不同施肥量和方式对小麦产量及土壤硝态氮的影响

通过大田试验研究了不同氮素水平下有机无机肥料配施对小麦产量和土壤硝态氮累积量的影响.结果表明,小麦产量随着氮素水平的提高而增加,同一施氮水平下,有机无机肥料配施方式下小麦的产量均显著高于单施有机肥或者单施无机肥.土壤中的硝态氮累积量随施氮量增加而升高,同一施氮水平下不同配施方式之间土体中的硝态氮累积量随着配施方式中无机氮肥所占比例的增加而升高.综合考虑冬小麦产量和土壤硝态氮累积量两个因素,纯氮施入量200 kg/hm2,75%的氮由有机肥提供、25%的氮由尿素提供的处理为较理想的氮素施用水平和配比组合.     

苏北滩涂区施肥对菊芋生长和土壤氮素累积的影响

通过在苏北滩涂区开展的田间试验,分析了不同施肥量对菊芋地下、地上干物质累积,及对土壤铵态氮、硝态氮的累积及其动态变化过程的影响。结果表明,氮素是苏北沿海滩涂菊芋生长的关键限制因子,增施氮肥可以显著提高菊芋地下和地上干物质的积累。在氮肥供应充足情况下,适当增施磷肥(75kg·hm-2)可以增加菊芋地下和地上干物质的积累。施氮量小于150kg·hm-2时,土壤中氮素处于净消耗状态,施氮量225kg·hm-2时,不仅可以获得菊芋地下和地上干物质的最大产量,且有助于土壤氮素的累积。硝态氮是苏北沿海滩土壤氮素淋失的主要形态,且降水是导致硝态氮淋失的重要原因。随施氮量增加,土壤氮素淋失的风险加大。     

不同氮素管理方法下棉花产量和氮肥利用率

在滴灌条件下,研究农民习惯施氮模式、过量施氮模式、基于无机氮储量(Nmin)的氮素管理模式、基于计算机视觉的氮素营养诊断和氮素推荐施肥技术对棉花产量、氮肥利用率的影响。结果表明,基于计算机视觉的氮素营养诊断施肥技术和基于土壤Nmin的氮素管理模式比常规施肥模式分别减少了氮肥施肥量37.8%和56.3%,同时获得与常规施肥量相同的产量;与农民习惯施氮量相比,基于Nmin的氮素管理模式提高氮肥利用率27.80%,基于计算机视觉的氮素管理方法提高氮肥利用率16.96%;基于Nmin的氮素管理方法硝态氮残留为负值,基于计算机视觉的氮素管理方法比农民习惯施氮量减少了土壤硝态氮残留89.02%。基于Nmin或基于计算机视觉的氮素管理方法可明显提高氮肥施肥推荐质量,减少氮肥浪费,并减少对环境的氮排放。     

不同施氮水平对春玉米氮素利用及土壤硝态氮残留的影响

过量施用氮肥造成的环境问题日益严重,氮肥合理使用成为了人们研究的热点.通过研究不同施氮水平对春玉米氮索利用及土壤硝态氮残留的影响,为氮肥的合理利用提供依据.通过在北京市通州区农业技术推广站进行田间小区试验,研究了不同施氮量(0、50、100、200和300kg·hm~(-2))对春玉米产量及氮素利用效率、氮平衡和土壤硝态氮累积量的影响.结果表明:(1)春玉米在施氮量为200kg·hm~(-2)时达到最高产量,为9 006.4 kg·hm~(-2),不同氮肥水平的氮肥利用率在19.7%～25.8%之间,在100 kg·hm~(-2)时的利用效率最高,达到25.8%.(2)作物吸氮量随输入量的增加而增加,氮盈余主要以土壤残留为主,表观损失在氮盈余中的比例虽小,但随施氮量的增加而增加的趋势更加明显.(3)硝态氮在180cm土层中的累积量随氮素输入量的增加而显著增加,在300 kg·hm‘2时达到最高值,为195 kg·hm~(-2),在施氮水平为100 kg·hm~(-2)时作物生长的需要就基本上能够得到满足,而在高施氮水平下(200和300 kg·hm~(-2))时土壤中的硝态氮出现富集现象,对环境形成一定的威胁.     

