Effects of Temperature and Nitrogen Input on Nitrogen Mineralization in Alpine Soils on Tibetan Plateau

[Objective] The study aimed to investigate the effects of temperature and nitrogen input on nitrogen mineralization in alpine soils on the Tibetan Plateau.[Method]An incubation experiment in the laboratory was conducted using three alpine soils.These soils were collected from the top 10 cm depth in three grassland types：alpine meadow in Haibei,alpine steppe in Naqu and alpine wetland in Dangxiong.[Result] Temperature significantly affected nitrogen mineralization in alpine soils of three grassland types.The mineralization rate in alpine steppe soil rose with the rise of temperature,while the mineralization rate in the alpine meadow soil and alpine wetland soil decreased with the rise of temperature.Nitrogen input had no significant effect on nitrogen mineralization in the alpine meadow soil,but significantly increased nitrogen mineralization in the alpine steppe soil and the alpine wetland soil.Grassland types significantly affected nitrogen mineralization in alpine grasslands.[Conclusion] The effects of temperature and nitrogen input on nitrogen mineralization in alpine soils on the Tibetan Plateau were significant.And those different effects depended on different types of grassland.

Spatio-temporal variation of net anthropogenic nitrogen inputs in the upper Yangtze River basin from 1990 to 2012

The net anthropogenic nitrogen input(NANI) is an important nutrient source that causes eutrophication in water bodies. Understanding the spatio-temporal variation of NANI is important for regional environment assessment and management.This paper calculated NANI in the upper Yangtze River basin(YRB), upstream of the Three Gorges Dam(TGD), from1990 to 2012, and analyzed its spatio-temporal characteristics. Over the past 23 years of the study, the average annual NANI increased from 3200 kg N km^(-2) to 4931 kg N km^(-2). The major components were fertilizer N application, atmospheric N deposition,and net food and feed N import. In the northwest high mountainous region with a sparse population, the main component was atmospheric N deposition. Fertilizer N application and net food and feed N import were concentrated in the Chengdu Plain because of the high population density and large areas of farmland. This research found that NANI increased with rapid urbanization and increasing population. The Pearson correlation results illustrated that the spatial distributions of NANI and its major components were affected by land cover/use, agricultural GDP and total population. Increasing NANI has been the major cause of the degrading stream water quality over the past 20 years and is becoming a major threat to the water quality of the TGD reservoir.

Discrimination between extraneous nitrogen input and interior nitrogen release in lakes

In this study the authors determined the nitrogen isotopes of nitrate and the carbon and nitrogen contents of water samples from the Hongfeng Lake and inflowing streams, and, on this basis, discriminated the extraneous nitrogen input and the interior nitrogen release (organic matter decomposition) in the lake. The results showed that the amount of extraneous nitrogen input into the Hongfeng Lake increases and the interior nitrogen release from the lake is intensified in winter and spring. Nitrogen mixing is relatively obvious at the catchments between the lake inlet and inflowing streams, while organic matter decomposition (nitrification) is most intense in the middle and lower reaches of the lake. In winter and spring the organic matter decomposition takes place mainly at the middle level of the water column in the middle and lower reaches of the lake, which has a bearing on the abundance of degraded organic matter at this water level. This part of degraded organic matter contains a considerable proportion of hydrogenous nitrogen in the lake.

Water and nitrogen input optimization for jujube trees under surge root irrigation based on weighted grey correlation model

In order to obtain the optimal input of water and nitrogen(W&N)suitable for the jujube trees in Northern Shaanxi,12 treatments had been set in the demonstration base of micro-irrigation jujube tree of Mizhi County in 2014-2015 through field experiment of jujube trees under surge root irrigation(SRI),in which three soil moisture levels(high moisture level W1:60%-85%θ,middle moisture level W2:50%-75%θ,low moisture level W3:40%-65%θ)and four nitrogen input levels(high nitrogen F75:0.75 kg/plant,middle nitrogen F50:0.50 kg/plant,low nitrogen F25:0.25 kg/plant,no nitrogen F0:0.00 kg/plant)were set.Through analyzing the effects of different W&N inputs on the yield,net income(NI)and W&N utilization efficiency(WUE and NUE)of jujube trees and establishing a weighted grey correlation model,the optimization of W&N input for jujube trees could be achieved under SRI.Results showed that different W&N inputs had significant influences on yield,NI,WUE and NUE.Along with the increase of soil moisture content,the yield and NUE increased,while WUE decreased gradually,and the NI had the tendency to increase first and then decrease.Along with the increase of nitrogen input,the yield,NI and WUE had the tendency to increase first and then decrease while the NUE decreased significantly,and the yield,NI,WUE and NUE could not reach the maximum at the same time.Through the study on the grey correlation model of jujube tree’s comprehensive benefit based on the yield,NI,WUE and NUE,results showed the comprehensive benefit of jujube trees was significantly different when W&N input was different,and the gray correlation degree of W2F25 treatment was the highest in two years,which means that the soil moisture content of 50%-75%θand nitrogen input of 0.25 kg/plant was the optimal W&N input for jujube trees under SRI in Northern Shaanxi area.

