Non-Point Pollution from Crop Production： Global,Regional and National Issues

China is now the world＇s largest producer and user of industrial fertilizers and manures. Consequently China plays a substantial role in global N cycle dynamics and in man＇s disruption of the nitrogen cycle though there are still significant uncertainties about the size and importance of emission and leaching rates. A major cause of China＇s global role is the overuse of nitrogen fertilizers, which is most serious with intensive vegetable production where application rates can be up to 50% greater than crop needs, but is also a problem with wheat, rice and maize. China＇s overuse of nitrogen fertiliser over the past 10-20 years has resulted in non-point source （NPS） pollution from crop production becoming a major cause of water pollution, and the situation is projected to get worse. In contrast, water pollution from point sources such as intensive livestock production and urban or industrial development is being brought more under control. The consequences for air pollution are equally serious. Emissions of nitrous oxide from fertilizers and manures may be so large that China could be responsible for 25-30% of global emissions of this damaging greenhouse gas and of the global warming resulting from it. The main national and local issues relate particularly to low fertilizer use efficiency and the losses of ammonia and NOx that lead to acid precipitation, and leaching and run-off losses that result in high nitrate levels in groundwater and eutrophication of rivers and lakes. The reasons why farmers overuse nitrogen fertilizer are complex and not fully understood. They involve agro-climate differences between provinces and counties, farming systems and farm income structures. Although there is a wide range of institutional and technological improvements that can greatly reduce this overuse rapid progress in reducing NPS is unlikely.     

半干旱地区土壤水分和养分对玉米生长和产量的耦合影响

Interaction between soil water and nutrients plays an important role in sustainable crop management in semi-arid environments.On the basis of a field experiment conducted from 2000 to 2003,this study examined the coupled effects of irrigation and fertilizers on maize growth and yield in a semi-arid region of northeastern China.In terms of plant productivity,nitrogen fertilizer had the most significant effect followed by irrigation and phosphate levels.The combined application of nutrients and irrigation exerted a synergistic effect on the grain yield of maize plants.Regression analysis indicated that optimal levels of nitrogen and phosphate,in addition to adequate irrigation,could greatly improve the efficiency of grain production.Similarly,optimization of soil nutrient availability substantially increased water use efficiency.These suggested that for the most efficient and sustainable crop production,irrigation and nutrient management should be based on a quantitative understanding of water/nutrients interaction,particularly in semi-arid and arid regions.     

中国化肥使用带来的环境问题

The current status of chemical fertilizers production and consumption in China as well as their important roles in Chinese modern agriculture are discussed with special concerns to the environmental issues related to chemical fertilizer use.On the one hand.the total amount of chemical fertilizer produced is insufficient to meet the agricultural needs.On the other hand.the production and consumption of chemical fertilizers in China are obviously not balanced.In some areas over application of nitrogen fertilizers and loss of phosphate fertilizer due to soil erosion have resulted in some undesirable environmental problems such as increase of nitrate in water and eutrophication of water bodies.Maximum scientific uses of organic manures in combination with reasonable use of chemical fertilizers are part of good practices not only in increasuing soil productivity and keeping sustainable agriculture development but also in minimizing their detrimental effects on the environment.     

中国洞庭湖区稻田土壤氮素淋溶损失的系统研究

A two-year lysimeter study was conducted to study the effects of different fertilizers and soils on nitrogen leaching loss in a double rice cropping system by considering three major types of paddy soils from the Dongting Lake area. The results showed that N concentration in the leachate did not differ significantly among the treatments of urea, controlled release N fertilizer and pig manure and that all these fertilizers produced higher total nitrogen (TN) concentrations in the leachate compared to the case where no fertilizer was applied. The TN leaching loss following urea treatment accounted for 2.28%, 0.66%, and 1.50% of the amount of N applied in the alluvial sandy loamy paddy soil (ASL), purple calcareous clayey paddy soil (PCC), and reddish-yellow loamy paddy soil (RYL), respectively. Higher TN loss was found to be correlated with the increased leachate volume in ASL compared with RYL, and the lowest TN loss was observed in the PCC, in which the lowest leachate volume and TN concentration were observed. Organic N and NH4+ -N were the major forms of N depleted through leachate, accounting for 56.8% and 39.7% of TN losses, respectively. Accordingly, soil-specific fertilization regimens are recommended; in particular, the maximum amount of fertilizer should be optimized for sandy soils with a high infiltration rate. To avoid a high N leaching loss from rice fields, organic N fertilizers such as urea or coated urea should primarily be used for surface topdressing or shallow-layer application and not for deep-layer application.     

