Ammonia volatilization losses from fertilizers applied to acid soil in the field

Losses of ammonia by volatilization from ammonium sulphate and urea applied to soil were studied in field conditions.Losses from ammonium sulphate generally were not large; ammonia volatilization is thus unlikely to be an important pathway of nitrogen loss from cropped soils, and does not explain the low responses to nitrogen fertilizer of wheat grown in the higher rainfall cropping areas of South-Eastern Australia.Losses of nitrogen from ammonium sulphate were not greatly affected by meteorological variables, rate of application, water applicaton or incorporation into soil.The above variables all affected losses of nitrogen from urea, by influencing the rates of solution and hydrolysis of urea, and volatilization of ammonia. Losses ranged from 4 to 50% of the applied urea-nitrogen. Losses of urea-nitrogen were large when evaporation rates were high, and large variations occurred in the rates at which urea could be hydrolyzed.Extrapolation of the results to grazing conditions suggests that ammonia volatilization may result in large losses of nitrogen from short pastures in dry conditions.     

Leaching losses of urea-N applied to permeable soils under lowland rice

Application of 120 kg urea-N ha^–1 to lowland rice grown in a highly percolating soil in 10 equal split doses at weekly intervals rather than in 3 equal split doses at 7, 21 and 42 days after transplanting did not significantly increase rice grain yield and N uptake. Results suggest that leaching losses of N were not substantial. In lysimeters planted with rice, leaching losses of N as urea, NH ₄ ⁺ , and NO ₃ ^- beyond 30 cm depth of a sandy loam soil for 60 days were about 6% of the total urea-N and 3% of the total ammonium sulphate-N applied in three equal split doses. Application of urea even in a single dose at transplanting did not result in more N leaching losses (13%) compared to those observed from potassium nitrate (38%) applied in three split doses. Nitrogen contained in potassium nitrate was readily leached during the first week of its application. More N was lost from the first dose of N applied at transplanting than from the second or third dose. Data pertaining to yield, N uptake and per cent N recovery by rice revealed that the performance of different fertilizer treatments was inversely related to susceptibility of N to leaching.     

Comparative studies on the usefulness of ammonium sulphate and urea as fertilizers for lowland rice

In a pot experiment it was established that NH₄ volatilization losses were larger with urea than with ammonium sulphate used as a basal fertilizer for lowland rice. The difference arose from the pH-increasing effect of urea in the floodwater. This rise in pH promoted the growth of algae which in turn were responsible for large diurnal fluctuations in the pH of the floodwater thus enhancing the loss of NH₃ during daytime. Ammonium sulphate lowered the pH of the water which suppressed the growth of algae.Once the rice canopy had closed, the algal population declined and the diurnal pH fluctuations largely disappeared. Urea as a topdressing was found to be less liable to give rise to NH₃ volatilization than when added as basal dressing. The highest N recovery was obtained with ammonium sulphate used as basal dressing and urea as topdressing. Working a basal dressing into the soil improves the fertilizer-N recovery of urea-N, but not of ammonium sulphate-N, the latter being already high without soil incorporation.     

Nitrogen loss from ammonium bicarbonate and urea fertilizers applied to flooded rice

Total nitrogen loss and ammonia volatilization from applications of ammonium bicarbonate and urea to flooded rice (Oryza sativa L.) grown on an acidic lacustrine clay in China were measured by¹⁵N balance and micrometeorological methods. Attempts were also made to reduce nitrogen loss by using different methods of applying the fertilizers.Ammonia volatilization from ammonium bicarbonate was greater than that from urea (18.2% and 8.8%, respectively, of the applied N). The total loss of ammonia from urea in this study was less than the losses observed in similar studies elsewhere. This was presumably because of the low incident radiation and low floodwater pHs in this experiment.Denitrification losses, calculated as the difference between total nitrogen loss and ammonia loss, were 42.2% and 39.3%, respectively, for ammonium bicarbonate and urea, and thus were more important than ammonia losses from both types of fertilizer.The different management treatments studied had an appreciable effect on ammonia flux densities but did not reduce the overall loss as measured by¹⁵N-balance.     

