Ammonia volatilization from grassland receiving nitrogen fertilizer and rotationally grazed by dairy cattle

The micrometeorological mass balance method was used to measure ammonia (NH₃) volatilization from rotationally grazed swards throughout the 1987 and 1988 growing seasons. In both years the swards were dressed with calcium ammonium nitrate (CAN) split over 7 dressings. In 1987 the sward received a total of 550 kg N ha^–1, in 1988 a total of 550 or 250 kg N ha^–1. For the 550 kg N ha^–1 treatments there were 8 and 9 grazing cycles, respectively, in 1987 and 1988 and 7 for the 250 kg N ha^–1 treatment. Losses from the 550 N sward were 42.2 and 39.2 kg N ha^–1 in 1987 and 1988, respectively; this was equivalent to 8.5 and 7.7% of the N returned to the sward in the excreta of the grazing cattle. The NH₃ loss from the 250N sward was 8.1 kg N ha^–1 in 1988, which was equivalent to 3.1% of the N returned to the sward in excreta during the growing season. There was a wide variation in NH₃ volatilization between the individual grazing periods. This indicates the necessity of continued measurements throughout the growing season to obtain reliable data on NH₃ volatilization. Soil humidity is suggested to be a key factor, because emissions were high from wet soil, and low from drier soil. Results of a Monte Carlo simulation study showed that the measured NH₃ loss from the 250 and 550 N swards had a standard deviation of 13 and 5% of the mean, respectively.     

Effect of magnesium sulphate addition to urea on nitrogen loss due to ammonia volatilization

Fertilizer was applied as urea alone or as a mixture of urea and magnesium sulphate (MgSO₄·1H₂O) to study the effect on ammonia volatilization under laboratory conditions in relation to soil texture, N:Mg ratio, air flow rate, fertilizer form (solid or liquid) and organic material. When the mixture of urea and magnesium sulphate (UMM) was applied at a ratio of 1:0.21, significantly lower NH₃-N losses than from urea were found in 2 of 6 soils, and 4 soils showed a similar tendency. Increasing the N:Mg ratio to 1:0.5 resulted in significantly lower NH₃-N loss. Lower air flow rates reduced ammonia loss from UMM more than from urea alone. The effectiveness of UMM over urea was not improved in the liquid form. Increase of organic material had no influence on NH₃-N loss from urea alone or UMM.     

Lowering ammonia volatilization losses from urea application by activation of nitrification process

The aim of this work was to lower ammonia volatilization losses by increasing the rate of nitrification. This was achieved by eliminating the gap in timing between urea hydrolysis and ammonium nitrification. Soils were pretreated with a small amount of ammonium salt which led to the activation of the nitrification process. When nitrification passed its lag period, urea was applied to the soils. Ammonium produced by urea hydrolysis was quickly oxidized into nitrate and did not accumulate in the soil. This resulted in decreased ammonium concentrations in soil, and consequently, in decreased ammonia volatilization losses.This report is part of a doctoral thesis by the first author.     

Dynamics of ammonia volatilization from simulated urine patches and aqueous urea applied to pasture. II. Theoretical derivation of a simplified model

Theoretical considerations for the development of a simplified model for predicting volatilization losses of ammonia gas (NH_3(g)) from the urine patches of grazing herbivores in a pasture ecosystem are presented. The volatilization of NH_3(g) is treated as a physico-chemical phenomenon based on the soil solution chemistry of urine patches to develop a general equation to describe the rate of volatilization from a pasture surface. A semi-empirical approach was then used in which published data define typical limits for the parameters appearing in the volatilization equation. This led to the simplification of the general volatilization equation into a more useable and more readily verifiable form.The dominant factor in determining the rate of volatilization of NH_3(g) was shown to be the soil surface pH. To better understand the dynamics of pH changes within urine patches, the more extensive literature dealing with volatilization losses from flooded soils was reviewed. From the apparent similarities between the two systems a procedure was described by which a careful monitoring of soil surface pH as a function of time could be used to solve the simplified equation.To calculate NH_3(g) fluxes this model requires the following as input data: a knowledge of the disposition of the applied-N within the soil profile; the rate of urea hydrolysis in the topsoil; and soil surface pH and temperature measurements throughout the duration of a volatilization event.     