控制中国非点源污染的生物经济学战略

While non-point pollution from agriculture has become an increasingly serious problem in China, some progress has been made in studying the causal biophysical processes. However, few studies have assessed the economic consequences of non-point pollution in China or the policy options that could be employed to combat it. In this work a sustainable strategy to control non-point pollution from crop production, which involved taxing excessive inputs of irrigation water and fertilizer, was proposed. The approach taken to assess these measures combined biophysical and economic models,having a trade-off between economic returns and an improved environment. A proven and practical spatially referenced water and nutrient management model was used to determine the quantities of excessive irrigation water and fertilizer for specific soil and land use. Also, a set of indicators were proposed for evaluating the effects of agricultural economic output and agricultural practices on the environment.     

1970-2030年精细农业耕作体系下全球和区域性氮素的表面平衡研究

Global nitrogen (N) budgets for intensive agricultural systems were compiled for a 0.5 by 0.5 degree resolution. These budgets include N inputs (N fertilizer, animal manure, biological N fixation and atmospheric N deposition) and outputs (N removal from the field in harvested crops and grass and grass consumption by grazing animals, ammonia volatilization, denitrification and leaching). Data for the historical years 1970 and 1995 and a projection for 2030 were used to study changes in the recovery of N and the different loss terms for intensive agricultural systems. The results indicated that the overall system N recovery and fertilizer use efficiency slowly increased in the industrialized countries between 1970 and 1995, the values for developing countries have decreased in the same period. For the coming three decades our results indicated a rapid increase in both the industrialized and developing countries. High values of > 80% for fertilizer use efficiency may be related to surface N balance deficits, implying a depletion of soil N and loss of soil fertility. The projected intensification in most developing countries would cause a gradual shift from deficits to surpluses in the coming decades. The projected fast growth of crop and livestock production, and intensification and associated increase in fertilizer inputs would cause a major increase in the surface N balance surplus in the coming three decades. This implied increasing losses of N compounds to air (ammonia, nitrous oxide and nitric oxide), and groundwater and surface water (nitrate).     

上海郊区蔬菜田氮素流失的研

Nitrogen （N） leaching in vegetable fields from December 2002 to May 2003 with equal dressings of total N for a sequential rotation of Chinese flat cabbage （Brassica chinensis L. var. rosularis） and lettuce （Lactuca sativa L.） in a suburban major vegetable production base of Shanghai were examined using the lysimeter method to provide a scientific basis for rational utilization of nitrogen fertilizers so as to prevent nitrogen pollution of water resources. Results showed that leached N consisted mainly of nitrate N, which accounted for up to more than 90% of the total N loss and could contribute to groundwater pollution. Data also showed that by partly substituting chemical N （30%） in a basal dressing with equivalent N of refined organic fertilizer in the Chinese flat cabbage field, 64.5% of the leached nitrate N was reduced, while in the lettuce （Lactuca sativa L.） field, substituting 1/2 of the chemical N in a basal dressing and 1/3 of the chemical N in a top dressing with equivalent N of refined organic fertilizers reduced 46.6% of the leached nitrate N. In the twoyear sequential rotation system of Chinese flat cabbage and lettuce, nitrate-N leaching in the treatment with the highest amount of chemical fertilizer was up to 46.55 kg ha^-1, while treatment plots with the highest amount of organic fertilizer had only 17.58 kg ha^-1. Thus, partly substituting refined organic fertilizer for chemical nitrogen in the first two seasons has a great advantage of reducing nitrate-N leaching.     

