Enhancement of nitrogen release properties of urea–kaolinite fertilizer with chitosan binder

The use of controlled release fertilizer (CRF) has become a new trend to minimize environmental pollution. In this study, urea–kaolinite containing 20 wt% urea after one hour dry grinding was mixed with different concentrations of chitosan as a binder to prepare nitrogen-based CRF. Fourier transform infrared spectroscopy confirmed the hydrogen bonding between urea and kaolinite. Covalent interaction between urea–kaolinite and chitosan make the granules stronger. The nitrogen release was measured in 5 days interval using a diacetylmonoxime calorimetric method at a wavelength of 527 nm. The results illustrated that by increasing the chitosan concentration from 3 to 7.5%, nitrogen release decreased from 41.23 to 25.25% after one day and from 77.31 to 59.27% after 30 days incubation in water. Compressive stress at break tests confirmed that granules with chitosan 6% had the highest resistance and were chosen for ammonia volatilization tests. Ammonia volatilization was carried out using the forced-draft technique for a period of 10 weeks. The results showed that the total amount of ammonia loss for conventional urea fertilizer and urea–kaolinite–chitosan granules was 68.63 and 56.75%, respectively. This controlled release product could be applied in agricultural crop production purpose due to its controlled solubility in the soil, high nutrient use efficiency and potential economic benefits.     

Gaseous nitrogen emmissions from undisturbed terrestrial ecosystems: An assessment of their impacts on local and global nitrogen budgets

There is increasing interest in the importance of nitrogen gas emissions from natural (non-agricultural) ecosystems with respect to local as well as global nitrogen budgets and with respect to the effects of nitrogen oxides on atmospheric ozone levels and global warming. The volatile forms of nitrogen of common interest are ammonia (NH₃), nitrous oxide, (N₂O), dinitrogen (N₂), and NO_x (principally NO + NO₂). It is often difficult to attribute emissions of these compounds from soils to a single process because they are produced by a variety of common biogeochemical mechanisms. Although environmental conditions in the soil often appear to favor nitrogen gas emissions, the potential nitrogen gas emission rate from undisturbed ecosystems is rarely approached. The best estimates to date suggest that nitrogen gas emission rates from undisturbed ecosystems typically range from > 1 to perhaps 10 or 20 kg N ha^-1 yr^-1. Under certain conditions, however, emission rates may be much higher. For example, excreta from animals in grasslands may elevate ammonia volatilization up to 100 kg N ha^-1 yr^-1 depending on grazer density; tidal input of nutrients to coastal wetlands may support denitrification rates of several hundred kg N ha^-1 yr^-1 . Excepting such cases, gaseous nitrogen losses are probably a small component of the local nitrogen budget in most undisturbed ecosystems. However, emissions from undisturbed soils are an important component of the global source strengths for (N₂O + N₂), N₂O and NO_x (50%, 21%, and 10% respectively). Emission rates of N₂O from natural ecosystems are higher than assumed previously by perhaps 10 times. Large-scale disturbance may have a stimulatory effect on nitrogen emission rates which could have important effects on global nitrogen budgets. There is a need for more sophisticated methods to account for natural temporal and spatial variations of emissions rates, to more accurately and precisely assess their global source strengths.     

三江平原典型小叶章湿地土壤氨挥发特征及影响因素

采用通气法对三江平原典型草甸小叶章湿地和沼泽化草甸小叶章湿地土壤的氨挥发进行了原位测定,并对其主要影响因素进行了分析。结果表明,二者的氨挥发速率在生长季内的变化趋势基本一致,7月中旬前出现两次挥发高峰和一次低值,之后整体呈严格单调下降趋势,后者的氨挥发速率较高,平均为前者的1.35±0.53倍;二者累计氨挥发量的变化趋势也基本一致,7月中旬前增加迅速,且值比较接近;之后增加缓慢,但其值发生明显分异,表现为后者大于前者;生长季内,典型草甸小叶章湿地土壤的氨挥发总量为6.35 kg N.hm-2,而沼泽化草甸小叶章湿地则为6.87 kg N.hm-2,二者之比为1∶1.08;氮素物质基础不是影响二者氨挥发过程的重要限制因素,大气温度及其所引起的其它温度波动是影响氨挥发速率变化的重要因素;降水及土壤水分波动与散失是引起氨挥发速率局部波动的重要原因;土壤pH和质地是导致氨挥发速率普遍较低的根本原因;而各种因素综合作用的结果则是引起二者氨挥发速率和氨挥发量变化及差异的主要原因。     

