHN和固定态铵的贡献率。通径分析结果则表明,AHAN是土壤中15NU的暂时累积库,而NAHN则是稳定的储存库。4.与尿素单施相比,尿素配施紫云英促进水稻各生育期对15NU的吸收累积及其在实籽粒中的分配量,降低其对土壤氮(SoilN)的吸收累积以及15NU在秕谷中的分配量,从而显著提高15NU利用率46.1%-83.0%,降低水稻对土壤氮素的依存率14.0%,改善产量各构成要素(每穗实粒数、结实率和千粒重),从而增加籽粒产量3.02%。5.水稻收获后,种植填闲作物紫云英分别显著增加盛花期土壤总氮、固定态铵、土壤微生物量氮和铵态氮含量,降低硝态氮含量;增加盛花期土壤中AAN、ASN和AHAN含量,降低AHUN含量,最终分别平均增加酸解氮和非酸解氮含量13.0%和15.9%,另外,种植填闲作物紫云英还显著增加残留15NU对盛花期土壤中铵态氮、AAN、ASN和AHAN的贡献率6.31%-22.3%,而分别降低其对土壤总氮、硝态氮、固定态铵和AHUN、AHN、NAHN的贡献率8.28%-85.7%和6.37%-33.2%。6.在大田条件下,研究了紫云英和尿素不同配比(紫云英氮分别替代20%-80%尿素氮)对双季稻田系统土壤供氮能力及其生产力可持续演变过程的影响。结果表明,不施肥或者尿素单施均不利于稻田系统生产力的可持续性发展。N80M20或N60M40处理条件下,耕层土壤有机质和总氮含量以及早稻、晚稻籽粒和秸秆及其周年产量均随时间的推移呈增加趋势,而N100、N40M60或N20M80处理早稻、晚稻籽粒和秸秆及其周年产量变化趋势则相反。与N100相比,N80M20或N60M40处理显著提高耕层土壤有机质、总氮、铵态氮含量和无机氮总量,促进水稻地上部对氮素的吸收累积,提高水稻籽粒和秸秆周年产量及其可持续指数以及氮素农学利用率和偏生产力,而N40M60或N20M80处理则均表现为显著降低趋势。另外,紫云英替代尿素均显著降低耕层土壤硝态氮含量。
[Abstract]:Nitrogen form transformation and circulation process is an important part of the elemental biogeochemical process. Rice (Oryza sativa L.) is one of the three major grain crops planted in China. Nitrogen is the primary limiting factor for the growth and development of rice and other crops. Since the reform and opening up, China has been using fertilizer for a long time. In particular, nitrogen fertilizer, at the end of the 90s of the last century, both the total amount of nitrogen fertilizer application and the application intensity have been in the forefront of the world, while the amount of organic materials dropped suddenly. With the passage of time, due to the long and unreasonable application of nitrogen fertilizer, not only the utilization ratio of the nitrogen fertilizer is lower, but a large amount of nitrate nitrogen is accumulated in the soil. Loss of leach, NH3 volatilization and nitrification denitrification and denitrification (NOx) are lost into the soil, water and atmosphere, which cause a series of environmental problems, and the benefits of nitrogen fertilizer increase year by year. Planting and utilization of winter leisure crops is the essence and important part of traditional agriculture in China, and its fresh grass is returned to soil by soil microorganism. The nitrogen released by decomposition can also be absorbed and utilized by rice crops, and it may also affect the distribution of nitrogen in the soil nitrogen pool, transformation and its return to a series of biogeochemical processes, thus affecting the bioavailability of nitrogen and the sustainability of the productivity of rice fields. Soil may be more concerned with the role of soil nutrient in the soil and the supply of crop nutrients, while the mechanism for soil nitrogen supply capacity and the continuous change of rice productivity and the role of nitrogen morphologic transformation in the flooded rice field system are not clear. Therefore, this paper is to use Astragalus sinicus L. as a model. In this paper, the mechanism of nitrogen morphologic transformation, nitrification and denitrification, nitrogen supply capacity and the continuous evolution of productivity in paddy fields were discussed by long-term location test in field and combined with 15N tracer microarea test. The results of the research will be relative to foreign substances. It is of great significance to improve nitrogen storage and recycling capacity and utilization in paddy soil, reduce nitrogen loss and environmental risk in paddy soil, reduce nitrogen loss and environmental risk in paddy soil, and maintain the productivity and sustainability of rice field system. The main conclusions are as follows: 1. a pot experiment in indoor soil was used to study urea. The results showed that the loss rate of NH3 volatilization of nitrogen in single season rice field was more than 20%, while the loss rate of N2O was less than that of 1%. compared with that of urea in single application. Urea was significantly reduced in the surface water and the activity of hydroxylamine reductase in the tillering stage and the soil of each growth period. The number of nitrification and denitrifying bacteria in the soil and the activity of nitric acid and nitrous reductase significantly decreased NH3 volatilization and N2O