Time and mode of nitrogen fertilizer application to tropical wetland rice

In experiments with transplanted rice (Oryza sativa L.) at the International Rice Research Institute, Philippines, two methods of split application of urea and ammonium sulfate were compared with deep, point placement (10 cm) of urea supergranules and broadcast application of a slow-release fertilizer sulfur-coated urea (SCU). Comparisons were made in the wet and dry seasons and were based on rice yield and N uptake. Urea- and ammonium-N concentrations and pH of the floodwater were measured to aid interpretation of the results.Split applications of urea were generally less efficient than ammonium sulfate. The split in which the initial fertilizer dose was broadcast and incorporated into the soil before transplanting was more effective than the split in which the fertilizer was broadcast directly into the floodwater 21 days after transplanting. Both split applications were inferior to the urea supergranules and SCU, in terms of both yield and N uptake efficiency; average apparent N recoveries ranged from 30% for the delayed split urea to 80% for the urea supergranule.Broadcast applications of urea and ammonium sulfate produced high floodwater concentrations of urea- and ammonium-N, which fell to zero within 4–5 days. Floodwater pH was as high as 9.3 and fluctuated diurnally due to heavy algal growth. Ammonia volatilization and algal immobilization of N in the floodwater were probably responsible for the poor efficiency of the split applications; the supergranules and SCU on the other hand produced low floodwater N concentrations and were efficiently used by the rice crop.     

Effects of initial soil calcium content on ammonia losses from surface-applied urea and calcium-urea

Ammonia loss from surface-applied urea occurs because urea hydrolysis increases the pH of the placement site microenvironment. Addition of Ca-salts with urea will control or reduce the microsite pH, thus reducing NH₃ losses. The degree of Ca-saturation of the cation exchange sites may influence the ratio of calcium:urea required to control ammonia loss. A laboratory study was conducted to determine if adsorbed Ca or CaCO₃ additions (acid soils only) had a measureable impact on Ca control of NH₃ loss from surface applied urea at various Ca:urea ratios.With urea alone applied to the soil surface varying the adsorbed Ca content of the treatment soil did not influence NH₃ loss. The addition of CaCl₂ with urea on the same pretreated soils generally resulted in NH₃ losses reflecting the initial pH of the soil. The Ca-saturated acid soils and those acid soils receiving CaCO₃ had higher NH₃ losses than untreated soils in the presence of urea with soluble CaCl₂. It was noted that increasing the calcium:urea ratios progressively depressed the NH₃ loss from all soils. Increasing the percent Na-saturation of the calcareous Harkey soil to 25 and 50% (ESP) reduced Ca control of NH₃ loss due to Ca being exchanged for Na on the cation exchange sites.Inclusion of CaCl₂ with the urea mixture on the surface of the pretreated acid soils resulted in stepwise differences in NH₃ loss concuring with the increases in pretreatment soil pH values (differing exchangeable Ca content). Other parameters that influence the amount of NH₃ loss, such as acidic buffer capacity and CEC, appeared more important than anticipated for control of NH₃ loss with the calcium:urea mixture. On Ca enriched soils the calcium:urea mixture was only slightly less effective in its ability to control NH₃ losses than on untreated soils.Contribution from the Texas Agric. Exp. Sta., Texas A&M University System, College Station, TX 77843, USA     

The influence of sward mass,defoliation and watering on ammonia volatilization losses from an Italian ryegrass sward topdressed with urea

Using intact pasture sods with 0.15m² surface area and sealed in volatilization chambers, the influence of the mass of herbage on the ammonia volatilization losses following a surface application of urea was determined. Ammonia volatilization loss increased as sward mass decreased. This effect was still evident in poorly established pastures.Under drying conditions the timing of defoliation and water applications relative to the application of urea was also shown to influence ammonia volatilization patterns and magnitude of loss. Delaying defoliation promotes a reduction in ammonia volatilization losses while delayed watering resulted in increased losses.     