生物炭对农田土壤氨挥发的影响机制研究进展

降低土壤氨挥发量是农田生态系统中减少土壤氮素损失、提高氮肥利用率的关键途径之一。生物炭具有独特的理化性质,施入土壤后可改变土壤理化性状,影响土壤氮素循环,并对农田土壤中氨挥发产生重要的影响。本文首先介绍了稻田和旱田两种土地利用方式下农田氨挥发过程及其影响因素(气候条件、土壤环境、施肥管理等);其次,重点综述了生物炭对农田生态系统氨挥发影响的研究进展,并从物理吸附机制、气液平衡机制、生物化学过程调节机制等方面探讨了生物炭介入下农田土壤氨挥发的响应机制,认为土壤氨挥发减排的响应主要是基于生物炭表面含氧官能团对土壤NH₄⁺和NH₃的吸附作用及促进土壤硝化作用;而生物炭增加土壤氨挥发排放主要与生物炭提高土壤pH值和透气性、增强土壤有机氮矿化微生物活性有关。最后,对生物炭减少土壤氨挥发、提高氮肥利用率的研究方向进行了展望。     

The volatilization of ammonia from cattle urine applied to soils as influenced by soil properties

The amounts of ammonia volatilized, following the application of cattle urine to 22 soils, were measured in the laboratory during an incubation period of 10 days. The urine contained 12.0 g N dm^-3 and was applied to small columns of soil at a rate equivalent to 26.5 g N m^-2. The soils were from fields of both grassland and arable cultivation and varied widely in properties. Ammonia volatilization ranged from 6.8 to 41.3% of the total urinary N, with a mean value of 26.4%. The soil property most closely related to the extent of volatilization was cation exchange capacity (CEC), and this was so whether all 22 soils were considered together or whether the 14 grassland and 8 arable soils were considered separately. In general, the higher the CEC the less the amount of ammonia volatilized. However, for a given value of CEC, volatilization tended to be greater from a grassland than from an arable soil. The pH of a soil/urine mixture measured after 24 hours was also quite closely correlated with the amount of ammonia volatilized, but the initial pH and titratable acidity of the soil were poorly correlated with ammonia volatilization. ei]H Marschner ei]H Lambers     

不同包膜控释尿素对农田土壤氨挥发的影响

为了探索包膜控释尿素土壤氨挥发损失规律特征和提高肥料氮素利用率,采用小麦玉米轮作田间试验,通过与普通尿素进行对比,运用土壤氨挥发原位测定方法——通气法系统研究了硫包膜和树脂包膜控释尿素的施用对小麦玉米轮作农田土壤氨挥发的影响.研究结果表明:在两种施氮量水平下(210 kg/hm2和300 kg/hm2),与普通尿素相比,硫包膜和树脂包膜控释尿素在小麦基肥期、小麦追肥期和玉米施肥期的施用均减少了土壤氨挥发的累积损失量,分别达35.1％-54.3％、59.6％-75.2％、65.6％-98.1％;有效降低了土壤氨挥发通量峰值且延迟其出现时间3-8 d,并能延缓土壤氨挥发主要阶段的时间分别为4-12 d、5-12 d.在小麦玉米轮作周年中,控释尿素土壤氨挥发累积损失量为28.39-43.35 kg/hm2,土壤氨挥发损失率为4.48％-5.63％,控释尿素时段土壤氨挥发通量比普通尿素降低了51.0％-70.8％;且树脂包膜控释尿素的施用降低小麦玉米轮作农田土壤氨挥发的效果优于硫包膜控释尿素.     