emissions by 14.6% and 45.2% in single cropping rice fields, respectively, and then decreased the temperature potential of N2O and the greenhouse gas intensity 45.2% and 46.8%.2., respectively, compared with the single application of urea. The medium fixed ammonium, soil microbial biomass carbon and nitrogen content, ammonium nitrogen and non acid nitrogen (NAHN) content decreased nitrate nitrogen content, increased amino acid nitrogen (AAN), amino sugar nitrogen (ASN) and acid ammonia nitrogen (AHAN) content, and decreased the content of unknown nitrogen (AHUN) in acid solution, thus increasing the content of inorganic nitrogen (AHN) and total nitrogen content 5.13%-2 respectively. 4.2%, 3.44%-8.36% and 9.17%-10.9%, compared with the single application of AAN and AHAN in the newly added AHN, the application of urea to the application of the urea with the urea and the application of the urea to the actinomycetes, fungi, nitrogen fixing bacteria and urease, protease, invertase activity 14.5%-36.6% and 15.3%-31.1% respectively, respectively, decreased the amount of ammonia oxidizing bacteria (AOB) in the soil, respectively. The abundance of AOA amo A was 24.6% and 66.4%, and the contribution rate of 15NU to ASN, AHUN, AHAN and NAHN and their contribution to AAN and ASN in the mature soil were significantly reduced, but the contribution rate to AHUN, NAHN and fixed ammonium in mature soil was significantly increased. In addition, NAHN is a stable storage.4.. Compared with single application of urea, urea is used to promote the absorption and accumulation of 15NU in each growth period of rice and its distribution in the real grain, the absorption and accumulation of nitrogen (SoilN) and the distribution of 15NU in the grain, thus significantly improving the 15NU utilization rate 46.1%-83.0% and reducing rice. The dependence rate of soil nitrogen was 14%, improving the yield components (the number of grain per panicle, seed setting rate and 1000 grain weight), thus increasing grain yield 3.02%.5. rice after the harvest, the planting and filling crops increased significantly the total soil nitrogen, fixed ammonium, soil microbiological nitrogen and ammonium nitrogen content, and decreased nitrate nitrogen content; The content of AAN, ASN and AHAN in the flowering soil decreased AHUN content, and the content of acid nitrogen and non acid nitrogen was increased by 13% and 15.9%, respectively. In addition, the contribution of residual 15NU to ammonium nitrogen, AAN, ASN and AHAN in the flowering soil was 6.31%-22.3%, and the total nitrogen, nitrate nitrogen and immobilization were reduced respectively. The contribution rate of ammonium and AHUN, AHN, NAHN was 8.28%-85.7% and 6.37%-33.2%.6. in field conditions, and the effects of different proportions of carbamide and urea on the capacity of soil nitrogen supply and the sustainable evolution of productivity in the system of double cropping rice field were studied. The results showed that no fertilization or single application of urea was not favorable. Under the condition of the sustainable development of rice field system productivity, the content of organic matter and total nitrogen in the soil and the yield of early rice, late rice grain and straw and their annual yield increased with time under.N80M20 or N60M40 treatment conditions, while N100, N40M60 or N20M80 treatment of early rice, late rice seed and straw and the trend of annual yield changes were the opposite. Compared with N100, N80M20 or N60M40 treatment significantly improved soil organic matter, total nitrogen, ammonium nitrogen and total inorganic nitrogen, promoted the accumulation of nitrogen in the upper part of rice, increased the annual yield and sustainability index of rice grain and straw, as well as nitrogen agronomy utilization and partial productivity, while N40M60 or N20M80 treatment showed significant difference. In addition, the substitution of Chinese milk vetch for urea significantly reduced nitrate nitrogen content in the topsoil.
【学位授予单位】：华中农业大学
【学位级别】：博士
【学位授予年份】：2016
【分类号】：S158;S142.1
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本文编号：1988876