Dynamics of ammonia volatilization from simulated urine patches and aqueous urea applied to pasture I. Field experiments

Ammonia (NH₃) volatilization losses from simulated sheep urine patches in a perennial ryegrass (Lolium perenne L.)/white clover (Trifolium repens L.) pasture in New Zealand were measured in the field during the summer, autumn and winter periods. An enclosure technique was used with microplots (23 cm diameter) receiving either sheep urine or aqueous urea at rates equivalent to 500 kg N ha^–1 and monitored continuously until measured losses decreased to 0.5% per day. Mean volatilization losses for urine treated plots were 22.2% of the applied N in summer, 24.6% in autumn and 12.2% in winter. Corresponding losses for the urea treated plots were 17.9%, 28.9% and 8.5%. Differences between these two N sources were not significant although the seasonal differences were significant (P 0.05). Changes in NH₃ gas fluxes were found to be related to measured changes in soil pH and air temperature. Two repeated applications of urine or aqueous urea to the same microplot resulted in significantly greater subsequent volatilization losses averaging 29.6% from the second and 37.5% from the third application.Most of the applied N was accounted for as either soil mineral N (NH ₄ ⁺ + NO ₃ ^- + NO ₂ ^- ) or NH_3(g) . Urea hydrolysis was rapid and obeyed the first order kinetics during the 24 hours following application. Calculated half-lives of urea in urine and aqueous urea were significantly different and were 3.0 and 4.7 h respectively during the summer and 4.7 and 12.0 h during the autumn.Implications of the results obtained to practical field situation together with the efficacy of the enclosure technique for measuring volatilization losses are discussed.     

用沉淀气浮法回收化肥厂废水中氨氮及机理研究

研究了沉淀气浮法回收化肥厂废水中氨氮的工艺及气浮药剂与沉淀物的作用机理。结果表明,用氯化镁和磷酸氢二钠作为沉淀剂时,pH值是重要的影响因素,pH值为10.5时氨氮沉淀率可达95%以上。气浮剂的用量是影响气浮效果的重要因素,在pH值为10.5,气浮剂十二酸钠用量为75mg/L时,气浮回收率可以达到96%以上。经X衍射分析表明,生产的沉淀物以晶态MgNH4PO·46H2O为主。经红外光谱分析表明,十二酸钠在磷酸铵镁表面发生化学吸附,从而使其表面疏水而上浮。     

Ammonia volatilization from urea as affected by the addition of iron pyrites and method of application

Laboratory incubations were conducted to determine the ammonia (NH₃) loss from urea as affected by the addition of coarse and ground (fine) pyrites at 1:1, 1:2 and 1:5 urea: pyrite (w/w) ratios and methods of application (surfaceapplication, incorporation and placement). Coarse pyrites (>-2mm) were not effective in reducing NH₃ loss from urea when surface applied even at the highest ratio of pyrite (15.9% vs 18.7% without pyrite). Ground pyrites (0.1–0.25 mm), in 1:1 ratio, had about 5% less NH₃ loss than the urea alone treatment. Higher ratios of pyrites reduced NH₃ loss much more. Ammonia losses were the most with surface-applied urea (18.9%) and the least (13.5%) when placed (2.5 cm) below the soil surface. Addition of ground pyrite to surface-applied urea (1:1 ratio) decreased the loss to 13.2%. Urea+pyrite placed below the soil surface had the least loss (9.8%). Results indicate that combined application of urea and fine pyrite could reduce NH₃ loss.     