Nitrification and nitrate movement from ammonium sulphate and urea in sandy soils as affected by their previous applications

Two successive applications of urea and ammonium sulphate (AS) at varying intervals were given in two soils, one of which was salt affected. The nitrification and nitrate leaching after both the applications of fertilizers was studied. The nitrification of first application of AS was faster than urea on both soils. However, the nitrification rate of both fertilizers was slow in salt effected soil. The same trend of results was observed with second application of fertilizers. However, the nitrification of second application given within 6 weeks of the first application proceeded at a much faster rate than that of the first application. The amount of NO ₃ ^- that moved down with periodic water application was related with nitrification rate and the amount of fertilizer nitrified at the time of water application.     

Control of gaseous nitrogen losses from urea applied to flooded rice soils

This paper reports field experiments designed to determine whether the two main processes responsible for nitrogen (N) loss from flooded rice (ammonia volatilization and denitrification) are independent or interdependent, and glasshouse studies which investigated the effect of soil characteristics on gaseous nitrogen loss.In the first field experiment ammonia (NH₃) loss from the floodwater was controlled using algicides, biocides, frequent pH adjustment, shade or cetyl alcohol, and the effect of these treatments on total N loss and denitrification was determined. Most treatments reduced NH₃ loss through their effects on algal growth and floodwater pH. Total gaseous N loss (54% to 35%) and NH₃ loss (20% to 1.2%) were affected similarly by individual treatments, indicating that the amount lost by denitrification was not substantially changed by any of the treatments.In a subsequent field experiment NH₃ and total N loss were again affected similarly by the treatments, but denitrification losses were very low. In control treatments with different rates of urea application, NH₃ and total N loss were each a constant proportion of the urea applied (NH₃ loss was 17% and total N loss was 24%). These results indicate that techniques which reduce NH₃ loss can be expected to reduce total gaseous N loss.The glasshouse experiment showed that gaseous N losses could be reduced by draining off the floodwater, and incorporating the urea into the 0–0.05 m soil layer before reflooding. Even with this method, losses varied widely (6–27%); losses were least from a cracking clay and greatest from a coarse sand which allowed the greatest mobility of the applied N. Incorporation of applied urea can therefore be expected to prevent losses more successfully from clay soils with high ammonium retention capacity.     

氯化钾-硫酸铵法生产硫酸钾精制研究

为了解决氯化钾—硫酸铵法生产的硫酸钾产品纯度低的问题，对硫酸钾精制过程进行了研究。在理论指导下，根据正交设计试验结果，通过极差和方差分析，确定结晶温度、反应时间、配料比都显著影响硫酸钾的收率。同时得到精制过程的优化工艺条件；结晶温度40℃，反应时间90min,氯化钾与硫酸钾的配料质量比为0.15。实验结果为：硫酸钾的单次收率达到85.26%，循环总收率接近100%。     

硫酸铵与氯化钾生产硫酸钾的研究

研究了氨法脱硫副产的硫酸铵溶液直接与氯化钾进行复分解反应生成K2SO4结晶的工艺参数.离心分离K2SO4结晶,经干燥后制得合格的农用化肥硫酸钾产品.试验表明：反应时间3h、反应温度30℃、L/G为1.2,KCl与（NH4） S04质量比1.10条件下,采用硫酸铵与KCl定量配比投料能生产出硫酸钾合格品.     

用天然石膏制备硫酸铵和氯化钙的工艺研究

以天然石膏和碳酸氢铵为原料进行复分解反应制备硫酸铵,副产碳酸钙粗品。考察了反应温度、反应时间、配料比、液固比等因素对硫酸钙转化率的影响,通过正交实验确定了复分解反应的最佳工艺条件。探讨副产物碳酸钙的回收利用方法,用盐酸处理碳酸钙粗品制备氯化钙,研究确定了工艺条件。整个生产过程无废渣排放,工艺简单清洁。通过本方法,可将天然石膏转化为具有更高价值的硫酸铵和氯化钙,研制的产品质量达到有关标准,应用前景广阔。     

Characterization of products of interaction between kaolin ore and ammonium sulphate