不同水氮处理对棉田氮素平衡及土壤硝态氮移动的影响

 【目的】探讨不同水氮管理策略对高产棉田氮素平衡及氮素移动的影响。【方法】设置田间小区试验,研究了常规灌水＋常规施氮、优化灌水＋优化施氮、常规灌水＋优化施氮、优化灌水＋优化施氮、常规灌水+不施氮处理条件下的棉田氮素平衡和土壤硝态氮动态。【结果】在常规水氮管理条件下,收获后表观损失量高达163—294 kg?hm-2,60—200 cm土层中硝态氮含量较播前有大幅增加,增量与表观损失的比值达到0.39—0.69;优化水氮管理条件下表观损失量仅为19—87 kg?hm-2;常规水氮处理不同层次土壤剖面上均呈现出硝态氮的积累,而且随灌水量加大累积峰下移,优化水氮管理土壤剖面硝态氮累积程度较小。【结论】在常规施氮体系中氮素的表观损失率达52%—68％,氮素随水移动到根层以下是重要的损失途径之一;本试验中采用的优化水氮管理方法显著减少了硝态氮的淋移损失。     

东北春玉米连作体系土壤剖面无机氮的变化特征

【目的】研究不同施肥方式对东北春玉米生长及连作体系土壤中氮素含量的影响,为春玉米的合理施肥提供理论依据。【方法】2005-2006年,在东北中部黑土春玉米连作区进行2年的田间定点试验,研究了一次性施肥（农民习惯施肥1、农民习惯施肥2）和推荐施肥条件下,玉米不同生育阶段地上部生物量和吸氮量及土壤无机氮含量的变化特征,并对土壤氮素表观盈亏进行了估算。【结果】玉米地上部生物量和吸氮量均随施氮量的增加而增大,其中推荐施肥处理的生物量和吸氮量均最高。施氮显著增加了0～90 cm土层中的无机氮含量。2个习惯施肥处理土壤的硝态氮含量受降雨量的影响较大,且下移明显;推荐施肥处理可明显降低硝态氮在土壤中的残留。土壤氮素表观盈亏取决于氮肥用量,2006年农民习惯施肥1处理的土壤氮素表观盈余量最高,且多以残留硝态氮的形式累积在深层土壤中。【结论】在东北黑土春玉米连作区,氮肥一次性基施会导致土壤中的无机氮高残留,增加氮损失,易对该地区的生态环境造成威胁,本试验中的推荐施肥是较好的施肥方式。     

施用肥料添加剂对太湖地区水稻产量、氮素吸收利用及氮平衡的影响

通过田间试验研究三个供氮水平下(施氮50 kg/hm2、150 kg/hm2、250 kg/hm2)施用肥料添加剂对苏南太湖地区水稻产量、氮素吸收利用及土壤氮平衡的影响。结果表明,施氮和肥料添加剂对水稻产量、氮肥吸收利用及表观损失氮均有显著影响,但只有在水稻产量和氮肥农学利用率指标上二者表现出显著的交互作用(P0.05);随施氮量增加,水稻产量、累积吸氮量、土壤残留无机氮(Nmin)、表观损失氮增加,氮肥吸收利用率和农学利用率降低;与单施尿素相比,尿素配施肥料添加剂可进一步增加水稻产量、累积吸氮量,并能提升氮肥利用率和降低表观损失氮量,且该效应总体上随施氮量增加而愈趋明显;施用肥料添加剂对水稻营养生长期的氮素积累影响要明显强于生殖生长期。在本研究条件下,综合分析水稻产量、氮肥利用及氮平衡指标,不施用肥料添加剂时,施氮150 kg/hm2可获得较好的农学和环境效应。     

