【作者】 梁斌；

【导师】 周建斌；

【作者基本信息】 西北农林科技大学 ， 植物营养学， 2012， 博士

【摘要】 长期以来，我国农业生产中主要依靠有机肥来供应作物养分，维持土壤肥力。自上世纪五六十年代以来，农田中化肥的施用量逐年增加，有机肥所占的比例越来越低。化肥在粮食增产方面发挥了巨大的作用，但化肥特别是氮肥的施用也带来一系列的环境问题，给农田生态安全和人类健康带来威胁。随着我国养殖业的迅速发展，产生的畜禽粪便越来越多，如何有效处置这些有机物料，是我们面临的另一环境问题。土壤施用是处置这些有机物料的有效方式。关于有机肥与无机肥配施在提高作物产量和土壤肥力效果方面已有大量研究，但关于有机肥与化肥长期配施，协调土壤氮素供应机理的研究尚待深入。施用有机肥同时供应了土壤微生物所需能源物质和营养物质，进而可影响土壤碳、氮转化过程。因此，揭示有机肥与化肥长期配施在调控土壤氮素供应方面的机理，以协调土壤供氮与作物需氮的关系对于保障粮食生产，减少化学氮肥施用，提高氮肥利用率，减少环境污染，维持农业可持续发展等方面具有重要的理论及实践意义。本研究以经19年不同施肥处理土壤（No-F，长期不施肥；NPK，长期施用化肥；MNPK，长期有机肥配施化肥）为研究对象，利用室内培养试验、盆栽试验和田间15N微区试验相结合的方法，研究了长期不同施肥对土壤特性（主要为可溶性有机氮、有机碳稳定性和晶格固定态铵）的影响，以及不同施肥土壤对肥料氮固持及利用的影响，获得以下主要结论：（1）通过室内培养的方法，研究了长期不同施肥土壤对氮素生物和非生物固持的影响。结果表明，施入铵态氮使No-F、NPK和SNPK（秸秆还田配施化肥）土壤晶格固定态铵分别显著提高9.2%、7.4%和8.0%，占所施入氮肥的20%、17%和9%，而对MNPK土壤晶格固定态铵无显著影响。施入硝态氮和铵态氮后，分别有0¹0%和20⁶0%所施氮素发生固持，铵态氮的固持量显著高于硝态氮。铵态氮的固持率与其硝化率呈极显著负相关关系，说明硝化作用的进行减少了铵态氮的固持，长期有机肥配施化肥降低了土壤粘土矿物对铵态氮的晶格固定。（2）利用室内培养的方法，研究了供应有效碳（葡萄糖）和有效氮（硫酸铵）对不同施肥土壤氮素固持及土壤有机碳降解的影响。结果表明，MNPK土壤粘土矿物固持了3.8%所施入的氮素，显著低于No-F（14.1%）和NPK（9.5%）土壤，进一步证明长期有机肥配施化肥降低土壤对铵态氮的晶格固定能力。加入有效碳源显著增加各土壤微生物量氮含量，土壤微生物量氮的增加量占氮素固持量的30⁵3%，两者呈极显著正相关关系。培养期间MNPK土壤有机碳的降解率为3.3%，显著低于No-F和NPK土壤（4.4%和4.2%）；施用化学氮肥使No-F、NPK和MNPK土壤有机碳降解率分别显著提高54%，35%和21%。说明长期有机肥配施化肥增加了土壤有机碳的稳定性，施用化学氮肥促进各土壤有机碳的降解，增加了CO₂的释放。（3）利用15N示踪技术研究了盆栽条件下氮肥（尿素）及其与秸秆配施（尿素氮和秸秆氮按1:1配施）在长期不同施肥土壤中的固持与供应特性。结果表明，与不施氮肥对照相比，单施尿素对No-F处理土壤小麦产量无影响，显著提高NPK和MNPK处理土壤小麦产量。单施尿素处理拔节期MNPK和NPK土壤分别有62%和58%施入的氮发生固持；而后，固持的氮素重新释放供小麦吸收利用，拔节期后小麦吸收的氮素分别有99%和74%源于前期固持氮素的释放。MNPK处理土壤氮肥利用率（61%）显著高于NPK（50%）和No-F（23%）处理土壤。与单施尿素处理相比，尿素与秸秆配施显著降低小麦产量和氮肥利用率，但MNPK处理小麦产量及氮肥利用率仍显著高于NPK处理。小麦收获时秸秆与尿素配施处理不同施肥处理土壤中仍有60%以上的尿素氮固持在土壤中。以上说明长期有机肥配施化肥增加作物生长前期氮素的固持，随后被固持的氮素发生释放供作物吸收利用，协调土壤氮素供应，从而提高作物产量及氮肥利用率；尿素氮和秸秆氮按1:1配施，在当季作物生长期间大部分氮素固持在土壤中，影响当季作物氮素吸收和作物产量。（4）利用15N标记田间微区试验，研究了氮肥在小麦—休闲旱作制度下长期不同施肥处理土壤中的固持、吸收及损失情况。结果表明，在小麦拔节期，MNPK土壤有15.3%氮肥被微生物固持，显著高于NPK土壤（12.6%）；从小麦拔节期到开花期，MNPK和NPK土壤中被固持的氮素分别有82%和69%重新释放供作物吸收利用。No-F土壤小麦吸氮量和微生物对氮素固持量均较低，小麦收获时有超过30%的氮肥被淋溶到20cm土层以下，氮肥利用率仅为20%；而NPK和MNPK土壤氮肥利用率分别为61%和65%。小麦收获后，氮肥在No-F、NPK和MNPK土壤的回收率（作物吸收+土壤残留）分别为90%、97%和91%。经夏季休闲，氮肥在三土壤的回收率分别为57%、89%和86%，长期不施肥土壤氮素损失显著高于施肥土壤。可见，长期有机肥配施化肥可较好的协调土壤氮素供应和作物需氮的关系，提高氮肥利用率，减少氮素损失；在小麦-休闲种植制度下，本地区低肥力土壤中氮肥的损失主要发生在夏季休闲期间。（5）通过15N标记田间微区试验，研究了氮肥在小麦—玉米轮作制度下长期不同施肥处理土壤的固持、吸收及损失的特性。结果表明，在小麦拔节期NPK和MNPK土壤分别有10%和14%氮肥被微生物固持，随后被固持的氮素有71%和84%发生释放供小麦吸收利用。MNPK土壤氮肥的利用率为62%，显著地高于NPK土壤（50%）及No-F土壤（仅为13%），MNPK土壤小麦产量也显著高于NPK和No-F土壤。小麦收获后残留在No-F、NPK和MNPK土壤0-100cm剖面的氮肥分别占施用量的88%、45%和38%，残留氮中矿质态氮所占的比例分别为67%、23%和4%。No-F、NPK和MNPK土壤中残留的肥料氮分别有11%、13%和5%被后茬玉米吸收利用，说明小麦季残留的肥料氮的有效性与其残留量及形态有密切关系。小麦—玉米轮作结束时，No-F、NPK和MNPK土壤氮肥的总回收率分别为45%、83%和85%。进一步说明，长期有机肥配施化肥协调了土壤氮素的固持与释放，进而提高小麦产量和氮素利用率，减少氮肥损失。（6）通过（15）^N标记微区试验，研究了长期不同施肥和作物不同生长阶段对土壤可溶性有机氮含量的影响。结果表明，农田耕层（0-15cm）土壤可溶性有机氮的含量范围为7.5²9.3mg kg^-1，占可溶性总氮的13⁷6%。40-100cm剖面土壤可溶性有机氮占可溶性总氮的比例为40⁵7%。长期有机肥配施化肥显著提高0-15cm土层土壤可溶性有机氮含量，土壤可溶性有机氮占可溶性总氮的比例达60%。小麦开花期各土壤耕层可溶性有机氮的含量显著高于拔节期和收获期。（15）^N测定发现，耕层土壤有0.4².8%可溶性有机氮来源于施入的肥料氮，说明有少量肥料氮转化为土壤可溶性有机氮。可见农田土壤可溶性有机氮含量较高，其在土壤中的行为值得关注。综上可见，增强土壤对氮素的生物固持及释放，提高土壤对氮肥的缓冲能力，进而协调了土壤供氮与作物需氮的关系，是有机肥与化肥长期配施处理提高作物产量、氮肥利用率的重要机理之一；长期有机肥配施化肥还提高了土壤有机碳的稳定性，有利于增加土壤固碳，减少温室气体排放。本研究中长期有机肥配施化肥处理化肥氮量的施用量仅为单施化肥处理的30%，化肥氮用量明显降低。因此，长期有机肥配施化肥在保障粮食生产、维持农业可持续发展方面作用重大。更多还原

