【作者】 刘汝亮；

【导师】 杨正礼； 李友宏；

【作者基本信息】 中国农业科学院 ， 农业生态学， 2013， 博士

【摘要】 在提高氮肥利用效率和保证作物稳产高产条件下，减少农田氮素流失和对环境的压力，协调好粮食、资源和环境间的矛盾，是农业可持续发展面临的重要课题。宁夏引黄灌区水稻种植集约化程度高，因不合理施肥引起的农田面源污染较为严重。稻田淋洗损失是灌区氮素损失的主要途径，但稻田生态系统中氮素淋洗特征和过程控制技术研究尚未引起重视。因此，开展引黄灌区稻田退水污染特征与过程控制技术研究具有重要的科学价值和现实意义。2010-2012年，分别布置了两种类型试验。利用室内土柱模拟试验，研究了常规施肥(N₃₀₀)、优化施肥(N₂₄₀)和2倍施氮量(N₆₀₀、N₄₈₀)处理条件下氮素在灌淤土中的迁移和淋失特征，并对不同形态氮素的累积淋失过程进行了拟合。同时，针对灌区稻田施肥环节存在的关键问题，从“源头合理减量和肥料高效利用”两个方面切入，对稻田氮素淋失过程控制技术进行了系统研究。利用田间小区试验，以常规施肥为对照，研究了缓释肥侧条施肥（低肥、中肥和高肥）、控释氮肥育苗箱全量施肥（中氮和高氮）和氮肥后移（3-4次）对水稻产量、氮肥利用率、氮素淋失和氮平衡的影响特征。取得以下主要研究结果：（1）土柱模拟试验表明：不同施肥处理下淋洗液中NO₃^--N浓度呈先升高后降低的趋势，淋洗峰值出现时间随施氮量增加后移。N-240、N₃₀₀、N₄₈₀和N₆₀₀处理NO₃^-N累积淋失量分别为68.37、86.22、146.26和170.68kg/hm²，占施氮量的比例分别为28.49%、28.74%、30.47%和28.45%。NO₃^--N是氮素淋洗损失的主要形态。NO₃^--N累积淋失量Y_t与淋洗时间t（d）的拟合结果发现，N0、N₂₄₀和N₃₀₀处理以对数方程Y_t=a+blnt的拟合效果最好（R²=0.897-0.915），随着施氮量增加，N₄₈₀和N₆₀₀处理则以幂函数方程lnY_t=a+blnt的拟合效果最好（R²=0.917-0.913）。NH₄⁺-N的淋失主要发生在淋洗前期。各施肥处理NH₄⁺-N累积淋失量分别为18.60、25.07、37.77和45.96kg/hm²，占施氮量的比例分别为7.75%、8.36%、7.87%和7.66%。NH₄⁺-N累积淋失量Y_t与淋洗时间t（d）的拟合服从对数方程Y_t=a+blnt（R²=0.898-0.966）。N₂₄₀、N₃₀₀、N₄₈₀和N₆₀₀处理总氮淋失量分别为94.53、128.02、222.06和268.6kg/hm²，占施氮量的比例分别为39.38%、42.67%、46.26%和44.77%。施入灌淤土的氮肥有33.76%～46.26%通过淋洗损失。各施肥处理总氮累积淋失也都服从对数方程Y_t=a+blnt（R²=0.927-0.975）。NO₃^--N淋失占总氮淋失量的62.40%～66.87%，NH₄⁺-N占15.45%～16.55%，约20%左右的氮素以溶解性有机态的形式淋失。淋洗结束后，NO₃^--N残留高峰在0～20cm土层，NH₄⁺-N主要累积在20～40cm土体中。（2）田间小区试验表明：与常规施肥相比，侧条施肥、育苗箱全量施肥和氮肥后移处理下，施氮量降低20%～60%，水稻产量没有显著降低，但显著提高了氮肥生产效率和利用率。侧条施肥高肥处理（N176kg/hm²）氮肥偏生产力为49.3kg/kg，显著高于常规施肥处理的29.8kg/kg；育苗箱全量施肥高氮处理（N120kg/hm²）和氮肥后移N₂₄₀/3（分3次施肥）处理的氮肥利用率分别比常规施肥处理提高了20.7%和8.0%。稻田氮素流失的关键控制期：以尿素为氮源，施肥后9d内是防止氮素流失的关键时期，侧条施肥处理30d内氮素都有流失的风险，育苗箱全量施肥田面水总氮浓度显著低于常规施肥处理，流失风险较低。常规施肥处理氮素的淋洗损失主要发生在水稻拔节期之前，侧条施肥、育苗箱全量施肥和氮肥后移处理淋失高峰后移至分蘖－开花期。NO₃^--N是氮素淋失的主要形态，常规施肥处理的NO₃^--N净淋失量占总氮流失量的66.3%。侧条施肥高肥处理、育苗箱全量施肥高氮处理和氮肥后移N240/3处理的总氮净淋失量分别比常规施肥处理减少了11.75、30.46和14.64kg/hm²，淋失率分别比常规施肥处理降低了44.5%、51.8%和52.5%。侧条施肥高肥处理、育苗箱全量施肥高氮处理和氮肥后移N₂₄₀/3处理的总氮淋失量占施氮量的比例分别为7.93%、23.7%和6.74%，常规施肥处理平均比例为12.8%。（3）稻田氮素损失的途径分析：水稻收获后，土体中Nmin累积量显著低于播前水平，且向下淋洗趋势明显。常规施肥处理氮素表观损失量平均高达176.4kg/hm²，表观损失率为57.7%；侧条施肥处理氮素表观损失率为19.6%～35.1%，育苗箱全量施肥各处理表观损失率为30.8%～35.1%，氮肥后移各处理表观损失率为32.2%～49.0%。以尿素和缓控释肥为氮源，氮素淋失量占表观损失量的比例分别为20%和50%左右，其余以氨挥发和反硝化途径损失。综合考虑水稻产量和环境效益，侧条施肥高肥处理、育苗箱全量施肥高氮处理、氮肥后移N240/3处理可作为减少稻田氮素流失的控制技术。更多还原

【Abstract】 It is an important subject for the sustainable agriculture development to improve nitrogen fertilizeruse efficiency and ensure crop high-yield stability, and then reduce nitrogen loss from farmlands andnegative effect on the environment, and need to coordinate the conflict between food safety, resourcesand environment. Due to the high intensive cultivation of paddy rice in the Yellow River Irrigated Areaof Ningxia, it causes even severe non-point source pollution by unreasonable fertilization and irrigationin the farmlands. Nitrogen leaching losses is the main nitrogen loss pathway, however, these researcheson the characteristics of nitrogen leaching losses and mechanisms of process controlling are notconcerned very much in the paddy rice farmland ecosystem. Therefore, it has important scientific andrealistic significance to study on the characteristics of water pollution in paddy rice field and thecontrolling technology of pollutant in the