不同氮肥用量对设施番茄产量、品质和土壤硝态氮累积的影响

在设施栽培条件下,采用田间小区试验,以番茄为指示植物,研究了不同氮肥用量:农民习惯施氮量(N1,尿素,纯氮1 000kg·hm-2)、70%农民习惯施氮量(N2、尿素,纯氮700 kg·hm-2)、70%农民习惯施氮量结合调节土壤C/N(N3,尿素,纯氮700 kg·hm-2)、50%农民习惯施氮量结合调节土壤C/N和采用滴灌(N4,尿素,纯氮500 kg·hm-2)对设施番茄产量、品质和土壤硝态氮累积的影响.结果表明,与农民习惯施用氮肥相比,减施氮肥处理(N2、N3和N4)的番茄产量没有降低.N4处理产量最高,比N1增产9.7%.N2和N4处理氮肥的农学效率和肥料的产投比均显著高于N1处理(P＜0.05),其中N4处理最高,为28.9 kg·kg-1和12.6,施肥效益最高.不同施氮肥处理间果实Vc含量虽没有显著差异,但N4处理是N1处理的1.2倍.番笳果实的硝酸盐含量随氮肥施用量的增加而增加,两者旱显著的正相关关系(R2=0.8307,P＜0.05),N3和N4处理果实硝酸盐含量均显著低于Nl处理(P＜0.05).0～100 cm土层累积的硝态氮随氮肥施用量的增加而增加,N1处理土层累积的硝态氮含量最高,减施氮肥处理均降低了土壤对硝态氮的累积.土壤硝态氮多累积在0～40 cm土层,硝态氮的相对累积量约为50%,这部分残留的氮素可被下季作物吸收利用.果实硝酸盐含量与土壤累积的硝态氮存在显著的相关关系(R2=0.800 3,P＜0.05),说明土壤硝态氮含量过高能够增加果实对氮素的吸收和积累.在寿光设施蔬菜生产条件下,在农民习惯施氮量基础上减氮30%～50%既町以保证较高产量和较好的果实品质,同时降低土壤中硝态氮累积.从产量、肥料效益和土壤可持续利用角度来看,N4处理更具优势,具有较好应用价值.     

不同肥料用量及配比对设施土壤硝态氮含量的影响

通过大田实验研究不同氮磷钾肥用量、氮磷钾配施、有机无机肥配施对设施土壤硝态氮残留的影响.结果表明:设施土壤中硝态氮质量比随着氮肥用量的增加迅速增加,并且随着种植年限增加不断累加;而适量的磷肥和钾肥有利于降低硝态氮的质量比.与不施肥处理相比,单施有机肥时土壤中残留的硝态氮较少,而单施化肥土壤中的硝态氮残留量明显增加,掺沙后促进了土壤有机氮和有机肥的矿化,使硝态氮累积量进一步增加.化肥与有机肥配施时,土壤的硝态氮质量比因作物而异,可能由于作物的生育期和需肥量不同导致的.     

广西赤红壤区玉米氮肥效应及适宜施氮量研究

【目的】确定广西赤红壤区玉米种植体系的农田适宜氮肥施用量,为该地区玉米产业的高产高效发展及农业生态环境的保护提供理论参考。【方法】通过春-秋连续2季播种种植玉米进行田间试验,研究不同施氮量(0、180、240、300、360和480 kg/hm~2)对玉米产量、氮肥利用率、0～100 cm土层土壤无机氮残留及氮素平衡的影响。【结果】①随着氮肥用量的增加,春、秋玉米产量均呈现先增加后降低的趋势,而氮肥当季利用率则呈现显著降低趋势。②施用氮肥增加了土壤硝态氮和铵态氮残留,以硝态氮为主,且硝态氮主要残留在0～40 cm土层,铵态氮主要分布在0～20 cm土层。③施用氮肥可显著影响0～100 cm土层土壤的无机氮积累量,施氮量高于360 kg/hm~2时,土壤的无机氮积累量增加显著。土壤氮素盈余量随施氮量增加而显著增加,春玉米生长季氮肥盈余部分绝大多数在土壤中残留,到秋玉米季继续施用高量氮肥,则同时显著增加土壤氮素残留和表观损失,且氮素表观损失量增幅更大。④土壤无机氮残留量与施氮量呈显著的指数增加关系,氮肥当季利用率与施氮量呈幂函数降低关系,春玉米生长季产量、土壤无机氮残留量分别与氮肥利用率交于200和322 kg/hm~2处,秋玉米生长季产量、土壤无机氮残留量分别与氮肥利用率交于211和300 kg/hm~2处。【结论】综合考虑本试验条件下玉米春秋连作体系中的氮肥残留后效作用,兼顾作物产量、环境效应与肥料效应,广西赤红壤玉米种植区的适宜氮肥季用量为N 200～300 kg/hm~2。     

Increasing soil microbial biomass nitrogen in crop rotation systems by improving nitrogen resources under nitrogen application