【Abstract】 Traditionally, manure was used for maintaining soil production in China. However, theapplication of manure to agricultural fields has declined since the1980s due to the increasinguse of inorganic fertilizers. Since the1950s, the increasing production of fertilizersdramatically has increased the agricultural productivity in most regions of the world.Meanwhile, the use efficiency of fertilizers is decreasing, especially for nitrogen. A high inputcombined with a low efficiency ultimately resulted in environmental problems, such as soildegradation, eutrophication, pollution of groundwater, and emission of ammonia andgreenhouse gases. In recent years, continuous and steady development of livestock breedinghas brought great impaction on natural environment. How to deal with the manure in thelivestock breeding is another challenge for us. Application of these manure to soil is awin-win way. It not only reduces the no point pollution of manure, but also improves soilfertility and increased crop yield. Application of manure affected theimmobilization-remineralization turnover （MIT） of N in soil. The researches about the effectsof manure on the MIT of N in agriculture were almost short-term （about1³years）. Fewexperiments have been conducted properly to test the long-term effects of the addition ofmanure on the MIT of N.Therefore, three long-term fertilized soils （No-F, no fertilization; NPK, applied inorganicNPK fertilizers; and MNPK, applied manure plus inorganic NPK fertilizers） sampled from a19-year field trial were used to study the effects of long-term different fertilizationmanagements on the MIT of N, the yield of crop, the use, residue and loss of N fertilizer,stabilization of soil organic C in incubation, pot, and filed experiments. The main conclusionsfrom the study were as followed:（1） An incubation experiment was conducted to study the effect of long-term fertilizationmanagements on the abiotic and biotic immobilization of nitrogen. Addition of ammoniumincreased the fixed N in clay minerals by9.2%,7.4%, and8.0%in the No-F, NPK, and SNPK（straw plus NPK fertilizers） soils, and accounting for20%,17%, and19%of added N,respectively, but it had no effect on fixed N in the MNPK soil. After addition of ammonium, 20⁶0%of the added N was immobilized, the amount of immobilized N was only0¹0%after addition of nitrate. Nitrification rate and immobilization rate of added ammonium weresignificantly correlative. Therefore, we concluded that long-term application of manure plusinorganic fertilizers reduces the ammonium fixation by clay minerals, and the nitrificationdecreased the immobilization of ammonium.（2） Two short-term incubation experiments were conducted to assess the impact ofadding available nitrogen （NH4） and C （glucose） on NH4fixation by clay minerals, and thedecomposition of SOC in these soils. The NH4fixed by clay minerals in the MNPK soils（3.8%of added N） was significantly lower than that in the No-F, and NPK soils （14.1%, and9.5%of added N）. After addition of available C, the increased soil microbial biomass Naccounted for30⁵3%of the amount of immobilized N, and the both were significantlycorrelative. The