Studies on the relationship between slurry pH,volatilization processes and the influence of acidifying additives

The mutual influence of slurry pH and volatilization processes on one hand, and the possibility of N conservation by the use of acidifying additives on the other, were investigated in static incubation experiments. The influence of the NH₃ and CO₂ volatilizations on slurry pH was studied by selectively supporting one or both processes. The addition of Ca²⁺ to slurry was compared to that of K⁺ and H⁺. The effects of Cl^–, SO ₄ ^2– and NO ₃ ^– as corresponding anions of Ca²⁺ on slurry pH as well as NH₃ and N₂O emissions were tested. The slurry pH (7.4) increased during incubation. When CO₂ volatilization was suppressed, the pH increase was reduced, and NH₃ volatilization was cut down by 50%. Ca²⁺ additions hardly influenced the initial slurry pH, but reduced the pH increases and NH₃ losses. Proton addition, in contrast, decreased slurry pH but did not decrease the subsequent pH rise. K⁺ had no effect on slurry pH and N losses. As compared to CaCl₂, CaSO₄ showed less effect on slurry pH and N losses. Ca(NO₃)₂ was nearly as effective as CaCl₂ in preventing NH₃ volatilization, but caused denitrification losses and elevated N₂O production. Titration curves of the different slurry treatments were used to interpret the results of the incubation experiments. In a microplot field experiment the NH₃ volatilization and slurry pH after surface application of slurry was measured. The acidifying and N conserving effects of Ca²⁺ and H⁺ additions were confirmed.     

The effect of urea pellet size and rate of application on ammonia volatilization and soil nitrogen dynamics

In a field experiment on deep, yellow, sandy soil near Badgingarra, Western Australia, the residual value of superphosphate applied one and two years previously was measured relative to freshly-applied superphosphate using yields of narrow-leafed lupin (Lupinus angustifolius), barley and wheat. In addition, soil samples were collected for measurement of bicarbonate-extractable soil P. This was also used to estimate the residual value of the superphosphate.For lupins and wheat, and for bicarbonate-extractable soil P, the residual value decreased with increasing level of application. For barley grain, the residual value was not significantly affected by the level of application.The decrease in residual value of superphosphate with increasing level of application is attributed to increased leaching of applied phosphorus (P) down the profile of the sandy soils as the level of application increases. This may reduce subsequent plant yields due to the delay in seedling roots reaching the P in the soil during the crucial early stages of plant growth.For lupins, the relationship between yield and the level of superphosphate applied was markedly sigmoidal. The relationship for wheat and barley was exponential. Consequently, at suboptimal levels of P application, lupins required about two to three times more P than wheat or barley to produce the same yield. However, lupins required less P to achieve near-maximum yield.     

尿素中添加腐植酸、黄腐酸、重过磷酸钙和氯化钾能抑制氨的挥发

该试验比较了不同混合物,尿素-重过磷酸钙-氯化钾、尿素-重过磷酸钙-氯化钾-腐植酸、尿素-重过磷酸钙-氯化钾-黄腐酸、尿素-重过磷酸钙-氯化钾-酸性混合物(黄腐酸+腐植酸)在对氨损失,土壤pH值,铵态氮和可利用硝态氮积累等方面的影响,以尿素单独施用作为对照。方法:在实验室条件下,利用一个封闭式动态空气流量系统来评估是否混有重过磷酸钙、氯化钾、腐植酸、黄腐酸的情况下尿素的有效性。氨损失、土壤pH值、土壤中铵态氮以及可利用硝态氮是由标准程序测定的。结果:与对照组(单独施用尿素)相比,处理尿素-重过磷酸钙-氯化钾,尿素-重过磷酸钙-氯化钾-腐植酸,尿素-重过磷酸钙-氯化钾-黄腐酸,尿素-重过磷酸钙-氯化钾-酸性混合物(黄腐酸+腐植酸)中氨损失明显地减少,减少率由12.92%、20.12%、25.94%达到100%,土壤中的铵态氮也有类似的变化。从所有的处理来看,只有尿素-重过磷酸钙-氯化钾-黄腐酸,尿素-重过磷酸钙-氯化钾-酸性混合物(腐植酸+黄腐酸)明显地积累了土壤中可利用硝态氮,这一结果与本研究中pH值的结果一致。结论:尿素、重过磷酸钙、氯化钾中混合腐植酸或者酸性的腐植酸和黄腐酸混合物能够显著减少氨损失。这项研究结果有助于提高尿素中N,P,K使用的有效性,同时减少环境污染。     