Estimating total nitrogen deposition in agroecosystems in northern China during the wheat cropping season

Atmospheric nitrogen (N) deposition has been poorly documented in northern China, an intensive agricultural and industrial region with large emissions of NHx and NOy. To quantify N deposition, total airborne N deposition was determined at three agricultural sites using a manual integrated total nitrogen input (ITNI) system during growth of winter wheat (Triticum aestivum L.) and Italian ryegrass (Lolium multiflorum Lam.) from September 2005 to May 2006. Total estimated N deposition averaged 54.9 and 43.2 kg N/hm2 across the three sites when wheat was grown to flowering and maturing, respectively. The average value was 50.2 kg N/hm2 when ryegrass was the indicator plant. Both indicator species gave similar total airborne N input results. The intermediate level of N supplied resulted in the highest N deposition, and the ratio of N acquired from deposition to total N content of the whole system decreased with increasing N supply to the roots. The contribution of atmospheric N to the total N content of the wheat and ryegrass sand culture systems ranged from 10% to 24%.

Potential Breeding for High Nitrogen Fixation in <i>Pisum sativum</i>L.: Germplasm Phenotypic Characterization and Genetic Investigation

Nitrogen (N) is the most yield-limiting crop nutrient worldwide. Industrially produced N has increased in cost over the past years, and is unavailable in many regions around the globe. Biological N fixation by rhizobial bacteria is a great underutilized resource that this project aims to maximize. Grain legumes fix approximately 20 to 100 kg·N·ha-1·yr-1. The amount of N supplied by fixation is affected by genes and traits of both the bacterial and plant partners. The objectives of this study are to identify Pisum sativum varieties with high nitrogen fixation efficiency. This is achieved by germplasm screening and phenotypic evaluation of nodule formation, total plant nitrogen, and residual nitrogen in soil. Significant differences in plant total nitrogen among the various cultivated genotypes were found, with heritability of 0.57. These pea varieties left in the soil a residual N that varies between 11.21 to 65.018 kg.N.ha-1. Our findings reveal a unique opportunity for improving N fixation through genetic crossing and selection.

湿地甲烷代谢对氮输入响应的复杂性及其机制分析

氮素是影响湿地甲烷代谢过程的重要因素之一。氮输入是否影响湿地甲烷排放,增加全球气候变暖的风险,一直受到科学界的高度关注。目前关于氮输入对湿地甲烷排放影响的几篇meta-analysis文章的主要结论均为氮输入促进湿地甲烷排放,但是多篇研究性论文的结果为氮输入抑制或不影响湿地甲烷排放,由此可见氮输入对湿地甲烷排放的影响十分复杂。湿地甲烷代谢包括湿地甲烷产生、氧化和传输过程以及最终的甲烷排放,综述不同形态氮输入对水稻田、内陆湿地和滨海湿地甲烷排放通量影响的复杂性;分析湿地甲烷产生速率和途径、甲烷好氧氧化和硝酸盐/亚硝酸盐型厌氧甲烷氧化对不同形态氮输入的响应及机制。硝态氮输入对湿地甲烷产生具有抑制作用已成共识,然而其它形态氮输入对湿地土壤甲烷产生的影响具有较大的不确定性,氮输入影响湿地甲烷产生的机制主要包括电子受体-底物竞争机制、离子毒性机制、促进植物生长-碳底物供给增加机制以及pH调控机制等。氮输入对湿地好氧甲烷氧化影响的研究多集中在水稻田和泥炭湿地,影响的结果包括促进、抑制或影响不显著;氮输入促进湿地土壤硝酸盐/亚硝酸盐型厌氧甲烷氧化。着重分析氮输入对湿地甲烷代谢影响不确定性的成因,指出湿地甲烷代谢对氮输入的响应是一个生态系统层面的生物地球化学过程,并提出氮输入是最具争议效应的驱动因素之一,其对甲烷代谢的影响很难得出明确的模式,可能需要考虑湿地土壤特征(本底氮含量、有机碳含量、土壤C:N值等)以及植物群落类型和特征,最后提出今后在氮输入对湿地甲烷代谢影响方面应加强的研究领域。