decomposition rate of SOC in the MNPK soil （3.3%） during the incubationwas significantly lower than in the No-F, and NPK soils （4.4%, and4.2%）. Addition of NH₄significantly increased the decomposition of SOC in different soil treatments, and the MNPKsoil also had lower decomposition rate than the No-F, and NPK soils. We concluded thatlong-term combined application of manure and NPK fertilizers reduces the NH4fixation byclay minerals, and improves the stabilization of soil organic C.（3） A pot experiment was conducted to evaluate the effect of long-term differentfertilization managements on N retention and supply in soils after the addition of urea-N aloneor combined with straw. Addition of N fertilizer had no effect on grain yield of wheat in theNo-F soil, while it significantly increased grain yield of wheat in the NPK and MNPK soils.In the treatment of addition of urea-N alone,62%and58%of added N was immobilized inthe NPK and MNPK soils at elongation time of wheat. After elongation time,99%and74%of the assimilated N by wheat were from the remineralization of the immobilized N,respectively. When urea-N was added alone, the use efficiency of the urea-N in the MNPKsoils was as high as61%, and it significantly higher than in the NPK （50%） and the No-Fsoils （23%）. Grain yield of wheat in the MNPK soil was also significantly （P<0.05） higherthan that in the NPK and No-F soils. Compared with addition of urea-N alone, the combinedaddition of straw and urea-N significantly decreased grain yield and N use efficiency. For theMNPK soil, the N use efficiency was only11%, it was still significantly higher than that ofNPK soil. After wheat harvest,59⁶6%of added urea-N in the treatment of combinedaddition of inorganic N and straw was still immobilized in the soil. We concluded thatlong-term application of manure plus NPK fertilizers has a high ability to modulate the Nsupplying of soil by adjusting the N retention and release processes, and increases grain yieldand N use efficiency. （4） We investigated the fates of15N-labeled fertilizer in three long-term differentfertilized farmlands under wheat-fallow cropping system. The15N use efficiency （NUE） in theNo-F soil was only20%; the majority of15N remained in soil after harvest. This compared toa NUE of60%and65%in the NPK and MNPK soils, respectively. The immobilized15N bymicroorganisms in the MNPK soil during the early stage of wheat growth was significantlyhigher than in the NPK soil （15.3%compared to12.6%of the added N）; Of the Nimmobilized83%in the MNPK and69%in the NPK was released during the elongation andflowering stage of wheat. In comparison with NPK, the MNPK soil had significantly higher（P<0.05） grain yield （11t ha-1compared to8t ha-1）. During the summer fallow,33%,8%,and5%of15N was lost from the No-F, NPK, and MNPK soils, respectively. Our findingshighlight that the importance of applying manure with inorganic fertilizers to modulating soilN retention and supply to increase N use efficiency and grain yield while minimizing N loss.