In the coming decades, a crucial challenge for humanity will be meeting future food demands without undermining further the integrity of the Earth's environmental systems(1-6). Agricultural systems are already major forces of global environmental degradation(4,7), but population growth and increasing consumption of calorie- and meat-intensive diets are expected to roughly double human food demand by 2050 (ref. 3). Responding to these pressures, there is increasing focus on 'sustainable intensification' as a means to increase yields on underperforming landscapes while simultaneously decreasing the environmental impacts of agricultural systems(2-4,8-11). However, it is unclear what such efforts might entail for the future of global agricultural landscapes. Here we present a global-scale assessment of intensification prospects from closing 'yield gaps' (differences between observed yields and those attainable in a given region), the spatial patterns of agricultural management practices and yield limitation, and the management changes that may be necessary to achieve increased yields. We find that global yield variability is heavily controlled by fertilizer use, irrigation and climate. Large production increases (45% to 70% for most crops) are possible from closing yield gaps to 100% of attainable yields, and the changes to management practices that are needed to close yield gaps vary considerably by region and current intensity. Furthermore, we find that there are large opportunities to reduce the environmental impact of agriculture by eliminating nutrient overuse, while still allowing an approximately 30% increase in production of major cereals (maize, wheat and rice). Meeting the food security and sustainability challenges of the coming decades is possible, but will require considerable changes in nutrient and water management.

China is experiencing intense air pollution caused in large part by anthropogenic emissions of reactive nitrogen(1,2). These emissions result in the deposition of atmospheric nitrogen (N) in terrestrial and aquatic ecosystems, with implications for human and ecosystem health, greenhouse gas balances and biological diversity(1,3-5). However, information on the magnitude and environmental impact of N deposition in China is limited. Here we use nationwide data sets on bulk N deposition, plant foliar N and crop N uptake (from long-term unfertilized soils) to evaluate N deposition dynamics and their effect on ecosystems across China between 1980 and 2010. We find that the average annual bulk deposition of N increased by approximately 8 kilograms of nitrogen per hectare (P < 0.001) between the 1980s (13.2 kilograms of nitrogen per hectare) and the 2000s (21.1 kilograms of nitrogen Per hectare). Nitrogen deposition rates in the industrialized and agriculturally intensified regions of China are as high as the peak levels of deposition in northwestern Europe in the 1980s(6), before the introduction of mitigation measures(7,8). Nitrogen from ammonium (NH4+) is the dominant form of N in bulk deposition, but the rate of increase is largest for deposition of N from nitrate (NO3-), in agreement with decreased ratios of NH3 to NOx emissions since 1980. We also find that the impact of N deposition on Chinese ecosystems includes significantly increased plant foliar N concentrations in natural and semi-natural (that is, non-agricultural) ecosystems and increased crop N uptake from long-term-unfertilized crop-lands. China and other economies are facing a continuing challenge to reduce emissions of reactive nitrogen, N deposition and their negative effects on human health and the environment.

【目的】本研究在定位试验平台上监测了不同施肥处理夏玉米田NH₃和N₂O的排放规律及其损失量,以探讨减少黄淮海区域夏玉米田氮素气态损失的有效途径,为提高夏玉米籽粒产量及肥料利用效率提供理论依据。【方法】2016—2017年利用水肥渗漏研究池进行试验,以郑单958（ZD958）为材料,以不施氮肥（CK）为对照处理,在同等施氮量下设置单施尿素（U₁）、单施牛粪（M₁）和尿素牛粪1﹕1配施（U₂M₂）3种氮肥处理。采用通气法和静态箱-气相色谱法研究了不同施肥处理对玉米田NH₃和N₂O排放规律和损失量、籽粒产量及氮肥利用效率的影响。【结果】玉米田氮素气态损失以NH₃挥发为主,占氮素气态损失量的88.55%—96.42%,N₂O排放量较少。不同施肥处理显著影响NH₃和N₂O排放量及氮素利用效率。U₁处理NH₃挥发量最高,两年平均为38.19 kg·hm^-2；以M₁处理最低,为19.10 kg·hm^-2,U₂M₂处理介于两者之间,施用有机肥的M₁或U₂M₂处理可以显著降低NH₃挥发损失量。N₂O排放氮素损失以M₁处理最高,平均达到1.65 kg·hm^-2,较U₁和U₂M₂处理分别提高了77.42%和34.15%。2016—2017年不同施肥处理间籽粒产量差异显著,表现为U₂M₂>U₁>M₁>CK,2016年U₂M₂处理籽粒产量较U₁和M₁处理分别提高了3.45%和5.25%,U₁和M₁处理之间籽粒产量无明显差异；2017年U₂M₂处理籽粒产量较U₁和M₁处理分别提高了5.83%和12.53%,U₁显著高于M₁处理,提高了6.33%。氮素利用效率以U₂M₂处理最高,平均为58.20%,较M₁和U₁处理分别提高了32.15%和15.13%。【结论】有机无机肥配施增加了干物质和氮素积累量,提高了夏玉米籽粒产量和氮素利用效率,较单施尿素氨挥发减少,较单施有机肥N₂O排放降低,是实现增产增效的合理施肥方式。