The reaction products resulting from the interaction between kaolin ore and ammonium sulphate depend on molar ratios between reactants, reaction temperature and time of interaction. The reaction products were characterized by means of XRD. They were composed of silica, unreacted kaolin ore, traces of iron, magnesium, calcium, titanium and NH₄Al(SO₄)₂ and (NH₄)₃Al(SO₄)₃. The last compound was produced alone at 553 K, whereas mixtures of them were produced between 553 and 823 K after a short time of interaction (0.5 h). On other hand the former compound was produced alone after longer heating (c. 2 h). At 823 K, a mixture composed of Al₂(SO₄) and NH₄Al(SO₄)₂ was identified after 0.5 h, whereas anhydrous aluminium sulphate was detected alone after heating the reaction mixture for 2 h. The transformation of (NH₄)₃Al(SO₄)₃ into NH₄Al(SO₄)₃ and alumina leads to a decrease in the percentages of extracted alumina from kaolin ore at relatively higher temperatures and/or longer heating of reaction mixtures. The investigation was also devoted to establishing the possible reactions which lead to the formation of Fe₂O₃, MgO, CaO and TiO₂ as soluble salts together with aluminium compounds. The percentages of their extraction are low compared with the original quantities found in kaolin ore. From the obtained results, both Al₂(SO₄)₃ and NH₄Al(SO₄)₂ can be prepared from local kaolin with a reasonable degree of purity which makes it possible to produce them for use for different industrial and pharmaceutical purposes.     

Nitrogen losses from fertilizers applied to maize, wheat and rice in the North China Plain

Ammonia volatilization, denitrification loss and total nitrogen (N) loss (unaccounted-for N) have been investigated from N fertilizer applied to a calcareous sandy loam fluvo-aquic soil at Fengqiu in the North China Plain. Ammonia volatilization was measured by the micrometeorological mass balance method, denitrification by the acetylene inhibition – soil core incubation technique, and total N loss by ¹⁵N-balance technique. Ammonia loss was an important pathway of N loss from N fertilizer applied to rice (30–39% of the applied N) and maize (11–48%), but less so for wheat (1–20%). The amounts of unaccounted-for fertilizer N were in the order of rice > maize > wheat. Deep placement greatly reduced ammonia volatilization and total N loss. Temperature, wind speed, and solar radiation (particular for rice), and source of N fertilizer also affect extent and pattern of ammonia loss. Denitrification (its major gas products are N₂ and N₂O) usually was not a significant pathway of N loss from N fertilizer applied to maize and wheat. The amount of N₂O emission (N₂O is an intermediate product from both nitrification and denitrification) was comparable to denitrification loss for maize and wheat, and it was not significant in the economy of fertilizer N in agronomical terms, but it is of great concern for the environment.     

Effect of soil clay mineralogy on the efficiency of ammonium sulfate in flooded rice

The effect of soil clay mineralogy on the efficiency of (NH₄)₂SO₄ in flooded rice was investigated in a greenhouse pot trial with four clayey soils of diverse clay mineralogies (x-ray amorphous, montmorillonite, vermiculite, beidellite). KCl (75 kg K ha^–1) and triple superphosphate (25 kg P ha^–1) were incorporated in the soil with and without (NH₄)₂SO₄ (100 kg N ha^–1) before transplanting 1-week-old IR-36 rice seedlings which were then grown to maturity under flooded conditions. Efficiency of (NH₄)₂SO₄ was inferred from the response of agronomic characteristics such as tiller number, height, grain and straw yields to NH₄ fertilization.The results showed greatest efficiency of (NH₄)₂SO₄ on the x-ray amorphous soil, followed by montmorillonitic soil; efficiency was much lower on the vermiculitic and negligible on the beidellitic soil.Soil clay mineralogy may be an important factor in the reduced efficiency of NH₄ (or NH₄-forming) fertilizers in certain rice soils.     

Balance sheet of15N labelled urea applied to rice in three Australian vertisols differing in soil organic carbon

A glasshouse experiment was conducted to study the balance sheet of¹⁵N labelled urea at three rates (zero, 31.48 and 62.97 mmol N pot^–1) applied to rice under flooded conditions with two moisture regimes (continuous and alternate flooding) using three Australian vertisols differing in organic carbon level. Walkley-Black organic carbon values for the three soils were 0.65, 2.13 and 3.76 for the low carbon (LC), medium carbon (MC) and high carbon (HC) soils respectively.Rice dry weight and nitrogen uptake was significantly affected by N fertilizer rates, water regimes and soils. Alternate flooding gave much lower dry weight and nitrogen uptake than continuous flooding and the LC soil gave lower dry weight and nitrogen uptake than for the MC and HC soils.Recovery of¹⁵N labelled urea fertilizer in the rice plant was low (15.4 to 38.4%) and the¹⁵N urea not accounted for in the plant or soil and presumed lost was high (36.2 to 76.0%). Recovery was lower and loss higher under alternate flooding and for the LC soil. There was no effect of fertilizer rate. The results obtained stress the need for careful management to reduce losses of nitrogen fertilizer, particularly for soils low in organic carbon.     