Contemporary and pre-industrial global reactive nitrogen budgets

Increases and expansion of anthropogenic emissions of both oxidized nitrogen compounds, NO_x, and a reduced nitrogen compound, NH₃, have driven an increase in nitrogen deposition. We estimate global NO_x and NH₃ emissions and use a model of the global troposphere, MOGUNTIA, to examine the pre-industrial and contemporary quantities and spatial patterns of wet and dry NO_y and NH_x deposition. Pre-industrial wet plus dry NO_x and NH_x deposition was greatest for tropical ecosystems, related to soil emissions, biomass burning and lightning emissions. Contemporary NO_y+NH_x wet and dry deposition onto Northern Hemisphere (NH) temperate ecosystems averages more than four times that of preindustrial N deposition and far exceeds contemporary tropical N deposition. All temperate and tropical biomes receive more N via deposition today than pre-industrially. Comparison of contemporary wet deposition model estimates to measurements of wet deposition reveal that modeled and measured wet deposition for both NO ₃ ^– and NH ₄ ⁺ were quite similar over the U.S. Over Western Europe, the model tended to underestimate wet deposition of NO ₃ ^– and NH ₄ ⁺ but bulk deposition measurements were comparable to modeled total deposition. For the U.S. and Western Europe, we also estimated N emission and deposition budgets. In the U.S., estimated emissions exceed interpolated total deposition by 3-6 Tg N, suggesting that substantial N is transported offshore and/or the remote and rural location of the sites may fail to capture the deposition of urban emissions. In Europe, by contrast, interpolated total N deposition balances estimated emissions within the uncertainty of each.Abbreviations EMEP European Monitoring and Evaluation Program - GEIA Global Emissions Inventory Activity - NADP/NTN National Atmospheric Deposition Program/National Trends Network in the US - NH Northern Hemisphere - NH_x=NH₃+NH ₊ ⁴ NO_x=NO+NO₂ NO_y total odd nitrogen=NO_x+HNO₃+HONO+HO₂NO₂+NO₃+radical (NO₃ ^.)+Peroxyacetyl nitrates+N₂O₅+organic nitrates - SH Southern Hemisphere - Gg 10⁹ g - Tg 10¹² g     

Low degradable protein supply to increase nitrogen efficiency in lactating dairy cows and reduce environmental impacts at barn level

Generally, <30% of dairy cattle’s nitrogen intake is retained in milk. Large amounts of nitrogen are excreted in manure, especially in urine, with damaging impacts on the environment. This study explores the effect of lowering dietary degradable nitrogen supplies – while maintaining metabolisable protein – on dairy cows’ performance, nitrogen use efficiency and gas emissions (NH₃, N₂O, CH₄) at barn level with tied animals. Two dietary N concentrations (CP: 12% DM for LowN; 18% DM for HighN) were offered to two groups of three lactating dairy cows in a split-plot design over four periods of 2 weeks. Diets were formulated to provide similar metabolisable protein supply, with degradable N either in deficit or in excess (PDIN of 84 and 114 g/kg DM for LowN and HighN, respectively). Cows ingested 0.8 kg DM/day less on the LowN diet, which was also 2.5% less digestible. Milk yield and composition were not significantly affected. N exported in milk was 5% lower (LowN: 129 g N/day; HighN: 136 g N/day; P<0.001) but milk protein yield was not significantly affected (LowN: 801 g/day; HighN: 823 g/day; P=0.10). Cows logically ingested less nitrogen on the LowN diet (LowN: 415 g N/day; HighN: 626 g N/day; P<0.001) resulting in a higher N use efficiency (N milk/N intake; LowN: 0.31; HighN: 0.22; P<0.001). N excreted in urine was almost four times lower on the LowN diet (LowN: 65 g N/day; HighN: 243 g N/day; P<0.001) while urinary urea N concentration was eightfold lower (LowN: 4.6 g/l; HighN: 22.9 g/l; P<0.001). Ammonia emission (expressed in g/h in order to remove periods of the day with potential interferences with volatile molecules from feed) was also lower on the LowN diet (LowN: 1.03 g/h per cow; HighN: 1.25 g/h per cow; P<0.05). Greenhouse gas emissions (N₂O and CH₄) at barn level were not significantly affected by the amount of dietary N. Offering low amounts of degradable protein with suitable metabolisable protein amounts to cattle improved nitrogen use efficiency and lowered ammonia emissions at barn level. This strategy would, however, need to be validated for longer periods, other housing systems (free stall barns) and at farm level including all stages of manure management.     

控释肥料与普通氮肥混施对春白菜产量、品质和氮素损失的影响

在京郊露地生产条件下,研究了控释肥料与速效化肥混配施用对春白菜产量、品质、氨挥发、土壤硝态氮累积和淋失的影响.结果表明：与习惯施肥处理（施N 300 kg·hm^-2）相比,控释肥料与普通化肥按纯氮比2∶1混配施用（共施N 150 kg·hm^-2）没有造成白菜减产,并显著降低了菜叶中硝酸盐和有机酸含量;与半量施肥处理(施N 150 kg·hm^-2)相比,控释肥与化肥混施处理产量和叶片硝酸盐含量无显著差异.控释肥与化肥混施处理提高了白菜氮肥利用率,减少了N₃-N淋失量和氨挥发总量.白菜收获后,控释肥与化肥混施处理在20～40、60～80、80～100 cm土层的NO₃^--N含量显著低于习惯施肥处理.     