为提高基质肥料的缓释性能，该文选用10种有机和无机基质制备基质肥料，通过砂柱间歇淋洗的方法研究了基质肥料的氮素释放规律，并根据Logistic方程的参数和氮素释放拐点的UPGMA聚类分析评价了10种基质的缓释效果，结果表明：基质肥料氮素累积释放率随时间的动态变化可用一级动力学方程、Elovich方程、抛物线扩散方程和Logistic方程表征，其中以Logistic方程拟合效果最好，这说明定量描述氮素养分释放规律的方程中以Logistic方程评价更具有实效性，而有机基质中氧化淀粉和木质素的缓释效果较好，无机基质中膨润土的缓释效果最好。

Reducing the release rate of urea can increase its efficiency of use and reduce nitrogen pollution. A slow-release urea (S-urea) was produced using a new method; a bentonite and organic polymer (OP) were used to form a three-dimensional lattice structure by melting urea directly. The structure affected the recrystallisation of urea and increased its stacking density. The specific surface area of S-urea was 0.046 m(2) g(-1), much lower than that of common urea (1.698 m(2) g(-1) The static release experiment showed that 75% of 12 g sample of S-urea was released in 11 water for about 14 h, much longer than that of common urea (<0.5 h). The kinetic simulation results showed that the release of S-urea was not based on Fickian diffusion but underwent anomalous diffusion with its release rate was mainly affected by the dissolving-eroding process of the medium which was controlled by the compactness of the lattice structure. This process may be strengthened by increasing the amount of bentonite. (C) 2013 IAgrE. Published by Elsevier Ltd.

黄淮海地区是我国重要的小麦生产基地，在该地区使用新型高效控缓释对提高化肥利用效率，增加小麦单产具有重要作用。本试验在安徽、河南、山东和河北四省通过对等量和减量施用控失型复合肥和普通化肥的小麦产量比较，分析新型高效化肥对小麦的产量、产量构成、氮肥农学利用率的影响。结果表明，不施肥处理小麦产量360.30kg/667m2，施肥可以提高产量2-3成，是该区小麦增产的重要措施；在等养分施肥试验，控失型复合肥平均单产511.80 kg/667m2，较普通复合肥491.00 kg/667m2增产4.20%，氮肥农学利用率提高14.71%。从产量结构分析可以看出，控失型复合肥增产主要通过提高小麦亩穗数和成穗率来实现；减量试验显示，控失型复合肥较普通复合肥在平均氮肥减少28％的情况下，控失复合肥与普通复合肥平均单产分别是500.13kg/667m2和500.75 kg/667m2，产量几乎相平，其氮肥农学利用率提高36.59%。结果表明控失型复合肥是一种原理独特、高效的新型控缓释化肥。

Upland rice is an important crop in South America, including Brazil. Nitrogen (N) is one of the most yield-limiting nutrients in upland rice production in Brazil. A greenhouse experiment was conducted to evaluate N uptake and use efficiency as influenced by N sources. The soil used in the experiment was an Oxisol. The N sources were ammonium sulfate and urea, and N rates were 0, 50, 100, 150, 300, and 400 mg kg(-1) of soil. Nitrogen concentrations in the root, shoot, and grain were significantly influenced by N sources. The N rate and N source significantly influenced the N uptake in root, shoot, and grain. Similarly, nitrogen rate by N source interaction was also significant for N uptake in the root, shoot, and grain, indicating N source has a significant influence on uptake of N. Overall, concentration (content per unit dry weight) of N was greater in the grain, followed by root and shoot. Agronomical efficiency, apparent recovery efficiency, and utilization efficiency of N were significantly influenced by N rate and varied with N sources. However, physiological and agrophysiological efficiencies were only influenced significantly by N sources. Overall, N recovery efficiency was 33% for ammonium sulfate and 37% for urea. Hence, the large amount of N lost from soil-plant system may be by denitrification or voltilization.