Fate of nitrogen applied in different fertilizers to the surface of a calcareous soil in Syria

¹⁵N-labelled ammonium sulphate or¹⁵N-labelled urea were each applied in solutionat a rate of 30 kg N ha^-1 to the surface of 20soil cores (52 mm internal diameter × 100 mm deep)located on a field experiment at the ICARDA station,Tel Hadya, Syria. Recovery of ¹⁵N-label in theammonium, nitrate, organic and/or urea-N pools in thesoil was measured on days 0, 1, 2, 5 and 13 afterapplication. Total recovery of ¹⁵N was initially100%, but by day 13 after application it had declinedto 51% with urea and 73% with ammonium sulphate.Ammonium nitrate labelled either as ammonium or asnitrate was also applied to the soil surface of 8other cores at the same time. ¹⁵N recovery in thefour soil N pools was measured only on day 12 afterapplication. Total recovery of ¹⁵N-label was 75%with labelled ammonium and 57% with labelled nitrate.Volatilization of ammonia from this calcareous soil(pH 8.1) is one probable mechanism of N loss fromammonium and urea fertilizers: with nitrate bothleaching beyond the base of the core (i.e. 100 mm) and denitrification were responsible for Nlosses. These large losses of N immediately afterapplication have implications for fertilizermanagement practices.     

Nitrogen leaching and uptake from calcium cyanamide in comparison to urea and calcium ammonium nitrate in an ultisol from the humid tropics

Leaching loss of N applied as calcium cyanamide (CaCN₂ — 19% N), urea and calcium ammonium nitrate (CAN — 26% N) to a coarse textured, kaolinitic ultisol profile was studied in the laboratory using undisturbed soil columns. The soil columns were leached with an amount of water equivalent to the annual rainfall of the sampling site (2420mm) using a rainfall simulator over a period of 42 days. The leachability of the three N fertilizers differed greatly and followed the order of CAN > urea > CaCN₂. Most of the N lost through leaching was in NO₃ form. Calcium cyanamide lost only 3% of applied N. Breakdown of CaCN₂ to NH₄ was incomplete (64%) and nitrification in the soil was inhibited resulting in negligible leaching loss. Nitrogen retained in the soil columns after the leaching cycle was mainly in ammoniacal form irrespective of source of N used.Effectiveness of CaCN₂ as a N source was also studied in a greenhouse experiment with maize (Zea mays) and upland rice (Oryza sativa) as testing crops. Calcium cyanamide applied one week before sowing of crops was as effective as CAN and urea under conditions of no N leaching. When applied at the time of planting and two or more weeks before planting gave lower dry matter yields and N uptake than CAN and urea.IITA Journal Paper no. 351     

Ammonia volatilization from a flooded rice field fertilized with amended urea materials

The extent of ammonia volatilization from prilled urea, urea supergranule and urea amended with neem seed cake, shell-lac and dicyandiamide was studied in a field experiment on flooded rice. The ammonia loss was measured by the closed acid trap method. The collected ammonia was highest from unamended prilled urea, accounting for 19 to 20 per cent of the applied N in 1983 and 20 to 24 per cent of the applied N in 1984. Coating of urea prills was either coaltar soaked neem seed cake or shell-lac was more effective than coating with dicyandiamide in reducing ammonia loss. Deep placement of urea as a supergranule was the most effective method of reducing ammonia volatilization. A diurnal variation in the pH and temperature of floodwater was observed. The quantity of ammonia collected in the acid trap was closely related to ammoniacal-N concentration and pH of the floodwater.     

Extraction of zinc from ammoniacal/ammonium sulphate solutions by LIX 54

The extraction of zinc from ammoniacal/ammonium sulphate aqueous media using LIX 54 has been studied. The metal extraction rate has been examined and also the effect of temperature on the extraction of zinc (ΔH° = −8·8 kJ mol⁻¹). The effect of the aqueous pH, and therefore zinc ammine complex formation, on the extraction of zinc was studied. Stripping of the metal from loaded organic phases was carried out at various rates, temperatures (ΔH° = 3·2 kJ mol⁻¹) and sulphuric acid concentrations. The results obtained were compared with others obtained from the literature wherein different extractants were used. © 1998 SCI.     