次氯酸钠处理电镀废水中氨氮及其ORP控制方式的研究

利用次氯酸钠处理电镀工业园区污水处理厂的生化出水,研究了反应时间、p H值和次氯酸钠投加量对氨氮去除效果的影响以及ORP的变化规律。结果表明,p H值在6~8之间,反应时间为10 min,次氯酸钠与氨氮的质量比为8∶1和9∶1时,出水氨氮的质量浓度分别小于15和8 mg/L,可满足GB 21900—2008《电镀污染物排放标准》中氨氮排放的要求。ORP变化和次氯酸钠的投加量有较好的规律性,并在实际工程中实现了ORP控制次氯酸钠的自动投加。     

增值尿素的氨挥发特征及其对土壤微生物量碳和脲酶活性的影响

通过向普通尿素中添加风化煤粉、腐植酸钾和脱盐液,利用熔融造粒工艺制备出普通尿素（U）、风化煤尿素（F U）、腐植酸尿素（H A U）、脱盐液尿素（T U）3个增值尿素试验产品,在25℃条件下,进行土壤培养试验,研究了增值尿素的氨挥发特征及其对土壤微生物量碳、脲酶活性的影响。结果表明,与普通尿素相比,各增值尿素氨挥发累积量降低29.52%～39.78%,延迟了氨挥发的峰值;各增值尿素处理,在培养的前7天内土壤的脲酶活性降低,延缓了尿素态氮在土壤的转化速率;延缓了土壤微生物量碳峰值出现时间;风化煤和腐植酸尿素处理在整个培养期内表现处理了较好的稳定性,减少氨挥发效果明显。     

Effect of urease,nitrification and algal inhibitors on ammonia loss and grain yield of flooded rice in Thailand

This paper reports a study, in a flooded rice field in Thailand, on the effects of two urease inhibitors, cyclohexylphosphorictriamide (CHPT) and N-(n-butyl)phosphorictriamide (NBPTO), the nitrification inhibitor phenylacetylene and an algicide treatment, consisting of alternate additions of copper sulfate and terbutryn at ~3 day intervals, on nitrogen (N) transformations and transfers, and grain yield. The addition of algicide reduced the growth of algae and maintained the pH of the floodwater below that of the control for 11 days. Judging from the ammoniacal N concentrations of the floodwater, phenylacetylene inhibited nitrification. The two urease inhibitors markedly reduced urea hydrolysis and CHPT was more effective than NBPTO. Addition of CHPT maintained the ammoniacal N concentration of the floodwater below 2 g m^–3 for 11 days and reduced ammonia loss by ~90%. All urease inhibitor treatments in combination with algicide and / or nitrification inhibitor significantly (p < 0.05) increased the recovery of applied N by the plant. Addition of NBPTO or CHPT in combination with phenylacetylene and algicide resulted in a 2 or 3 fold increase of applied N in the grain, and significantly (p < 0.05) increased grain yield.     