河北省小麦生产体系中化肥投入的氮排放和碳足迹分析

分析河北省小麦生产的变化特征,并利用生命周期评价法(LCA)对化肥投入所产生氮排放和碳足迹进行定量分析,以期助力农业减排,为小麦产业绿色发展提供决策依据.结果表明:2003—2021年河北省小麦总产量逐年递增,播种面积基本稳定在2.3×10^(6)hm^(2)左右,单产增产显著;2010年之前播种面积增加对总产的贡献大,2011年后单产提升对总产贡献大;18年间小麦生产中纯氮肥和复混肥施用最多,分别占总量的39.4%和58.4%;氮肥偏生产力在19.3~26.4 kg/kg之间,呈上升走向;对环境产生的活性氮排放主要以NH3挥发为主,占总量的63.5%;2004—2021年化肥投入对环境所产生的总碳排放量下降34.5%,单位面积化肥投入所产生的碳排放下降28.2%;化肥生产碳排放>化肥施用碳排放;对化肥投入碳足迹影响的主要因素是纯氮肥用量.

省际粮食贸易隐含污染与环境比较优势研究

为协调粮食生产、贸易与面源污染的矛盾,实现绿色农业发展、区域间利益共赢,在测算省际粮食贸易量的基础上,运用灰水足迹方法计算各省隐含氮污染和污染强度,构建了粮食贸易隐含氮污染网络,解析了省际粮食生产隐含氮污染的环境比较优势。结果表明:中国省际粮食贸易网络格局由“条块式”转向“团块式”,贸易集中化趋势明显;省际粮食贸易隐含污染和污染强度呈下降趋势,但地区差异明显加剧了环境不公平;环境比较优势网络表现出“两头小,中间大”的橄榄形分布,环境比较优势最小的地区集中在华北地区,最大为黑龙江。

稻麦复种模式下氮肥与稻秸互作对小麦产量和N_(2)O排放影响及推荐施肥研究

优化氮肥施用和秸秆还田技术为途径的农业管理措施被认为是提升农业可持续性的有效手段,然而当前关于氮肥和秸秆还田对小麦产量和N_(2)O排放影响的研究仍十分有限。为此,本研究基于2000—2022年发表的关于长江中下游流域氮肥和秸秆投入下小麦产量和N_(2)O排放变化的文献,运用随机森林建模,定量分析氮肥和秸秆还田对小麦产量和N_(2)O排放的影响,并结合情景设置进行了特定地点的小麦产量和N_(2)O排放模拟,同时评估了碳排放强度(CEE)和净生态系统经济效益(NEEB)。结果表明,建立的区域尺度小麦产量与N_(2)O排放对氮秸互作响应的随机森林模型,验证结果R^(2)分别为0.66和0.65,RMSE分别为0.70和1.11。结果表明施氮量和土壤有机质是影响小麦产量和N_(2)O排放的重要因素。综合来看,达到最大产量所需的氮肥量为208~212 kg hm^(-2),达到最小CEE所需的氮肥量为113~130 kg hm^(-2),达到最高的NEEB所需的氮肥量为202~205 kg hm^(-2),其中在6.75 t hm^(-2)的秸秆投入下施用202 kg hm^(-2)的氮肥可以获得最高的生态收益1.37万元。优化氮肥和秸秆投入具备减少作物碳排放强度并获得最大净生态环境效益的潜力。