Less than 50% of applied nitrogen (N) fertilizer is typically recovered by corn ( L.) due to climatic constraints, soil degradation, overapplication, and losses to air and water. Two application methods, two N sources, and two inhibitors were evaluated to reduce N losses and enhance crop uptake. The treatments included broadcast urea (BrUrea), BrUrea with a urease inhibitor (BrUrea+UI), BrUrea with a urease and a nitrification inhibitor (BrUrea+UI+NI), injection of urea ammonium nitrate (InjUAN), and injected with one or both inhibitors (InjUAN+UI, InjUAN+UI+NI), and a control. The BrUrea treatment lost 50% (64.4 kg N ha) of the applied N due to ammonia volatilization, but losses were reduced by 64% with BrUrea+UI+NI (23.0 kg N ha) and by 60% with InjUAN (26.1 kg N ha). Ammonia losses were lower and crop yields were greater in 2014 than 2013 as a result of the more favorable weather when N was applied in 2014. When ammonia volatilization was reduced by adding a urease inhibitor, NO emissions were increased by 30 to 31% with BrUrea+UI and InjUAN+UI compared with BrUrea and InjUAN, respectively. Pollution swapping was avoided when both inhibitors were used (BrUrea+UI+NI, InjUAN+UI+NI) as both ammonia volatilization and NO emissions were reduced, and corn grain yields increased by 5% with BrUrea+UI+NI and by 7% with InjUAN+UI+NI compared with BrUrea and InjUAN, respectively. The combination of two N management strategies (InjUAN+UI+NI) increased yields by 19% (12.9 t ha) compared with BrUrea (10.8 t ha).

大气中过量的氨会造成诸多环境问题并危害人类健康。我国农田氮肥施用后的氨挥发是一个重要的氨排放源。紫色土的土壤性质以及该区的气候条件导致其氨挥发潜力较大。与其他集约化农作区相比, 该区农田氨挥发研究相对较少。本文探讨了川中丘陵区紫色土冬小麦/夏玉米轮作体系氨挥发情况, 为开展陆地生态系统大气碳氮气体交换研究提供基础数据, 同时也为氨排放清单的编制及农田氨减排措施研究提供依据。选取川中紫色土丘陵区典型的坡耕地作为研究对象, 采用风洞法研究了紫色土冬小麦/夏玉米轮作体系的氨挥发动态过程。每次试验设置1个施肥处理, 3次重复。风速、风向、大气温湿度、土壤温湿度等气象数据由试验田微型气象站获取。每隔2~3 d采集土壤样品用以测定土壤NH₄⁺-N含量。两年的田间试验结果表明, 受氮肥深施及低温的影响, 冬小麦季氨挥发损失率明显低于夏玉米季; 2013年和2014年冬小麦季氨挥发损失率分别为7.4%和8.8%; 2013年夏玉米季三叶期氮肥撒施的氨挥发速率为34.1%; 2014年夏玉米季三叶期氮肥条施覆土降低了氨挥发损失, 损失率为21.4%; 2014年夏玉米季十叶期出现极端干旱的气候条件, 撒施氮肥后立即灌水使氨挥发损失率高达46.6%, 这是由于干旱条件下施肥灌水提供了利于氨挥发的土壤水分条件。因此在极端干旱的气候条件下, 应避免采用此施肥方式。综合分析两年的数据可得: 紫色土冬小麦季氨挥发损失占施氮量的(8.1±1.0)%, 夏玉米氨挥发损失占施氮量的(32.8±1.8)%。