Leaching and Transformation of Nitrogen Fertilizers in Soil After Application of N with Irrigation： A Soil Column Method

A soil column method was used to compare the effect of drip fertigation （the application of fertilizer through drip irrigation systems, DFI） on the leaching loss and transformation of urea-N in soil with that of surface fertilization combined with flood irrigation （SFI）, and to study the leaching loss and transformation of three kinds of nitrogen fertilizers （nitrate fertilizer, ammonium fertilizer, and urea fertilizer） in two contrasting soils after the fertigation. In comparison to SFI, DFI decreased leaching loss of urea-N from the soil and increased the mineral N （NH4^＋-N ＋ NO3^--N） in the soil. The N leached from a clay loam soil ranged from 5.7% to 9.6% of the total N added as fertilizer, whereas for a sandy loam soil they ranged between 16.2% and 30.4%. Leaching losses of mineral N were higher when nitrate fertilizer was used compared to urea or ammonium fertilizer. Compared to the control （without urea addition）, on the first day when soils were fertigated with urea, there were increases in NH4^＋-N in the soils. This confirmed the rapid hydrolysis of urea in soil during fertigation. NH4^＋-N in soils reached a peak about 5 days after fertigation, and due to nitrification it began to decrease at day 10. After applying NH4^＋-N fertilizer and urea and during the incubation period, the mineral nitrogen in the soil decreased. This may be related to the occurrence of NH4^＋-N fixation or volatilization in the soil during the fertigation process.     

太湖地区水稻最适宜施氮量研究

To determine the optimal amount of nitrogen(N) fertilizer for achieving a sustainable rice production at the Taihu Lake region of China,two-year on-farm field experiments were performed at four sites using various N application rates.The results showed that 22%-30% of the applied N was recovered in crop and 7%-31% in soils at the rates of 100-350 kg N ha 1.Nitrogen losses increased with N application rates,from 44% of the applied fertilizer N at the rate of 100 kg N ha 1 to 69% of the N applied at 350 kg N ha 1.Ammonia volatilization and apparent denitrification were the main pathways of N losses.The N application rate of 300 kg N ha 1,which is commonly used by local farmers in the study region,was found to lead to a significant reduction in economic and environmental efficiency.Considering the cost for mitigating environmental pollution and the maximum net economic income,an application rate of 100-150 kg N ha 1 would be recommended.This recommended N application rate could greatly reduce N loss from 199 kg N ha 1 occurring at the N application rate of 300 kg N ha 1 to 80-110 kg N ha 1,with the rice grain yield still reaching 7 300-8 300 kg DW ha 1 in the meantime.     

中国南方大棚蔬菜地氮平衡与损失

High rates of fertilizer nitrogen (N) are applied in greenhouse vegetable fields in southeastern China to maximize production;however,the N budgets of such intensive vegetable production remain to be explored.The goal of this study was to determine the annual N balance and loss in a greenhouse vegetable system of annual rotation of tomato,cucumber,and celery at five N (urea) application rates (0,348,522,696,and 870 kg N ha-1 year-1).Total N input to the 0-50 cm soil layer ranged from 531 to 1 053 kg ha-1,and N fertilizer was the main N source,accounting for 66%-83% of the total annual N input.In comparison,irrigation water,wet deposition,and seeds in total accounted for less than 1% of the total N input.The fertilizer N use efficiency was only 18% under the conventional application rate of 870 kg N ha-1 and decreased as the application rate increased from 522 to 870 kg N ha-1.Apparent N losses were 196-201 kg N ha-1,of which 71%-86% was lost by leaching at the application rates of 522-870 kg N ha-1.Thus,leaching was the primary N loss pathway at high N application rates and the amount of N leached was proportional to the N applied during the cucumber season.Moreover,dissolved organic N accounted for 10% of the leached N,whereas NH3 volatilization only contributed 0.1%-0.6% of the apparent N losses under the five N application rates in this greenhouse vegetable system.     