Effect of the timing and rate of nitrogen fertilization on the growth and recovery of fertilizer nitrogen within the potato (Solanum tuberosum L.) crop

The effect of the timing of N fertilizer application on the uptake and partitioning of N within the crop and the yield of tubers has been studied in two experiments. In 1985 either none, 8 or 12 g N m^–2 was applied and in 1986 none, 12 or 18 g N m^–2. Fertilizer N was applied either at planting, around the time of tuber initiation or half at planting and the remainder in four foliar sprays of urea during tuber bulking.¹⁵N-labelled fertilizer was applied to measure the recovery of fertilizer N in the crops.There was an apparent pre-emergence loss of nitrate from the soil when N was applied at planting in 1986, thereby reducing the efficiency of fertilizer use. Applying the N at tuber initiation delayed and reduced the accumulation of N in the canopy compared with crops receiving all their fertilizer at planting. Foliar sprays of urea slightly increased both tuber yields and tuber N contents when compared to a single application at planting. The proportion of the fertilizer N recovered in the crop was little affected by the rate of N application, but a greater proportion of foliar-applied N was recovered than N broadcast at planting, due partly to pre-emergence losses of nitrate in 1986. It is suggested that late applications of N was foliar sprays can be of benefit to crops with a long growing season and reduce environmental losses of N.     

沸石-核桃壳曝气生物滤池去除废水中氨氮的研究

采用核桃壳和沸石组合作为曝气生物滤池填料,处理废水中的NH_4~+-N。试验期间,每天定时监测曝气生物滤池进水和出水的pH、溶解氧、COD、NH_4~+-N、亚硝酸盐氮和硝酸盐氮等水质指标。考察了核桃壳-沸石曝气生物滤池的脱氮性能,研究了水力负荷和气水比对曝气生物滤池去除NH_4~+-N效率的影响。此外,研究了曝气生物滤池的沿程特性。试验结果表明,核桃壳和沸石是可取的曝气生物滤池填料,具有较好的硝化能力,能有效地去除污染物。最佳水力负荷为0.04 m/h,最佳气水比为6∶1,在此条件下,NH_4~+-N去除率保持在80%以上。填料层底部向上25~55 cm段为NH_4~+-N去除高效段。     

Effect of a new nitrification inhibitor (wax coated calcium carbide) on transformations and recovery of fertilizer nitrogen by irrigated wheat

The effectiveness of wax coated calcium carbide to provide a slow release of acetylene to inhibit nitrification and denitrification in soil was evaluated in a field experiment with irrigated wheat (cv. Condor) grown on a red brown earth in the Goulburn-Murray Irrigation Region. The effect of the inhibitor treatments on biomass and grain yield was determined in 25 m × 3 m plots, and the effect on recovery, in the plant-soil system, of urea-N applied at sowing was determined in 0.3 m × 0.3 m microplots using a¹⁵N balance technique. The inhibitor limited ammonium oxidation, prevented nitrogen loss by denitrification for 75 days, increased N accumulation by the wheat plants, increased grain N and resulted in a 46% greater recovery of applied nitrogen in the plant-soil system at harvest. However, the inhibitor treatment did not increase grain yield because of waterlogging at the end of tillering and during stem elongation.     

The content and yield of six elements in four grasses as affected by nitrogen application and interval between harvests

Effects of three levels of applied nitrogen and 4- and 8-week intervals between cuts on the nitrogen, phosphorus, potassium, calcium, magnesium and sodium content and yield of four grasses grown in field swards were studied in three full harvest years. Concentrations of elements in herbage lower than those required by some classes of livestock were found as follows: in the case of phosphorus, where high yields of grass were obtained without any very recent application of phosphorus; in the case of calcium, mainly at harvests in late April/early May; in the case of magnesium, in most of the grass harvested in April, May, June and July; in the case of sodium, where no nitrogen or the intermediate level was applied, except at the October/November harvests; in the case of nitrogen, at harvests in May and July with the 8-week interval and no applied N. Suggestions are made as to ways of raising the concentrations where necessary. The concentration of potassium in herbage was greatly in excess of animal requirements; possible ways of economizing on potassium application are considered. Applied nitrogen (as Nitro-chalk) greatly reduced extractable soil potassium, reduced soil magnesium, and had little or no effect on soil calcium, sodium or pH.