【目的】 本文通过在陕西省长武县(CW)和吉林省梨树县(LS)的春玉米田间试验,研究了传统和优化施氮对春玉米产量、土壤氨挥发及氮平衡的影响,以探讨春玉米氮肥优化的潜力及其对农田氨减排的效果。【方法】 试验设对照、传统施氮(长武N 250 kg/hm², 梨树N 300 kg/hm²)及优化施氮(N 200 kg/hm²)3个处理,分别以N0、Ncon、Nopt表示。氨挥发采用德尔格氨管法(简称DTM法)进行原位测定,通过田间气象因素的校正计算氨挥发累积量。【结果】 长武和梨树点不同施氮处理下春玉米的产量结果表明,除对照(长武7.9 t/hm²、 梨树3.8 t/hm²)外,传统和优化施氮处理间均无显著差异(长武10.6～10.8 t/hm², 梨树9.5～9.6 t/hm²)。玉米氮肥利用率表现为优化施氮(44.3%～44.5%)显著高于传统施氮(33.6%～36.4%),其中长武点氮肥利用率提高了8.1个百分点,梨树点氮肥利用率增加了10.7个百分点。氨挥发田间监测结果显示,基肥翻耕入土后,伴随降雨的产生,长武和梨树点均未产生氨挥发。喇叭口追肥期表施氮肥后,长武和梨树点均产生大量氨挥发(占追施尿素氮量的16%～22%),减少追肥用量N 30 kg/hm²(长武点)和N 100 kg/hm²(梨树点)能显著减少氨挥发损失N 8和15 kg/hm²。土壤-春玉米系统氮平衡估算的结果显示,与长武点氮素表观矿化N 97 kg/hm²相比,梨树点仅为N 16 kg/hm²。优化施氮比传统施氮处理显著降低表观氮素盈余N 48～88 kg/hm²。长武点各施氮处理的表观氮素盈余中,约46%的氮素残留在0—1 m的土壤中,54%损失到环境中,氨挥发占总损失的15%～30%;梨树点表观氮素盈余中,35%损失到环境中,其中氨挥发占总损失的54%～75%,约有65%残留在0—1m的土壤中。梨树点传统施氮处理0—1 m土层的氮素残留达N 140 kg/hm²,部分残留在土壤中的氮素也将面临淋洗、硝化和反硝化等损失的风险。与优化施氮相比传统施氮氮素表观损失增加了约N 30～40 kg/hm²,除氨挥发损失外,淋洗和硝化/反硝化等也是土壤-春玉米系统中不可忽视的氮素损失途径。【结论】 我国春玉米主产区农民传统的氮肥用量偏高,增产效应不明显,氮肥损失风险加剧,尤其是氨挥发损失较大,氮肥的优化潜力高达20%～33%,相当于可减少施氮N 50～100 kg/hm²。