Soil microbial biomass nitrogen (MBN) contains the largest proportion of biologically active nitrogen (N) in soil, and is considered as a crucial participant in soil N cycling. Agronomic management practices such as crop rotation and mono-cropping systems, dramatically affect MBN in agroecosystems. However, the influence of crop rotation and mono-cropping in agroecosystems on MBN remains unclear. A meta-analysis based on 203 published studies was conducted to quantify the effect of crop rotation and mono-cropping systems on MBN under synthetic N fertilizer application. The analysis showed that crop rotation significantly stimulated the response ratio (RR) of MBN to N fertilization and this parameter reached the highest levels in upland-fallow rotations. Upland mono-cropping did not change the RR of MBN to N application, however, the RR of MBN to N application in paddy mono-cropping increased. The difference between crop rotation and mono-cropping systems appeared to be due to the various cropping management scenarios, and the pattern, rate and duration of N addition. Crop rotation systems led to a more positive effect on soil total N (TN) and a smaller reduction in soil pH than mono-cropping systems. The RR of MBN to N application was positively correlated with the RR of mineral N only in crop rotation systems and with the RR of soil pH only in mono-cropping systems. Combining the results of Random Forest (RF) model and structural equation model showed that the predominant driving factors of MBN changes in crop rotation systems were soil mineral N and TN, while in mono-cropping systems the main driving factor was soil pH. Overall, our study indicates that crop rotation can be an effective way to enhance MBN by improving soil N resources, which promote the resistance of MBN to low pH induced by intensive synthetic N fertilizer application.     

氮循环与中国农业氮管理

作为全球活性氮制造量和氮肥消费量均最大的国家,中国农业生态系统的氮平衡问题受到了国内外广泛的关注。普遍认为中国农田施氮过量问题突出,并产生了严重的环境污染。为全面了解中国农业生态系统的来源和去向,找出引起氮肥消费量高的原因,本研究运用氮循环基本原理,以2010年为例,根据近年来发表的文献和国家统计资料,详细讨论了不同空间尺度上中国农业生态系统的氮输出和输入,重点分析了作物-土壤系统氮循环与氮平衡的特征。2010年中国农业生态系统氮投入总体上过量,其数量基本上相当于经生物地球化学循环返回作物–土壤系统的氮量,大致在5 Tg N左右。在全国水平上,2010年化肥和有机肥带入农田的氮量,相等于作物吸氮量和农田氮损失量之和;由于化学氮肥流向的多样化,如林、牧、渔业和城市绿化等的氮肥消耗,以及部分经济作物包括果树和蔬菜,特别是设施蔬菜的高量施氮,总体上粮食作物过量施氮的问题并不十分突出。在耕地资源有限（占全球8%的耕地面积,养活20%的世界人口）、有机废弃物中氮养分循环利用率低于30%、豆科作物播种面积较少且生物固氮占农田总氮投入不足15%的情况下,中国的农业生产只有依靠氮肥。然而,中国氮肥消费存在着很大的地区差异,在土地生产力水平较高的黄淮海、长江中下游和珠江三角洲地区,单位农作物播种面积的施氮量显著高于全国平均水平。这些地区氮肥消费量较大与粮食单产高、复种指数高和豆科作物种植比例低有密切关系。因此,为保证人们不断增长的食物需求和膳食结构的改善,加之土壤基础肥力相对较低,农田化学氮肥投入较高具有一定的合理性。然而,农业生产过程中发生的氮损失,既浪费了资源,也污染了环境。损失进入大气和水中活性氮以及环境中新产生的活性氮,经生物地球化学循环过程以大气沉降和灌溉水返回农田,已经成为作物-土壤系统氮的重要投入项。由于农业生态系统中氮素转化过程的多样性和生物地球化学循环的复杂性,循环过程中的氮损失不可避免。只有通过在不同空间尺度上对氮素进行优化管理,才能将氮损失降低到最低。在保证粮食安全的基础上,尽可能地降低农田施氮的环境风险,需要多学科、多部门的协作与共同努力,在不同空间尺度上实现氮优化管理、达到降低农业生态系统氮肥投入的目的。     

Fate of Nitrogen from Organic and Inorganic Sources in Rice-Wheat Rotation Cropping System

