【作者】 黄景；

【导师】 顾明华；

【作者基本信息】 广西大学 ， 作物栽培学与耕作学， 2012， 博士

【摘要】 为了探讨免耕对稻田氮素利用、转化、迁移与平衡及土壤质量的影响,本文通过田间试验比较了普通免耕(CNT)、稻草还田免耕(SNT)、普通常耕(CCT)和稻草还田常耕(SCT)4种耕作方式对稻田土壤有效态氮转化、施肥后田面水氮素转化、施肥后稻田氨挥发、氮素淋溶、水稻生长、水稻地上部全氮、水稻氮素利用率、土壤剖面形态性质、土壤理化性质、土壤酶活性以及土壤微生物数量的影响。结果表明：1、免耕稻田土壤氮素转化免耕降低了0-5cm土层硝态氮和5-20cm土层碱解氮含量、提高了施肥后第1天至6天田面水的铵态氮、硝态氮和总氮含量。有无稻草还田对稻田氮素转化影响明显,CNT处理提高了5-20cm土层硝态氮和0-5cm土层灌浆期以前碱解氮含量；降低了0-20cm土层土壤铵态氮含量。SNT处理提高了0-5cm土层土壤铵态氮和碱解氮含量、比CNT处理降低了施肥后田面水的铵态氮、硝态氮和总氮含量。2、免耕稻田氮素迁移免耕增加了施肥后第1天至第6天氨挥发量和水稻各生长期氨挥发量、增加了氮素淋溶量。有无稻草还田对稻田氮素迁移影响明显,CNT处理减少了水稻吸氮量和土壤氮素残留量。SNT处理增加了土壤氮素残留量、比CNT处理减少了施肥后第1天至第6天氨挥发量和水稻各生长期氨挥发量以及氮素淋溶量、比CCT处理增加了水稻氮素吸收量。3、免耕稻田氮素平衡耕作方式与稻草还田对稻田氮素平衡影响明显。CNT稻田土壤氮素输入量大体上与CCT稻田相当,但输出量增加,土壤全氮增幅减少；SNT稻田土壤氮素输入量大体上与SCT稻田相当,但输出量减少,土壤全氮增幅增加；SNT比CNT显著增加土壤全氮含量。稻草还田对维持免耕稻田氮素平衡起到重要作用。4、免耕水稻生长与氮素利用稻草还田促进了水稻生长和增加了水稻氮素吸收量,提高了水稻氮素回收效率。稻田免耕后,CNT处理水稻株高、分蘖数、有效穗数、叶面积、叶片的硝酸还原酶活性、RuBP羧化酶蛋白含量、干物质累积量、叶片和茎的全氮含量、氮素累积量、氮素回收效率和产量均为处理中最低,但穗全氮含量、氮素稻谷生产效率、氮素运转效率和氮素收获指数为处理中最高。SNT处理水稻株高、分蘖数、有效穗数、叶面积、叶片的硝酸还原酶活性、RuBP羧化酶蛋白含量、干物质累积量、叶片和茎的全氮含量、氮素累积量、氮素农艺效率、氮素回收效率和产量高于CCT处理,但氮素稻谷生产效率、氮素运转效率和氮素收获指数低于CCT处理。5、免耕对土壤剖面形态的影响免耕对土壤剖面形态产生了深刻的影响,有无稻草还田免耕形成的土壤剖面形态也存在差异。免耕对Ap层(犁底层)、W层(潴育层)和C层(母质层)的形态影响不明显,但Aa(耕作层)的形态产生了较大的变化。CNT处理形成了Aa1-Aa2-Aa3的耕作层亚层构型；SNT处理形成了O-Aa1-Aa2-Aa3的耕作层亚层构型,O层是有机质覆盖层,由不同分解程度稻草组成,是SNT独特的剖面发生层。免耕处理Aal层比常耕处理的薄,但免耕处理的Aal层色调深、容重小、结构好、pH低、根系密集、孔隙多、疏松。与SNT处理相比较,CNT的Aa2和Aa3层则色调浅、容重大、根系和孔隙少、鳝血斑数量少、裂隙出现部位高、紧实。SNT的Aa2和Aa3层剖面形态性质和特征与常耕的相应土层相当。6、免耕对稻田土壤物理性质的影响免耕提高了0-5cm土层持水性能,增加了>1mm水稳性大团聚体数量。SNT处理5-20cm土层持水性、有效水含量范围、水稳性大团聚体数量与常耕土壤相当,但CNT处理5-20cm土层持水性能降低、有效水含量范围和水稳性大团聚体数量减小。7、免耕对稻田土壤化学性质的影响免耕使土壤有机碳、腐殖质、氮素、磷素和钾素在表层土壤富集,提高了表层有效锌、有效硼含量,降低了表层土壤pH值、交换性钙、交换性镁和有效铜含量。免耕处理耕作层的5-20cm层土壤有机碳、腐殖质、全氮、全磷、全钾、碱解氮、速效磷、速效钾、阳离子交换量、交换性钙、交换性镁、有效锌和有效硼含量小于常耕土壤,其中CNT减少的幅度大于SNT。免耕处理Ap层、W层和C层的pH值、有机碳、全氮、全磷、全钾与常耕处理差异不明显,Ap层、W层和C层的交换性钙、交换性镁、有效铜及W层和C层的碱解氮、速效钾、有效锌和有效硼均有增加的趋势。8、免耕对稻田田田土壤酶活性的影响免耕提高了0-5cm层土壤的蔗糖酶、脲酶、蛋白酶、过氧化氢酶和多酚氧化酶等酶的活性,其中以SNT处理增幅最大,但降低了耕作层5-20cm层土壤的蔗糖酶、脲酶、蛋白酶、过氧化氢酶和多酚氧化酶等酶的活性,其中以CNT处理降幅最大。9、免耕对稻田土壤微生物数量的影响免耕增加了0-5cm层土壤真菌、放线菌数量,其中以SNT处理增幅最大,减少了耕作层亚硝化细菌和5-20cm层土壤细菌、真菌、放线菌、氨化细菌、嫌气性固氮菌、好气性纤维素分解菌、嫌气性纤维素分解菌数量,其中以CNT减幅最大。SNT处理增加了表层0-5cm土壤细菌、氨化细菌、好气性纤维素分解菌的数量,其中SNT处理0-20cm土层的氨化细菌、0-12cm土层的真菌和放线菌数量显著大于其它处理。因此,稻草还田免耕对水稻的生长、产量和氮素利用及土壤肥力性状的效应优于普通常耕。更多还原

【Abstract】 In order to evaluate the influence of no-tillage on change of soil available nitrogen, transformation of nitrogen content of paddy field after fertilization, ammonia volatilization, nitrogen leaching, rice uptake nitrogen, soil residue nitrogen, nitrogen balance, rice growth, rice nitrogen content, rice nitrogen efficiency, soil profile properties, soil physical and chemical properties, soil enzyme activities and soil microorganism quantity of paddy field, Field experiments with four treatments, common no-tillage (CNT), no-tillage with rice straw returning (SNT), common conventional tillage (CCT), conventional tillage with rice straw returning (SCT) were carried out.The main results are as follows.1. Transformation of soil nitrogen in no-tillage paddy fieldNitrogen transformation of paddy soil were obviously affected by no-tillage for the change of tillage and fertilization as compared with conventional tillage. Contents of nitrate nitrogen in0-5cm soil layer and alkaline-hydrolyzable nitrogen in5-20cm soil layers were reduced, but contents of ammonium nitrogen, nitrate nitrogen and total nitrogen of soil surface water were increased in1-6days after fertilization under no-tillage condition. Rice straw returning made an obvious influence on nitrogen transformation. Treatment of CNT increased contents of nitrate nitrogen in0-20cm soil layer, contents of alkaline-hydrolyzable