丹麦畜禽粪肥利用对中国种养结合循环农业发展的启示

丹麦在畜禽养殖粪肥利用方面处于世界领先地位。丹麦完善的粪肥利用体系可做到种养平衡和按需施肥,在保证畜牧业健康发展的同时,也促进了种植业的发展。该文综述了丹麦粪肥利用与管理现状,重点分析了丹麦种养平衡生产模式和粪肥施用过程中氨减排技术,从科学理念、法规体系、先进技术和成熟模式等方面总结了丹麦畜禽养殖粪肥利用的成功经验,包括全过程污染控制的科学理念,详细量化、严格执行的管理政策法规,先进的粪肥利用关键技术装备,以及完善的粪肥利用模式,以期提高中国畜禽养殖粪肥利用水平,为推进中国种养循环农业发展提供借鉴。     

红枫湖流域非点源污染控制区划

非点源污染发生的广域性、分散性、随机性等特征使得对其进行效管控难度较大。以非点源污染关键源区识别为基础,对流域进行分区管控是实现非点源污染控制的有效途径。基于源头削减和过程管控协同管理的思路,将GIS技术、ArcSWAT模型、非参数检验和因子分析技术相结合,以农耕养殖程度较高的贵州红枫湖上游羊昌河流域为研究区,通过对流域近5 a非点源污染负荷特征进行模拟,识别影响非点源污染流失的关键因素,在此基础进行污染控制区划。结果表明：1）总氮和总磷负荷高风险区主要集中于地势较高且农业耕作活动频繁区域,刘官乡、黄腊乡、旧州镇及白云镇是非点源污染控制的重点乡镇;2）采用多因素方差分析7种不同因素对流域非点源污染负荷的影响程度表明,施肥量是影响总氮、总磷输出的最主要的因子,坡长、坡度及土地利用方式是次重要因子。针对羊昌河流域长期传统耕作以及化肥过量施用的现实特征来看,土壤有机磷的含量也会对总磷的输出产生一定的影响;3）羊昌河流域可划分为3个污染控制区,第1类：生态农业综合整治区（以近河道耕种区为主,面积254.4 km2）;第2类：污染治理区（农村生活及畜禽养殖区为主,面积405.74 km2）;第3类：生态修复区（高坡度强降雨区为主,面积464.47 km2）。研究结果可有效提升羊昌河流域非点源污染治理的效率,为水源地环境保护提供参考。     

中国稻田施氮技术研究进展

提高N肥利用率,加强稻田养分管理已经成为水稻生产中研究的热点。针对我国稻田N肥利用率低和N素损失严重的现状,综述了国内外提高稻田N肥利用率技术途径的研究进展,包括改进施肥方法(确定适宜施N量、N肥深施、前N后移、平衡施肥、有机与无机肥配施、水肥综合管理)、新型肥料的研制(硝化抑制剂、脲酶抑制剂、表面分子膜、缓控释肥)、计算机决策支持系统指导施肥和实时、实地N肥管理等。展望了今后需要加强研究的几方面工作。     

褐土区农田土壤氮磷淋溶特征及其管理措施

自20世纪90年代以来,持续过量氮磷化肥投入导致农业面源污染日益严重,了解农田土壤氮磷淋溶特征是降低地下水污染的基础。基于田间调查、长期定位肥料试验和田间试验,分析褐土区氮磷的盈余状况,阐明该区农田土壤氮磷的盈余变化、淋溶特征;评价田间管理措施对农田土壤氮磷淋溶的影响。结果表明,典型褐土区关中平原过量施氮的土壤达到83%以上,大量土壤硝态氮已经迁移到100cm土层以下,15%的水井地下水的硝态氮含量超过10 mg·L~(-1)(WHO饮用水标准);80%耕层土壤有效磷(Olsen-P)含量已超过20mg·kg-1,富磷土壤已出现可溶性磷素向耕层以下迁移的现象。氮肥和磷肥的投入量、氮磷吸收量和土壤氮磷残留量之间存在着3个发展阶段:环境友好-资源高效阶段、环境低风险-资源低效阶段和环境有害-资源无效阶段。与当地常规水肥投入量相比,在保证产量的前提下,化肥减量、降低灌溉量、施用生物炭或秸秆还田都可以降低氮磷淋失量;其中化肥减量、降低灌溉可显著降低氮磷的淋失,其次是施用生物炭和秸秆。施用秸秆条件下,阻控硝态氮淋失与微生物生物量碳氮的提高、土壤硝化势降低或反硝化势升高有关。此外,需要关注褐土区粮果复合系统中土壤氮磷淋溶的环境效应、地下水硝酸盐污染的溯源等问题。     