（5） Using15N tracer techniques, this study examined how long-term different fertilizationmanagements influence the N use efficiency and leaching through altering the MIT of N. Atwheat stem elongation,14%of the15N was immobilized by microorganisms of the MNPKsoil compared with10%in the NPK soil.70%in the NPK soil and84%in the MNPK soil ofthe immobilized15N was mineralized between stem elongation and flowering; almost all ofthese was taken up by the wheat. The15N use efficiency of wheat was62%in the MNPK soil,50%in the NPK soil, and13%in the No-F soil. Mineral N concentrations in the No-F soilwere high and more than50%of the15N was leached below the20cm depth at wheat harvest.Nearly88%of the15N-fertilizer remained in the0-100cm depth of the No-F soil after wheatharvest compared with45%in the NPK soil and38%in the MNPK soil. After wheat harvest,the total recovery rate of15N-fertilizer was101%in the No-F,95%in the NPK soil, and100%in the MNPK soil. The succeeding maize crop took up11%of the residual15N in the No-Fsoil,13%of the residual15N in the NPK soil, and5%of the residual15N in the MNPK soil.The total recovery rate of15N-fertilizer after maize harvest was45%for the No-F soil,83%for the NPK soil, and85%for the MNPK soil. We conclude that the long-term combinedapplication of manure and NPK fertilizers can affect MIT in soil and improve synchronybetween the N supply and crop demand.（6） Using15N tracer techniques, a microplot experiment in the field was conducted toinvestigated the effect of long-term different fertilization managements and short-termaddition of N on content of water extractable organic N （WEON） during growth of wheat inwheat-fallow monoculture and wheat-maize rotation cropping systems. The WEON contentwas7.5²9.3mg kg-1, and accounted for13⁷6%of the total extractable N. In the40-100cmsoil layers, the accumulated WEON accounted for40⁵7%of the accumulated total soluble N. Long-term application of manure plus inorganic NPK fertilizers significantly increasedWEON in0-15cm soil layer, the ratio of WEON to total soluble N was about60%. Thepercent and amount of WEON at the flowering was the highest during growth of wheat.0.4².8%of the soil extractable organic N was derived from the15N-labeled fertilizer. Weconclude that WEON is a significant pool within agriculture soils, long-term application ofmanure plus inorganic NPK fertilizers increased the WEON content in the topsoil, and a partof the added N before seeding wheat converted to water extractable organic N in soil.In general, long-term application of manure plus NPK fertilizers increase crop yield andN use efficiency, which can partly be attributed to the MIT of N improving buffer capacity ofsoil and synchronizing N supply of soil and N demand of crop; furthermore, long-termapplication of manure plus NPK fertilizers improves the stability of soil organic C whichhelps to increase C sequestration; in addition, the rate of inorganic N fertilizer in the treatmentof long-term application of manure plus NPK fertilizers is only30%of the rate of N fertilizerin the treatment of application inorganic NPK fertilizers. Hence, long-term application ofmanure plus inorganic NPK fertilizers is an useful way for food production security andsustainable agriculture.更多还原