森林生态系统碳循环对全球氮沉降的响应

森林土壤和植被储存着全球陆地生态系统大约46%的碳,在全球碳平衡中起着非常重要的作用。过去几十年来,森林生态系统的碳循环和碳吸存受到了全球氮沉降的深刻影响,因为氮沉降改变了陆地生态系统的生产力和生物量积累。以欧洲和北美温带森林区域开展的研究为基础,综述了氮沉降对植物光合作用、土壤呼吸、土壤DOM及林木生长的影响特征和机理,探讨了森林生态系统碳动态对氮沉降响应的不确定性因素。热带森林C、N循环与大部分温带森林不同,人为输入的氮对热带生态系统过程的影响也可能不同,因此指出了在热带地区开展碳氮循环耦合研究的必要性和紧迫性。     

High nitrogen isotope ratio for soils of seabird rookeries

Soils from rookeries of penguin, of gull, and of albatross were examined for their nitrogen isotope ratio. The ratio was far higher than any so far reported for soils. Furthermore, there was an apparent dependence of the ratio on the latitude of rookery locations. The high ratio seemed to have had resulted from a relatively high ratio for incoming nitrogen to the rookeries, and from the large fractionation factor during the ammonia volatilization from the rookeries. The isotope ratio for ammonium nitrogen of the penguin rookery soils averaged 45 per mil, while that of the gull rookery soils gave the mean of 27 per mil during the breeding season of the birds. Soils of gull rookeries and of albatross rookery gave, on the average, a similar ratio of 17 per mil for Kjeldahl nitrogen, though its content of soils of gull rookeries was nearly two orders of magnitude higher than that of albatross rookery. Soils from penguin rookery showed the ratio of 32 per mil for Kjeldahl nitrogen, the enrichment of¹⁵N being two and a half times as large as that for soils of other rookeries.     

控释尿素条施深度对鲜食玉米田间氨挥发和氮肥利用率的影响

为提高鲜食玉米一次性施肥的氮肥利用率并降低氮肥的环境影响,通过田间试验,以不施氮处理为对照(CK),研究了控释尿素不同条施深度(0、5、10、15、20 cm)对鲜食玉米田间土壤氨挥发特征、鲜穗产量和氮肥利用率的影响. 结果表明: 玉米种植带和宽行非施肥带的土壤氨挥发主要发生在施肥后的前2周,而窄行施肥带的土壤氨挥发在施肥后持续约1个月. 与CK相比,控释尿素表施(0 cm)处理不仅大幅度地提高了窄行施肥带的氨挥发损失量,同时也显著增加了玉米种植带和宽行非施肥带的氨挥发损失量. 不同深度施肥处理全生育期土壤氨挥发损失总量差异较大,为3.1～25.5 kg N·hm^-2,占施氮量的1.7%～14.2%.其中控释尿素条施10、15和20 cm深度处理的全生育期土壤氨挥发损失总量相差不大,分别较表施(0 cm)和浅施(5 cm)处理显著降低了85.9%～87.8%和67.0%～71.6%. 在一定范围内增加控释尿素条施深度有利于提高鲜穗产量、植株氮积累量以及氮肥偏生产力、氮肥农学利用率和氮肥表观利用率,各指标均以15 cm深度处理最高. 综上所述,控释尿素合理深施可以显著降低氨挥发损失,提高鲜穗产量和氮肥利用效率,本研究条件下控释尿素的最适宜施用深度为15 cm.     

控释肥对夏玉米产量及田间氨挥发和氮素利用率的影响

在大田条件下研究了树脂包膜控释肥（CRF）和硫包膜控释肥（SCF）对夏玉米产量、田间氨挥发及氮肥利用率的影响.结果表明：控释肥能显著提高玉米产量.在相同施肥量（N、P、K量相同）情况下,全量控释肥CRF(1428 kg·hm^-2)和SCF（1668 kg·hm^-2）分别比全量普通复合肥CCF（1260 kg·hm^-2）增产13.15%和14.15%;控释肥施肥量减少25%（CRF 1071 kg·hm^-2;SCF 1251 kg·hm^-2）时,分别比CCF增产9.69%和10.04%;控释肥施肥量减少50%时（CRF 714 kg·hm^-2;SCF 834 kg·hm^-2）,其产量与CCF无显著差异.对夏玉米田间土壤原位氨挥发进行研究表明,控释肥处理氨挥发速率上升缓慢,最大挥发高峰出现时间比普通肥处理晚7 d,土壤氨挥发量在0.78～4.43 kg N·hm^-2,比普通肥处理(9.11 kg N·hm^-2)减少51.34%～91.34%.控释肥的氮肥利用率和农学效率也均显著高于普通肥处理.     