有机无机肥配施模式对氮素淋失的影响

为了探索农田氮素淋失低风险的有机无机肥配施模式,该研究收集了331个有效农田有机肥化肥配施数据对,分析了施肥总量、施肥结构（有机肥替代比）、施肥时间（基追施）、有机肥种类等因素对氮素淋失的总体影响。结果表明：与单施化肥相比,有机肥配施化肥中氮素总量较低时（N<200 kg/hm2）,农田总氮（Total Nitrogen,TN）、硝态氮（NO3--N）淋失分别减少36.77%、65.05%;有机肥替代比高于70%,虽然可减少TN淋失（39.64%）,但增加了溶解性有机氮（DON）淋失的风险（15.78%）,尤其是动物型有机肥替代化肥使DON淋失增加26.31%;氮肥基施可显著降低TN、NO3--N淋失（43.58%、70.51%,P<0.05）。碱性旱地土壤上有机肥配施化肥可有效抑制TN、NO3--N淋失,但增加了26.63%～42.95%的DON淋失。旱地氮素淋失以NO3--N为主,且淋失系数高于水田,提高有机肥替代比可以大幅降低旱地氮素淋失,但增强了DON淋失。因子重要性分析表明：有机肥替代比对TN淋失影响占主导作用,而施氮水平对NO3--N、DON淋失影响更为重要。因此,低施氮量、高替代比动物型有机肥可有效减少碱性旱地土壤氮素淋失,为有机肥配施化肥的农田应用提供依据。     

我国新型肥料产业发展战略研究

肥料产业服务于农业生产,尿素、磷铵、氯化钾和复合肥等传统化肥产品的大量投入对保障粮食安全发挥了至关重要的作用。随着我国农业发展方式从资源消耗型向绿色可持续型转变,发展新型高效肥料产业,提升肥料产品对粮食安全与生态环境安全的协同保障作用,是现阶段国家农业绿色发展的一个关键举措。新型肥料类型主要有缓/控释肥料、增值肥料、水溶肥料、商品有机肥、微生物肥料等,相比于常规施肥,施用新型肥料普遍能够提高作物产量和养分利用效率,增产率范围为4.6%～17.5%,氮肥利用率提高16.8%～52.3%,农田土壤氨挥发损失量可降低7.2%～50.7%,N₂O排放降低8.1%～40.8%,氮淋溶损失降低16.5%～43.8%,氮径流损失降低22.1%～45.4%。经过几十年的跟踪和创新,我国新型肥料形成了产业化,新型肥料总产量已位居世界前列。但由于新型肥料产业起步晚,几乎所有类型的新型肥料生产均存在原创核心技术缺乏,产品特性与农业需求匹配性不高,施肥技术和装备发展滞后,以及监管体系薄弱等问题。为推动新阶段新型肥料产业结构绿色高效转型升级,未来我国的新型肥料产业发展战略核心包括以下4个方面:1) 以农业需求为导向,提升肥料产品与生产需求的匹配度;2) 肥料增效技术由注重养分供给向土壤环境、作物吸收和有效供给综合调控发展,肥料增效材料向高效、环保和价廉方向发展,肥料产品向营养、土壤改良和抗逆等多功能发展;3) 注重最大限度地利用资源,降低能耗,通过大型肥料生产设备的优化和改造,力争实现新型肥料由二次加工到一次生产的突破,实现新型肥料生产的绿色低碳转型;4) 建立健全肥料生产、销售和使用全链条监管体系,保障新型肥料产业的高质量健康发展。     