nitrogen in0-5cm soil layer before filling stage, but reduced content of ammonium nitrogen in0-5cm soil layer. Treatment of SNT increased contents of nitrate nitrogen and alkaline-hydrolyzable nitrogen in0-5cm soil layer, but declined contents of ammonium nitrogen, nitrate nitrogen and total nitrogen of soil surface water after fertilization as compared with CNT.2. Migration of nitrogen in no-tillage paddy fieldGreat change took place in migration of soil nitrogen in no-tillage paddy field for soil with no ploughing and surface application as compared with conventional tillage. Treatments of no-tillage increased quantity of ammonia volatilization in1-6days after fertilization and each rice growth stage, quantity of leaching nitrogen. Rice straw returning made an obvious influence on nitrogen migration. CNT reduced nitrogen quantity of rice uptake and soil residue, while SNT increased nitrogen quantity of soil residue as compared with treatments of conventional tillage. Treatment of SNT reduced nitrogen amount of ammonia volatilization in1-6days after fertilization and each rice growing stage, amount of leaching nitrogen, amount of rice uptake nitrogen as compared with treatment of CNT.3. Balance of nitrogen in no-tillage paddy fieldNitrogen balance of paddy field was obviously affected by tillage ways and rice straw returning. Nitrogen import amount of CNT was roughly equal to treatment of CCT, but nitrogen import was more, so residual nitrogen of soil was less than CCT. Nitrogen import amount of SNT was roughly equal to treatment of SCT, but nitrogen import was less, so residual nitrogen of soil was more than SCT. The treatment of SNT increased more nitrogen than that of CNT in soil. Rice straw returning plays an important role in maintaining nitrogen balance of paddy field.4. Growth and nitrogen utilization of rice under no-tillageGrowth and nitrogen utilization of rice under no-tillage was obviously affected by tillage ways and rice straw returning. Rice straw returning promoted rice to grow and absorb more nitrogen, so nitrogen recovery efficiency (NRE) of rice was increased. The rice height, amount of rice tillers, amount of rice valid tillers, rice leaf area index, rice leaves nitrate reductase activity, content of rice leaves RuBPcase, rice dry matter accumulation, nitrogen content of rice leaves and stem, total nitrogen accumulation (TNA), NRE and yield of CNT were least, but the nitrogen content of rice spike, nitrogen grain production efficiency (NGPE), nitrogen transportation efficiency (NTE), nitrogen harvest index (NHI) were most among the treatments. The rice height, amount of rice tillers, amount of rice valid tillers, rice leaf area index, rice leaves nitrate reductase activity, content of rice leaves RuBPcase, TNA, nitrogen content of rice leaves and stem, rice nitrogen accumulation, nitrogen agronomy efficiency (NAE), NRE and yield of SNT were more than CCT. 5. Influence of no-tillage on profile morphological characteristics of paddy soilNo-tillage of paddy field made an deep influence on profile morphological characteristics of paddy soil.There were obvious difference between soil profile morphological characteristics formed with rice straw returning and that formed without rice straw returning. The morphological characteristics of Ap layer (plow sole), W layer (waterloggogenic horizon) and C layer (parent material horizon) were not obviously affected by no-tillage of paddy field, but great changes took place in that of Aa layer (arable horizon). The Aa sub-constitution formed by CNT is Aal-Aa2-Aa3, while by SNT is