The lower availability of N is one of the most important limiting factors impeding crop yield enhancement among the various factors that affect crop yield under the multiple-cropping agroecosystem in China.In this study,the recovery of a single application of 15N-labeled fertilizer or residues in rice-wheat cropping system was determined,in order to provide theoretical foundation for the nitrogen management in sustainable agricultural production.A continuous trace experiment was conducted for 15N microplots by using randomized block design with four treatments and four replications（T1 = 15N-labeled fertilizer with crop residue incorporation,T2 = 15N-labeled residues,T3 = 14N fertilizer to generate unlabeled crop residue,and T4 = 15Nlabeled fertilizer without crop residue incorporation）.Our results showed that,on average,17.17 and 12.01% of crop N was derived from N fertilizer and 15N-labeled residues,respectively during the first growing season,suggesting that approximately 82.83 or 87.99% of crop N was derived directly from soil N pool.There was a larger difference in the 15N recovery pattern in crop when N was applied as fertilizer or residues,i.e.,most of crop N derived from N fertilizer was absorbed in the first growing season（92.04%）,and the relevant value was 38.03% when 15N-labeled residues were applied.This implied that most of N fertilizer was recovered in the present cropping season,while a longer residue effect will be found for 15N-labeled residues.Thus,the average recovery of N fertilizer and N residue in the soil after the first growing season was 33.46 and 85.64%,respectively.The recovery of applied N in soil when N was applied as residues was significantly higher than that when N was applied as fertilizer.There was a larger difference in the total 15N recovery in plant and soil when N was applied as fertilizer or residues.By the end of the fifth or sixth cropping season,the total 15N recovery in plant and soil when N was applied as fertilizer or residues were estimated at 64.38 and 79.11%,respectively.On the contrary,there was little difference between the practices of residue incorporation and residue removal following the N fertilizer application.N fertilizer appeared to be more readily available to crops than residue-N,and residue-N replenished soil N pool,especially N in soil organic matter,much more than N fertilizer after six growing seasons.Therefore,residue-N is a better source for sustaining N content of soil organic matter.Thus,one possible management practice is to use both organic and inorganic N sources simultaneously to improve the use efficiency of N while protecting the sustainability of soil.     

SUSTAINABLE NITROGEN MANAGEMENT FOR VEGETABLE PRODUCTION IN CHINA

● Sustainable nitrogen management strategies for Chinese vegetable production are summarized. ● Research on reactive N (Nr) losses in Chinese vegetable systems is limited compared to cereal crop systems. ● Knowledge-based optimization of N fertilizer rate strategy maintains soil N supply to meet the dynamic vegetable demand in time, space and quantity. ● Innovative products and technology strategy regulates the soil N forms and promotes the vegetable root growth to further control the Nr loss. ● Integrated knowledge and products strategy is needed to produce more vegetables with lower Nr losses. Inappropriate nitrogen fertilizer management for the intensive Chinese vegetable production has caused low N use efficiency (NUE), high reactive nitrogen (Nr) losses and serious environmental risks with limited yield increase. Innovative N management strategy is an urgent need to achieve sustainable vegetable production. This paper summarizes recent studies on Nr losses and identifies the limitations from Chinese vegetable production systems and proposes three steps for sustainable N management in Chinese vegetable production. The three N management steps include, but are not limited to, (1) knowledge-based optimization of N fertilizer rate strategy, which maintains soil N supply to meet the dynamic vegetable demand in time, space and quantity; (2) innovative products and technology, which regulates the soil N forms and promotes the vegetable root growth to reduce the Nr loss; (3) integrated knowledge and products strategy (IKPS). The knowledge-based optimization of N fertilizer rate strategy and innovative products and technology, can maintain or increase vegetable yield, significantly improve NUE, and mitigate the region-specific and crop-specific Nr losses. More importantly, IKPS, based on combination of in-season root-zone N management strategy, innovative products and technology, and best crop cultivation management, is needed to produce more vegetables with lower Nr losses.     

氮肥施用下蚯蚓活动对农田氮转化影响的Meta分析

蚯蚓在自然土壤中既能促进植物氮(N)素利用、增加土壤N固持,也会导致土壤N素气逸和淋溶损失,但农田土壤中持续的N肥施用如何影响蚯蚓的这些作用却并不清楚。因此,本研究提取了52篇文献中的202对数据,利用Meta分析从N肥类型、施肥量和施肥方式3个方面进行研究,评估N肥施用下蚯蚓活动对农田N转化的影响。总体结果表明,N肥施用下蚯蚓活动显著增加了作物生物量(地上部、地下部分别增加了12.00%、19.30%)及作物总氮(TN)含量(地上部、地下部分别增加了20.35%、21.06%),显著增加了土壤可利用N(9.16%)、微生物生物量氮(MBN,23.19%)及脲酶活性(23.73%),但与此同时也导致土壤氧化亚氮(N₂O)排放和N淋溶增加了16.41%和16.15%。蚯蚓活动对不同肥料类型、施肥量及施肥方式下土壤N转化过程的影响不同。有机-无机N肥配施时,蚯蚓活动对作物生物量和TN含量均有显著的促进作用(地上部、地下部生物量分别增加了17.90%、18.03%;地上部、地下部TN含量分别增加了37.62%、25.76%);无论N肥施用量为多少,蚯蚓活动均显著增加了作...     