Yellow River Irrigated Area of Ningxia.There were two different kind of experiments conducted from2010to2012. The soil columnsimulation experiment in a laboratory was used to study the characteristics of soil nitrogen movementand leaching in Irrigation Silting Soils with these treatments of conventional fertilization (N₃₀₀),optimize fertilization (N₂₄₀), and twice as much as the nitrogen fertilizer rates (N₆₀₀, N₄₈₀), and theaccumulated leaching process of different form of nitrogen were fitted with the equations. The fieldin-situ experiment was carried out to study the effects of side bar fertilization （low fertilizer rate, middlefertilizer rate and high fertilizer rate）, seeding-box fertilization （middle N rate and high N rate）, andpostponing N application （topdressing by3⁴times） in contrast to conventional fertilization on the riceyield, nitrogen fertilizer use efficiency, nitrogen leaching loss and apparent nitrogen balance. The mainresults are as following:（1） Soil column simulation experiment indicated that NO₃^--N concentrations in leachate withdifferent fertilization treatments were increased firstly and then decreased, the leaching peak arose delaywith nitrogen rates increasing. The accumulated NO₃^--N leaching amounts were68.37,86.22,146.26,and170.68kg/hm²in treatments N₂₄₀, N₃₀₀, N₄₈₀, and N₆₀₀, which accounted for nitrogen fertilizerapplication rates by28.49%,28.74%,30.47%, and28.45%, respectively. NO₃^--N was the predominantnitrogen leaching form, and accumulated NO₃^--N leaching amount Y_tand leaching time t（d） can befitting use equation, which could be described by the logarithmic equation of Y_t=a+blnt in treatmentsN0, N₂₄₀, and N₃₀₀; with nitrogen application rate increasing, the power function equations of lnY_t=a+blnt were found in treatments N₄₈₀and N₆₀₀.NH₄⁺-N leaching loss occurred in the earlier period. The accumulated NH₄⁺-N leaching amountwere18.60,25.07,37.77, and45.96kg/hm²in treatments N₂₄₀, N₃₀₀, N₄₈₀, and N₆₀₀, which accountedfor nitrogen fertilizer application rates by7.75%,8.36%,7.87%, and7.66%, respectively. Theaccumulative NH₄⁺-N leaching amount and leaching time t（d） was submit to the logarithmic equation ofY_t=a+blnt.Total N leaching losses were94.53,128.02,222.06, and268.6kg/hm²in treatments N₂₄₀, N₃₀₀, N480, and N600, which accounted for nitrogen fertilizer application rates by39.38%,42.67%,46.26%,and44.77%, respectively. About33.76%⁴6.26%of fertilizer nitrogen applied in soil was lost byleaching. The accumulative total N leaching amount can be fitting use logarithmic equation of Y_t=a+blnt.NO₃^--N leaching amount accounted for total N was ranged from62.40%to66.87%, and NH₄⁺-N tototal N was ranged from15.45%¹6.55%, about20%of nitrogen leaching by dissolved organicnitrogen form. After the leaching experiment, NO₃^--N residual peak in the0²0cm soil, but NH₄⁺-Nmainly accumulated in20⁴0cm soil.