氮磷添加对常绿阔叶林土壤团聚体有机碳及其与磷组分相关的影响

[目的]为探究磷输入如何调节大气氮沉降对土壤团聚体有机碳含量及碳与磷关系的影响。[方法]在常绿阔叶林土壤建立长达6年(2015-2021年)的养分添加长期监测试验平台,包括4个处理:对照[P0+N0,P0 kg/(hm^(2)·a)+N0 kg/(hm^(2)·a)]、氮添加[P0+N100,P0 kg/(hm^(2)·a)+N100 kg/(hm^(2)·a)]、磷输入[P50+N0,P50 kg/(hm^(2)·a)+N0 kg/(hm^(2)·a)]以及氮磷同时输入[P50+N100,P50 kg/(hm^(2)·a)+N100 kg/(hm^(2)·a)],各处理设3次重复,共计12个样地。于2021年8月采集样地0-10 cm土层土壤样品,测定基础理化性质、土壤粒径分布规律、不同粒径土壤团聚体磷组分及有机碳(SOC)含量。[结果](1)P0处理下,氮添加显著增加大团聚体占比,减少黏粒和粉粒含量,提高各团聚体粒径中SOC含量;氮添加分别显著降低和增加团聚体黏粒、粉粒中易分解态磷组分(LP)和难分解态磷组分(RP)含量。(2)P50处理下,氮添加显著提高土壤团聚体平均几何直径(GMD),对各粒径团聚体中磷组分和SOC含量均无显著影响。(3)P0处理下,土壤团聚体SOC与难分解态磷呈正相关关系;P50处理下,土壤团聚体SOC与各功能磷组分无显著相关。由此推断,P0处理下,氮添加通过提高常绿阔叶林土壤团聚体黏粒、粉粒径中难分解态磷而增加土壤有机碳的固持;P50处理下,氮添加对各粒径中有机碳的影响可能受到生物因素的调节,与磷的有效性无关。[结论]氮沉降对常绿阔叶林土壤团聚体中碳磷内在关系的影响受到磷的调控,研究结果为森林土壤碳循环应对全球气候变化提供数据支撑。

典型高原湖泊人类活动净氮磷输入时空变化及其影响因素——以云南星云湖为例

星云湖作为人类农业生产活动影响下环境问题突出的代表性高原湖泊,其水体健康与生态平衡对于区域可持续发展至关重要。因此,量化解析星云湖流域人类活动净氮磷输入时空来源变化及影响因素对于流域管理和湖泊恢复具有重要意义。基于社会经济统计数据,采用人类活动净氮输入(NANI)、人类活动净磷输入(NAPI)模型量化星云湖流域NANI、NAPI强度。结果表明,19892020年研究区NANI、NAPI均值分别为(14614±2196)和(3135±452)kg/(km^(2)·a),时间上呈现先上升后下降的变化趋势,且峰值出现在2015年,分别达到18076和3889 kg/(km^(2)·a);空间分布上,除东部NANI、NAPI较低外,其余区域均较高;化肥和食物/饲料输入分别是NANI和NAPI的最大来源,占比分别为58.2%~63.8%和30.5%~59.5%。此外,基于模型选择和变量重要性分析发现,经济作物产量和畜禽密度是影响NANI、NAPI变化的最主要因素。因此,星云湖流域氮磷管控应从调整种植结构和模式等控源措施入手,加快经济模式转型。本研究结果可为星云湖流域建立有效的氮磷综合管理措施提供科学依据。

互花米草入侵背景下氮输入增加对天津滨海湿地芦苇凋落物可培养细菌和真菌群落的影响

为了探究互花米草入侵和氮输入增加条件下滨海湿地微生物群落的变化,在天津滨海湿地选取3个样地(互花米草入侵程度不同)进行原位模拟增氮实验,分析不同实验条件下芦苇凋落物可培养细菌和真菌群落组成及多样性差异.结果显示:互花米草入侵提高了细菌和真菌的数量及多样性,且随着入侵程度的增加,微生物数量和多样性增加;随着氮输入水平的增加,细菌和真菌数量及多样性先增加后降低;土壤铵态氮含量和pH值是影响细菌群落组成的主导土壤因子,土壤有机质含量和铵态氮含量是影响真菌群落组成的主导土壤因子.

中国市域尺度人为净氮磷输入及其空间异质性分析

为解析中国人为净氮输入(NANI)和人为净磷输入(NAPI)的来源和空间分布,本研究构建了中国市域NANI和NAPI模型,核算了2020年中国367个市域单元NANI和NAPI,并采用标准差椭圆方程和莫兰指数对其进行空间异质性分析。主要结论为:①2020年中国NANI和NAPI分别为4596.43 kg N/(km^(2)·a)和840.02 kg P/(km^(2)·a);②化肥施用是NANI和NAPI的主要贡献源,其中80.93%、89.65%的市域单元分别为其最大贡献源;③中国NANI和NAPI空间分布具有明显的聚集性和异质性,以胡焕庸线为界,东南部地区的NANI和NAPI明显高于西北部,聚集区域主要分布在华北平原地区。NANI和NAPI模型是一种定量评估区域内氮磷排放状态的模型,能够为中国氮磷污染重点区域的识别、污染治理等提供技术支撑。