华北平原有机肥替代化肥条件下“粮-饲”轮作系统氮素表观平衡研究

为揭示有机肥替代化肥条件下华北平原不同轮作体系土壤-作物系统氮素表观平衡,布置田间试验,定量研究了不同施肥方式[化肥表施(C)、固态粪肥表施替代50%化肥氮(S)、液态粪肥注射施用替代50%化肥氮(L)]和不同轮作方式[籽粒玉米-小麦(T1)、青贮玉米/豇豆间作-填闲黑麦草(T2)、甜高粱-黑麦草(T3)、青贮玉米-黑麦草(T4)、高丹草-黑麦草(T5)]对作物地上部生物量及其氮携出量、0～200 cm土壤剖面硝态氮残留和土壤-作物系统氮表观损失的影响。结果表明:与轮作方式T1相比,T5夏秋季作物地上部生物量及其氮携出量提高幅度最大,其次为T3和T4,而T2却有所降低;各轮作方式冬春季地上部生物量较T1均有所降低,而对其氮携出量无明显影响。与施肥方式C相比,S和L可显著降低夏秋季作物地上部生物量及其氮携出量,降幅均小于15%,而对冬春季作物地上部生物量及其氮携出量无显著影响。与轮作方式T1相比,T3和T5可显著增加周年作物氮总输出量,且显著降低0～200 cm土层无机氮残留量和系统氮表观损失;与施肥方式C相比,S和L可显著降低周年作物氮总输出量和0～200 cm土层无机氮残留量,增加系统氮表观损失。研究表明,在华北平原农牧生产区,以养殖产生的固态和液态粪肥替代50%化肥氮条件下,甜高粱-黑麦草和高丹草-黑麦草轮作是氮肥偏生产力高、表观损失低的轮作方式。     

Tillage,crop residue,and nutrient management effects on soil organic carbon in rice-based cropping systems:A review

Soil organic carbon(SOC) sequestration is one of the major agricultural strategies to mitigate greenhouse gas(GHG)emissions,enhance food security,and improve agricultural sustainability.This paper synthesizes the much-needed stateof-knowledge on the effects of tillage,crop residue,and nutrient management practices on SOC sequestration and identifies potential research gap,opportunities,and challenges in studying SOC dynamics in rice(Oryza sativa L.)-based cropping systems in South Asia,mainly in Bangladesh,Bhutan,India,Nepal,Pakistan,and Sri Lanka.Improved management practices such as reduced- and no-tillage management,nitrogen(N) fertilizer and farmyard manure(FYM) application,and crop residue addition can improve SOC accumulation.Positive effects of no-tillage,crop residue addition,N addition through manure or compost application,and integration of organic and chemical fertilizers on SOC accumulation in rice-based cropping systems have been documented from South Asia.However,limited data and enormous discrepancies in SOC measurements across the region exist as the greatest challenge in increasing SOC sequestration and improving agricultural sustainability.More research on SOC as influenced by alternative tillage,crop residue,and nutrient management systems,and development of SOC monitoring system for existing long-term experiments will advance our understanding of the SOC dynamics in rice-based cropping systems and improve agricultural system sustainability in South Asia.     

Impacts of Fertilization Alternatives and Crop Straw Incorporation on N2O Emissions from a Spring Maize Field in Northeastern China