【目的】根系是玉米吸收氮素营养的主要器官。在大田条件下,对夏玉米根系生长分布、根系与土壤硝态氮空间吻合度对不同水氮处理的响应,以及根系与土壤硝态氮空间吻合度指标的有效性进行研究,用以了解其时空分布及与土壤氮分布的吻合情况对玉米氮素吸收利用的影响。【方法】2011—2015年,设置不灌水+不施氮（W0N0）、不灌水+300 kg N·hm^-2（W0N1）、不灌水+360 kg N·hm^-2（W0N2）、大喇叭口期灌水+不施氮（W1N0）、大喇叭口期灌水+300 kg N·hm^-2（W1N1）、大喇叭口期灌水+360 kg N·hm^-2（W1N2）共6个水氮处理。各施氮处理下拔节期施氮30%、大喇叭口期施氮70%。大喇叭口期灌水量为750 m³·hm^-2。在2015年玉米生长季,分别于玉米拔节期、大喇叭口期、吐丝期、吐丝后20 d和成熟期在玉米种植行和行间采集0—50 cm土体样品（每10 cm一层）,测定夏玉米根长密度、根干重密度、土壤硝态氮含量,并计算根系与土壤硝态氮空间吻合度。在成熟期采集植株样品,分析玉米氮素吸收量。【结果】随着玉米生育进程,种植行和行间0—50 cm土壤剖面夏玉米根长密度、根干重密度和硝态氮含量均表现出先升高后降低的趋势,根长密度和根干重密度峰值出现在吐丝后20 d,而土壤硝态氮含量峰值出现在大喇叭口期。在0—360 kg·hm^-2的范围内,夏玉米根长密度和吐丝期之前土壤硝态氮含量随施氮量的增加而增加,但玉米根干重密度和吐丝期之后土壤硝态氮含量先升高后降低,峰值出现在施氮300 kg·hm^-2处理。大喇叭口期灌水可以提高夏玉米生育后期根长密度和根干重密度,但降低了土壤硝态氮含量。随着土层加深,种植行夏玉米根长密度与土壤硝态氮空间吻合度（RLD1-N）以及根干重密度与土壤硝态氮空间吻合度（RWD1-N）总体呈降低趋势,行间夏玉米根长密度与土壤硝态氮空间吻合度（RLD2-N）以及根干重密度与土壤硝态氮空间吻合度（RWD2-N）总体呈先增加后降低趋势,峰值出现在10—30 cm土层。随着玉米生育进程,各土层RLD1-N、RWD1-N和RWD2-N以及0—40 cm土层RLD2-N呈先升高后降低变化趋势。与不施氮处理相比,施用氮肥提高了RLD1-N、RLD2-N、RWD1-N和RWD2-N。施氮量从300 kg·hm^-2增加至360 kg·hm^-2时,降低了0—30 cm土层RLD2-N、0—20 cm土层RWD1-N以及拔节至吐丝期间RLD1-N和0—20 cm土层RWD2-N,提高了40—50 cm土层RLD2-N、20—50 cm土层RWD1-N以及吐丝期之后的RLD1-N和RWD2-N。夏玉米种植行和行间根长密度和根干重密度与其硝态氮含量的吻合度与产量极显著正相关,但与氮素利用效率极显著负相关,且其相关性优于根长密度和根干重密度与产量及氮素利用效率的相关性。【结论】在大田条件下,施用氮肥可以提高夏玉米根长密度、根干重密度、土壤硝态氮含量以及夏玉米根系与土壤硝态氮空间吻合度。但施氮量超过300 kg·hm^-2时会降低夏玉米生育前期上部土层的夏玉米根系与土壤硝态氮空间吻合度。根系与土壤硝态氮空间吻合度可以作为研究夏玉米氮素利用效率的有效指标。

Poor soil and drought stress are common in semiarid areas of China, but maize has a high demand for nitrogen (N) and water. Maize production using the technique of double ridges and furrows mulched with plastic film are being rapidly adopted due to significant increases in yield and water use efficiency (WUE) in these areas. This paper studied N use and water balance of maize crops under double ridges and furrows mulched with plastic-film systems in a semiarid environment over four growing seasons from 2007 to 2010. To improve precipitation storage in the non-growing season, the whole-year plastic-film mulching technique was used. There were six treatments which had 0, 70, 140, 280, 420 or 560 kg N ha(-1) applied in every year for maize. In April 2011, spring wheat was planted in flat plots without fertilizer or mulch following four years of maize cultivation. After four years, all treatments not only maintained soil water balance in the 0-200 cm soil layer but soil water content also increased in the 0-160 cm soil layer compared to values before maize sowing in April 2007. However, under similar precipitation and only one season of spring wheat, soil water content in the 0-160 cm soil layer sharply decreased in all treatments compared to values before sowing in April 2011. Over the four years of maize cultivation, average yield in all treatments ranged from 4071 to 6676 kg ha(-1) and WUE ranged from 18.2 to 28.2 kg ha(-1) mm(-1). In 2011, the yield of spring wheat in all treatments ranged from 763 to 1260 kg ha(-1) and WUE from 3.5 to 6.5 kg ha(-1) mm(-1). The potential maximum grain yield for maize was 6784 kg ha(-1) with 360 kg N ha(-1) applied for four years, but considerable NO3-N accumulated in the soil profile. A lesser application (110 kg N ha(-1)) to this tillage system yielded in 82% of the maximum, increased nitrogen use efficiency and mitigated the risk of nitrogen loss from the system. This study suggests that double ridge-furrow and whole-year plastic-film mulching could sustain high grain yields in maize with approximately 110 kg N ha(-1) and maintain soil water balance when annual precipitation is >273 mm in this semiarid environment. (C) 2013 Elsevier B.V.