肥料混施对赤红壤氮磷淋失特征的影响

采用室内模拟土柱淋洗方法研究了无机复合肥、有机复合肥、猪粪堆肥和花生麸4种肥料单施和两两混施条件下氮磷在赤红壤中的淋失特征。结果表明,各处理总氮淋失率在43.2%～74.8%之间,总磷淋失率在0.01%～0.08%之间,赤红壤中肥料氮淋失严重,肥料磷淋失有限。肥料单施处理的无机氮淋失量和有机氮基本相近,肥料混施处理的无机氮淋失量远高于有机氮;各施肥处理磷的淋失均以颗粒磷为主。肥料混施显著增加铵态氮和无机氮淋失,减少有机氮和总氮淋失。猪粪与复合肥混施减少颗粒磷和总磷淋失,花生麸与复合肥混施则促进颗粒磷和总磷淋失,所有混施处理均减少可溶性磷淋失。肥料混施对赤红壤氮磷淋失特征具有显著的混施效应。     

Plant availability and leaching of 15N-labelled mineral fertilizer residues retained in agricultural soil for 25 years: A lysimeter study

Background

A high use-efficiency of fertilizer N remains essential to sustain high crop productivity with low environmental impact. However, little is known on the long-term lability of mineral fertilizer N.

Aims

To quantify crop uptake and leaching of ¹⁵N-labelled mineral fertilizer that has been retained in an agricultural soil for 25–30 years in crops with variable growing season.

Methods

A field plot received ¹⁵N-labelled mineral fertilizers over a period of 5 years and was then kept under arable cropping for 12 years. After relocation to 16 lysimeters, the topsoil grew set-aside grassland for the next 13 years. Then crop uptakes and leaching losses of ¹⁵N remaining in soil was tested over a 2-year period by either converting set-aside grass to production grassland, or by replacing it with spring barley (+/− autumn cover crop) or vegetation-free fallow. All treatments received unlabelled mineral N fertilizers.

Results

Crop uptake and leaching of ¹⁵N were generally highest in the first test year after termination of the set-aside. The leaching of residual ¹⁵N in soil declined in the order: vegetation-free soil (4.7%), spring barley (1.9%), spring barley + cover crop (0.7%) and production grassland (0.2%). Corresponding losses for the second leaching period were 2.7%, 0.9%, 0.4% and 0.06%. There was a fixed relationship between leaching losses of ¹⁵N and total N.

Conclusions

After residing in soil for 25–30 years, the lability of labelled mineral N fertilizer residues appeared slightly higher than the lability of bulk soil N. Autumn vegetation was crucial for reducing leaching losses.     

Nutrient management on crop productivity and changes in soil organic carbon and fertility in a four–year-old maize-wheat cropping system in Indo-Gangetic plains of India

The aim of this investigation was to prepare and evaluate organic manures (vermicompost, compost and FYM) and mineral fertilizers on crop productivity and changes in soil organic carbon (SOC) and fertility under a four-year-old maize-wheat cropping system. The results demonstrated that yields and nutrient uptake by crops increased significantly in plots receiving manures and mineral fertilizers either alone or in combination than unfertilized control. Application of manures and fertilizers also enhanced SOC, mineral N, Olsen-P and ammonium acetate-extractable K (NH₄OAc-K) after both the crops. Surface soil maintained greater build-up in SOC, mineral N, Olsen-P and NH₄OAc-K than sub-surface soil. Plots amended with manures at 5 t ha^?1 and 50% recommended dose of fertilizer (RDF) had pronounced impact on improving SOC and fertility after both the crops indicating that integrated use of manures and mineral fertilizers could be followed to improve and maintain soil fertility, increase crop productivity under intensive cropping system.     

农田径流氮磷污染负荷的田间施肥控制效应

由施肥不当造成的农田N、P污染物径流输出是农业非点源污染的主要问题。采用模拟实验的方法，研究了不同施肥方法、不同肥料配方对土壤地表径流N、P流失的影响。结果表明，合理而有效的施肥方法可以作为农田地表径流N、P污染的田间控制技术。合理的基肥比例及追肥次数，适当的种植密度及适量的N肥、P肥，既可提高白菜产量，同时又降低径流中N、P的流失量；不同改性肥料配方可以调控农田径流N、P的污染负荷。