Dry nitrogen deposition estimates over a forest experiencing free air CO2 enrichment

The quantification of atmospheric additions of nitrogen (N) to an ecosystem is often desirable, but difficult for many locations including many ecological manipulation experiments. Ideal methodologies for the complete and chemically speciated quantification of dry N deposition (e.g. tunable diode laser absorption spectrometer, thermal‐dissociation laser‐induced fluorescence) are expensive, technologically challenging to maintain, and rarely colocated with important global change manipulation experiments. Here we present an alternative method for obtaining an approximation of total N deposition using short‐term eddy flux and concentration measurements, annual regional concentration estimates, and modeling for the Duke Experimental Forest. The motivation for generating estimates for this location was to inform the long‐term elevated CO₂ experiment conducted at Duke Forest. We estimated the total annual atmospheric N deposition to the forest to be 13.7 kg N ha^?1. Of this total, ～58% was in dry‐deposited forms. Surprisingly, and contrary to some previous predictions, nitric acid (HNO₃) was not the dominant portion of the total dry‐deposited N, implying strongly that other forms of gaseous N like organic peroxy and alkyl nitrate compounds are a significant portion of the total flux. Furthermore, this study sheds light on the completeness of the estimates derived from Clean Air Status and Trends Network (CASTNet) and other dry deposition networks. CASTNet does not measure organic forms of dry deposition. In fact, CASTNet only quantifies HNO₃ in the gas phase and may significantly underestimate total N deposition in many environments.     

不同施肥与灌水量对槟榔土壤氨挥发的影响

利用通气法田间原位试验,研究了不同施肥模式、灌溉量对槟榔土壤氨挥发速率和挥发量的影响。结果表明：槟榔恢复期和出花期追肥灌水后,不同施肥处理均在第3天出现氨挥发速率峰值（0.50-3.42 kg.hm-2.d-1）,而后迅速下降并进入低挥发阶段。出花期氨挥发速率峰值（1.50-4.42 kg.hm-2.d-1）比恢复期氨挥发速率峰值明显高。灌水量小(300 m3. hm-2)的氨挥发率和总量比灌水量大(600 m3. hm-2)的明显减小。在同一氮水平下,有机质含量较低的氨挥发率较高。在同一有机质含量条件,氨挥发率随着N肥含量增加而升高。与单施N肥处理相比,有机肥与N肥配施可明显减少氨挥发速率和总量,可减少氮损失。     

A global assessment of forest surface albedo and its relationships with climate and atmospheric nitrogen deposition

We present a global assessment of the relationships between the short‐wave surface albedo of forests, derived from the MODIS satellite instrument product at 0.5° spatial resolution, with simulated atmospheric nitrogen deposition rates (N_dep), and climatic variables (mean annual temperature T_m and total annual precipitation P), compiled at the same spatial resolution. The analysis was performed on the following five forest plant functional types (PFTs): evergreen needle‐leaf forests (ENF); evergreen broad‐leaf forests (EBF); deciduous needle‐leaf forests (DNF); deciduous broad‐leaf forests (DBF); and mixed‐forests (MF). Generalized additive models (GAMs) were applied in the exploratory analysis to assess the functional nature of short‐wave surface albedo relations to environmental variables. The analysis showed evident correlations of albedo with environmental predictors when data were pooled across PFTs: T_m and N_dep displayed a positive relationship with forest albedo, while a negative relationship was detected with P. These correlations are primarily due to surface albedo differences between conifer and broad‐leaf species, and different species geographical distributions. However, the analysis performed within individual PFTs, strengthened by attempts to select ‘pure’ pixels in terms of species composition, showed significant correlations with annual precipitation and nitrogen deposition, pointing toward the potential effect of environmental variables on forest surface albedo at the ecosystem level. Overall, our global assessment emphasizes the importance of elucidating the ecological mechanisms that link environmental conditions and forest canopy properties for an improved parameterization of surface albedo in climate models.