（2） The field in-site experiment showed that rice yields were not significantly decreased withtreatments side bar fertilization, seeding-box fertilization, and postponing N application comparing withtreatment conventional fertilization, however, there were20%⁶0%of nitrogen fertilizer rate reductionand significantly improved nitrogen fertilizer production and use efficiency.Partial factor productivity from applied nitrogen in treatment side bar fertilization of high fertilizerrate （N176kg/hm²） was49.3kg/kg, which was significantly higher than29.8kg/kg in treatmentconventional fertilization. Nitrogen fertilizer use efficiency in treatments seeding-box fertilization ofhigh N rate （N120kg/hm²） and postponing N application of N240/3（topdressing by3times） wasincreased by20.7%and8.0%in contrast to treatment conventional fertilization, respectively.The key control stage of nitrogen leaching in paddy rice field: as nitrogen source, during the first9days after urea fertilizer application is a critical period to prevent nitrogen leaching loss; there alwayshigh risk of leaching loss within30days after transplanting with the side bar fertilization treatment;however, the surface water total N concentration in treatment seeding-box fertilization was significantlylower than that in treatment side bar fertilization, and the risk of loss was lower.The nitrogen leaching mainly occurred before the rice jointing stage in treatment conventionalfertilization, but the leaching peak shift after the tiller-flowering stage in treatments side barfertilization, seeding-box fertilization, and postponing N application. NO₃^--N is the main form ofnitrogen leaching loss, NO₃^--N leaching amount accounted for total N by66.3%in treatmentconventional fertilization. Compared with treatment conventional fertilization, the net total N leachingamount were declined by11.75,30.46, and14.64kg/hm²in treatments side bar fertilization,seeding-box fertilization, and postponing N application, the leaching ratio decreased by44.5%,51.8%and52.5%, respectively. Total N leaching amounts accounted for nitrogen fertilizer application ratewere7.93%,23.7%and6.74%in treatments side bar fertilization of high fertilizer rate （N176kg/hm²）seeding-box fertilization of high N rate （N120kg/hm²） and postponing N application of N240/3,respectively. The average total N leaching rates in treatment conventional fertilization was12.8%.（3） Nitrogen loss way in the paddy rice field: After the rice harvest, the soil Nminaccumulation wassignificantly lower than the level before transplanting and evidently leaching downward. The averageapparent loss amount was176.4kg/hm²and was57.7%in treatment conventional fertilization, and theapparent nitrogen loss rate were19.6%～35.1%,30.8%～35.1%, and32.2%～49.0%in treatments sidebar fertilization, seeding-box fertilization, and postponing N application, respectively. Use urea as nitrogen source, the proportion of nitrogen leaching loss amount account for the apparent loss by about20%, use slow/control-released fertilizer as the nitrogen source, the proportion of nitrogen leaching lossamount account for the apparent loss of about50%, and the remaining losses by ammonia volatilizationand denitrification.Considering the rice yield and environmental benefits, these could be scientific process controltechnology for reduction of nitrogen losses in the paddy field with treatments side bar fertilization ofhigh N rate （N176kg/hm²）, seeding-box fertilization of high N rate （N120kg/hm²）, postponing Napplication of N240/3.更多还原