长期施肥处理对东北黑土真菌多样性和群落结构的影响

基于40年的长期氮磷定位试验,利用高通量测序的方法,对比分析了未施肥处理(CK)、氮肥处理(N)、磷肥处理(P)和氮磷处理(NP)下黑土土壤真菌群落的差异。结果表明,与CK处理相比,长期氮输入显著降低了土壤pH,显著提高土壤NO_(3)^(-)-N、NH_(4)^(+)-N和可溶性有机氮(DON)含量,而磷输入显著提高了土壤有效磷和总磷含量。土壤真菌类群门水平最丰富的为子囊菌门(相对丰度为63%~68%),毛霉门(相对丰度为15%~20%)和担子菌门(相对丰度为9%~15%)。不同施肥处理对真菌多样性产生了显著影响。NP处理土壤真菌扩增子序列变异数目和香农指数分别为405和4.16,显著低于CK,分别为502和4.64。基于非度量多维尺度分析发现NP和N处理真菌群落结构与CK和P处理显著分开。冗余分析发现土壤性质包括pH,NO_(3)^(-)-N和DON是影响土壤群落结构的主要影响因子。可见,长期氮磷施肥处理通过影响土壤性质而对土壤真菌群落产生了重要的影响。

石漠化山区露石岩面流对岩-土界面土壤氮磷淋溶与输入作用的研究

基岩出露的石漠化区露石岩面在承接降水(含穿透雨)后易形成岩面流,并携带岩面有机或无机物质输送至岩周土壤中,对岩-土界面土壤养分变化具有重要影响。为探明岩面流对岩-土界面土壤氮磷的淋溶与输入影响,选取基岩明显出露的休耕地(1年岩面流作用)、退耕灌草地(5年岩面流作用)和坡耕地(无/少岩面流作用)3种样地,并分别选择外凸、平直和内凹3种特殊的岩面形状,研究了距岩面不同水平距离及土层的岩-土界面及非岩-土界面土壤的全氮和全磷变化特征。结果表明:岩面流对0~10 cm表层岩-土界面土壤氮磷产生输入或淋溶作用,对10~20 cm层岩-土界面土壤氮磷作用不明显。不同岩面形状形成的岩面流对岩-土界面土壤氮磷的淋溶与输入作用强度依次为:内凹型>平直型>外凸型。其中,在1年岩面流作用的休耕地中,内凹型岩面形成的岩面流对岩-土界面土壤氮素的影响主要表现为淋溶,而平直型和外凸型岩面表现为输入作用;不同形状岩面流对岩-土界面土壤磷素的影响均表现为淋溶。然而,在植被生长较好的退耕灌草地中,5年岩面流作用下不同形状岩面流对岩-土界面土壤氮磷的影响主要表现为输入。研究结果可为深入认识出露岩石对喀斯特生态系统土壤特性的影响提供科学依据。

外源氮输入对黄河三角洲盐地碱蓬CHCl_(3)和CHBr_(3)通量特征的影响

氯仿(CHCl_(3))和溴仿(CHBr_(3))是两种重要的挥发性卤代烃(Volatile halohydrocarbon,VHCs),可通过光化学作用,引起臭氧层破坏和温室效应,影响全球气候变化。以黄河三角洲湿地的优势物种—盐地碱蓬(Suaeda glauca)为研究对象,采用室内盆栽培养来探究不同浓度氮输入水平(CK,对照,6.0 g N m^(-2) a^(-1);1.5N0,低氮处理,9.0 g N m^(-2) a^(-1);3.0N0,高氮处理,18.0 g N m^(-2) a^(-1))对盐地碱蓬以及盆栽微生态系统CHCl_(3)、CHBr_(3)通量特征的影响。结果表明,不同氮梯度下盐地碱蓬CHCl_(3)和CHBr_(3)排放通量均呈现出先降后升的趋势,低浓度1.5N0下可以促进盐地碱蓬CHCl_(3)的释放,高浓度3.0N0则抑制;盐地碱蓬CHCl_(3)、CHBr_(3)气体通量的峰值分别出现在枯萎期与苗期,其主要原因是不同氮梯度刺激了气体消耗与产生之间的平衡以及植物各生长期生长因子的改变。由相关性分析可知,盐地碱蓬CHCl_(3)排放通量受多种因子相互作用,植物根长与CHBr_(3)排放之间存在显著相关性,根部越长,CHBr_(3)的排放通量越低。不同氮梯度下盆栽微生态系统内CHCl_(3)、CHBr_(3)排放通量的变化趋势不同,CHCl_(3)通量为先升后降,CHBr_(3)为先降后升,气体通量的最高值与最低值出现在植物不同生长时期,盆栽微生态系统气体排放通量主要受土壤NH^(+)_(4)-N、NO^(-)_(3)-N、以及植物凋落物等交互作用的影响。