O-Aal-Aa2-Aa3. O layer, litter layer consisted of rice straw in differently decomposed level is unique profile horizon of SNT. Aal layer of no-tillage treatments is thinner, but blacker in color, less in soil bulk density, granular in structure, lower in pH value, more root, more pore, looser than that of conventional tillage. Aa2and Aa3layer of CNT is lighter in color, bigger in soil bulk density, less root, and pore, less iron-humus mottling, with higher position of fissure and solider than that of CCT. The Aa2and Aa3layer properties of SNT are equal to that of conventional tillage.6. Influence of no-tillage on physical properties of paddy soil No-tillage increased soil water retention properties in0-5cm layer, and added amount of> lmm water stable macro-aggregate in0-5cm layer. The soil water retention properties, available moisture, amount of water stable macro-aggregate of SNT in5-20cm layer were equal to those of conventional tillage, but CNT reduced the soil water retention properties, available moisture, quantity of water stable macro-aggregate in5-20cm layer as compared with conventional tillage.7. Influence of no-tillage on chemical properties of paddy soilContent of organic carbon, nitrogen, phosphorus, potassium in upper soil layer are higher than that in lower soil layer under no-tillage. No-tillage increased content of humus, cation exchange capacity, available zinc, available boron in0-5cm soil layer, and reduced content of exchangeable calcium, exchangeable magnesium and available copper in0-5cm soil layer, lowered pH value in upper soil layer. As compared with conventional tillage, content of organic carbon, humus, total nitrogen, total phosphorus, total potassium, alkaline-hydrolyzable nitrogen, rapidly available phosphorus, rapidly available potassium, cation exchange capacity, exchangeable calcium, exchangeable magnesium, available zinc, available boron in5-20cm soil layer of no-tillage were lowerer than that of conventional tillage, and between SNT and CNT, the least reduced range was CNT. Content of alkaline-hydrolyzable nitrogen, rapidly available potassium, exchangeable calcium, exchangeable magnesium and available copper in Ap layer, W layer and C layer, content of available zinc, available boron in W layer and C layer of no-tillage tended to become higher than that of conventional tillage.8. Influence of no-tillage on soil enzyme activities of paddy soilAs compared with conventional tillage, treatments of no-tillage increased activities of sucrase, urease, protease, catalase, polyphenol oxidase in0-5cm soil layer, and between SNT and CNT, the most increased range was SNT, but reduced activities of sucrase, urease, protease, catalase, polyphenol oxidase in0-5cm soil layer, and between SNT and CNT, the least reduced range was CNT.9. Influence of no-tillage on soil microorganism quantity of paddy soilAs compared with conventional tillage, treatments of no-tillage increased quantity of fungus, actinomyces in0-5cm soil layer, and between SNT and CNT, the most increased range is SNT. Treatments of no-tillage reduced quantity of bacteria, fungus, actinomyces, anaerobic nitrogen-fixing bacteria, aerobic cellulose decomposing bacteria, anaerobic cellulose decomposing bacteria in5-20cm soil layer, and between SNT and CNT, the least reduced range is CNT. The quantity of ammonifying bacteria in0-20cm soil layer, quantity of fungus and actinomyces in5-12cm soil layer of SNT were more than other treatments.Therefore, the effects of SNT on growth, yield, nitrogen utilization of rice and soil fertility properties are superior to those of CNT.更多还原