Spring maize is one of the most popular crops planted in northeastem China. The cropping systems involving spring maize have been maintaining high production through intensive management practices. However, the high rates of nitrogen （N） fertilizers application could have introduced a great amount of nitrous oxide （N2O） into the atmosphere. It is crucial for sustaining the maize production systems to reduce N2O emissions meanwhile maintaining the optimum yields by adopting alternative farming management practices. The goal of this study was to evaluate effects of alternative fertilization and crop residue management practices on N2O emission as well as crop yield for a typical maize field in northeastern China. Field experiments were conducted during the 2010-2011 maize growing seasons （from early May to late September） in Liaoning Province, northeastern China. N2O fluxes were measured at the field plots with six different treatments including no N fertilizer use （CK）, farmers＇ conventional N fertilizer application rate （FP）, reduced N fertilizer rate （OPT）, reduced N fertilizer rate combined with crop straw amendment （OPTS）, slow-release N fertilizer （CRF）, and reduced N fertilizer rate combined with nitrification inhibitor （OPT＋DCD）. The static chamber method combined with gas chromatography technique was employed to conduct the measurements of N2O fluxes. The field data showed that N2O emissions varied across the treatments. During the maize growing season in 2010, the total N2O emissions under the treatments of CK, FP, OPT, OPTS, and CRF were 0.63, 1.11, 1.03, 1.26, and 0.98 kg N ha-1, respectively. The seasonal cumulative N2O emissions were 0.54, 1.07, 0.96, 1.12, and 0.84 kg N ha1, respectively, under CK, FP, OPT, OPTS, and OPT＋DCD in 2011. In comparison with FP, CRF or OPT＋DCD reduced the N2O emissions by 12 or 21%, respectively, while the crop yields remained unchanged. The results indicate that the reduction of N-fertilizer application rate in combination with the slow-release fertilizer type or nitrification inhibitor could effectively mitigate N2O emissions from the tested field. The incorporation of crop residue didn＇t show positive effect on mitigating N2O emissions from the tested cropping system. The field study can provide useful information for the on-going debate on alternative N fertilization strategies and crop straw management in China. However, further studies would be needed to explore the long-term impacts of the alternative management practices on a wide range of environmental services.     

A NEW APPROACH TO HOLISTIC NITROGEN MANAGEMENT IN CHINA

● Progress on nitrogen management in agriculture is overviewed in China. ● 4R principles are key to high N use efficiency and low N losses in soil-crop systems. ● A new framework of food-chain-N-management is proposed. ● China’s success in N management provides models for other countries. Since the 1980s, the widespread use of N fertilizer has not only resulted in a strong increase in agricultural productivity but also caused a number of environmental problems, induced by excess reactive N emissions. A range of approaches to improve N management for increased agricultural production together with reduced environmental impacts has been proposed. The 4R principles (right product, right amount, right time and right place) for N fertilizer application have been essential for improving crop productivity and N use efficiency while reducing N losses. For example, site-specific N management (as part of 4R practice) reduced N fertilizer use by 32% and increased yield by 5% in China. However, it has not been enough to overcome the challenge of producing more food with reduced impact on the environment and health. This paper proposes a new framework of food-chain-nitrogen-management (FCNM). This involves good N management including the recycling of organic manures, optimized crop and animal production and improved human diets, with the aim of maximizing resource use efficiency and minimizing environmental emissions. FCNM could meet future challenges for food demand, resource sustainability and environmental safety, key issues for green agricultural transformation in China and other countries.     

EFFECTS OF SUBSTITUTION OF MINERAL NITROGEN WITH ORGANIC AMENDMENTS ON NITROGEN LOSS FROM SLOPING CROPLAND OF PURPLE SOIL

● Interflow acts as the dominant pathway for N loss loadings. ● The purple soil region is a hot spot of nitrate leaching in China. ● Mineral N substitution with organic amendments can be recommended as optimal practices for cropland N management. Nitrogen loss from purple soil can lead to large negative impacts to the environment considering the wide distribution of this soil type in the upper reaches of the Yangtze River. Therefore, nitrogen loss patterns from sloping cropland of purple soil in the Sichuan Basin with the following fertilization regimes were studied in a wheat-maize rotation system: 100% organic fertilizer (OM), using pig manure to replace 30% of mineral N (OMNPK) and crop residue to replace 15% of the mineral N (CRNPK) plus standard mineral fertilization (NPK) and no fertilizer control. The cumulative hydrological N loss could be as high as 45 kg·ha⁻¹ N. The interflow accounted for up to 90% of the total N loss followed by sediment and overland flow losses. The high N loss via interflow found in this study highlighting that sloping cropland of purple soil may be one of the hot spots of N leaching. Compared to the NPK regime, organic substitution regimes (i.e., OM, OMNPK and CRNPK) decreased total hydrological N loss loadings by 30% to 68%. In addition, they can maintain annual crop yields and decrease yield-scaled total hydrological N losses by 18% to 71%. In conclusion, long-term substitution of mineral N with organic amendments can maintain high crop productivity and reduce environmental N loss loadings, and thereby recommended as good N management practices to minimize the risk of agricultural non-point source pollution in the purple soil region of China.