大热输入条件下氮含量对低碳Mo-V-Ti-B微合金钢粗晶热影响区组织与冲击韧性的影响

采用Gleeble研究了大热输入条件下,氮含量对低碳Mo-V-Ti-B微合金钢焊接粗晶热影响区组织和冲击韧性的影响。结果表明,在100 kJ/cm热输入条件下,85 N、110 N和144 N试验钢粗晶热影响区-20℃冲击功分别为186 J、97 J和57 J。随着试验钢中氮含量的增加,试验钢粗晶热影响区冲击功逐渐降低。当氮含量从85 ppm增加至110 ppm时,低碳Mo-V-Ti-B微合金钢焊接粗晶热影响区组织由块状铁素体+大量针状铁素体转变为块状铁素体+少量的针状铁素体,组织发生粗化,故粗晶热影响区冲击功降低。当氮含量从110 ppm进一步增加至144 ppm时,粗晶热影响区组织由块状铁素体+少量的针状铁素体转变为块状铁素体+珠光体,虽然块状铁素体晶粒发生细化,但是粗晶热影响区组织中的“硬相”珠光体的含量增加,并且珠光体尺寸较大,在冲击试样变形过程中“硬相”珠光体与基体形变不协调,从而导致裂纹的萌生,造成冲击功进一步下降。

陕西果园主要分布区氮素投入特点及氮负荷风险分析

为了研究果园氮素投入特点及分析氮素负荷特征,加强果园氮素管理、指导果农科学合理施肥。以陕西省果园主要分布区土壤氮素分析、农户投入调查等统计数据为基础,采用盈余法从果树种类和区域角度分析果园生产体系中的氮素输入输出特点及氮素盈余状况。结果表明,陕西果园主要分布区平均化肥氮投入量927.2 kg/hm2,主要来源于尿素和复合肥,其中尿素占调查样本量的40%以上;通过有机肥投入的氮仅为139.4 kg/hm2。94.8%的果园氮素处于盈余,总体平均盈余量为876.3 kg/hm2,其中氮盈余量超过500 kg/hm2的样本占57.5%,盈余量超过1 000 kg/hm2的样本亦占了27.3%。不同果园相比,猕猴桃园氮素投入及盈余量最高,分别为1 432.9、1 186.9 kg/hm2。不同区域果园比较,土壤氮环境负荷以关中灌区果园较高,达1046.1kg/hm2。果园氮素施用与养分盈余量之间存在极显著的正相关。陕西果园氮素的高量投入给土壤环境带来较大的氮素负荷,这对土壤环境和周围水体造成很大威胁。

中国农田氮肥投入和生产效率

过去40年,中国氮肥用量增加、氮肥效率下降引起了国内外普遍关注,但中国不同作物氮肥用量及其利用效率缺乏大样本数据研究。本文通过农户调查及文献资料,对1970~2009年,尤其是从2000到2009年,中国主要农作物施氮量(化肥氮)、产量、氮效率(氮肥偏生产力)进行了研究。与2000~2003年相比,2008~2009年粮食、蔬菜、果树平均氮肥用量增加,单产增加,氮效率提高。粮食、蔬菜、果树氮肥用量分别增加26、36、107 kg/hm^2,产量分别增加1 280、5 722、18 802 kg/hm^2,氮效率分别增加2.2、6.6、25.2 kg/hm^2。东北、华北和长江中下游三大粮食作物主产区的氮效率都显著提高,而西北、西南和华南等地没有提高。与2000~2003年相比,2008~2009年中国平均氮效率的上升主要是因为单产大幅提高,而非氮肥用量下降。中国粮食作物单产较低,而氮肥用量高,未来在稳定氮肥投入的情况下继续提高单产是增效的主要途径。中国蔬菜和果树氮投入量太高,应该加强管理降低氮肥用量。