Relative susceptibility of conventional and experimental nitrogen sources to ammonia loss from flooded rice fields

Urea, the most common N source in Asia, is prone to high loss as ammonia when applied to tropical flooded rice (Oryza sativa L.). Chemical or physical modifications of urea could offer potential in reducing ammonia loss. Two field studies were conducted to identify conventional and experimental N-containing sources loss prone to ammonia less than prilled urea. Relative susceptibility to ammonia loss was inferred from equilibrium ammonia vapor pressure, pNH₃. For the sources studied, ammonia formation and presumably loss were least for guanylurea sulfate (GUS) and sulfur-coated urea (SCU). The slow mineralization and acidifying effect of GUS resulted in negligible ammonia concentration in the floodwater. Amendment of urea with either 5 or 10% paraformaldehyde (ureaform) reduced pNH₃, but never by more than 55%. Coating urea with phosphate rock tended to be less effective than amendment with paraformaldehyde in reducing pNH₃. There was no significant difference in the pNH₃, and presumably ammonia loss, for urea phosphate (17-44-0), urea-urea phosphate (34-17-0), and urea. About 3 days after fertilization, the floodwater pH tended to become higher with NP sources than with urea. This elevation in pH was apparently due to the stimulation of algal photosynthetic activity by added P, and it may explain the failure of a phosphoric acid amendment to urea (urea phosphate) in reducing pNH₃. Ammonia disappearance from broadcast diammonium phosphate (DAP) and ammonium phosphate sulfate (16-20-0) was complete within 3 days after N application, whereas ammonia remained in floodwater for up to 7 days following broadcast application of urea and ammonium sulfate.     

Efficiency of urea and ammonium sulfate for wetland rice grown on an acid sulfate soil as affected by rate and time of application

A pot experiment was conducted in a greenhouse to assess the effect of rate and time of N application on yield and N uptake of wetland rice grown on a Rangsit acid sulfate soil (Sulfic Tropaquepts). Response of rice at N rates of 800, 1600 and 2400 mg N/pot (5 kg of soil) was compared between urea and ammonium sulfate when applied at two times: (i) full-rate basal at transplanting and (ii) one half at transplanting and one half at the PI stage. In addition, labelled¹⁵N sources were applied either at transplanting or at the PI stage to determine the nitrogen balance sheet in the soil/plant system.No significant difference in grain and straw yields between urea and ammonium sulfate at low rate was observed. At the higher N rates, urea produced higher yields than did ammonium sulfate regardless of timing. The highest yields were obtained when urea at the high N rate was applied either in a single dose or a split dose while lowest yields were observed particularly when ammonium sulfate at the same rate was applied. Split application of N fertilizer was shown to be no better than a single basal application. The occurrence of nutritional disorder, a symptom likely reflected by high concentration of Fe (II) in combination with soluble Al, was induced with high rate of ammonium sulfate.In terms of fertilizer N recovery by using¹⁵N-labelling, ammonium sulfate was more efficient than urea when both were applied at transplanting. In contrast, application at the PI stage resulted in higher utilization of urea than of ammonium sulfate. The recovery of labelled N in the soil was higher with urea than with ammonium sulfate when the two sources were applied at transplanting, while the opposite result was obtained when the same fertilizers were applied at the PI stage. The losses from urea and ammonium sulfate were not different when these fertilizers were applied at transplanting but loss from urea was higher than that from ammonium sulfate when both were applied at the PI stage.     

Relative ammonia loss from urea-based fertilizers applied to rice under different hydrological situations

Relative ammonia volatilization loss from prilled urea, urea supergranule (USG), neem cake-coated urea (NCU), rock phosphate-coated urea (RPCU), gypsum-coated urea (GCU), and prilled urea supplemented with dhaincha (Sesbania aculeata) green manure (Dh + PU) was measured in the fields under different hydrological situations of rice growing. Ammoniacal-N and pH of flood water were less with point placement of USG and Dh + PU treatments than with single basal broadcast applications of urea-based fertilizers. Ammonia collected with an acid trap in an enclosed chamber ranged from 1.47–3.07, 0.24–3.74, 0.80–3.50 and 0.50–1.20% of the applied N in upland, alternate wetting and drying, shallow submergence and intermediate deep water situations, respectively. The collected ammonia was less with point placement of USG at 5 cm depth in all situations and with Dh + PU treatment in shallow submergence than with other sources of N. Single basal broadcast applications of RPCU or NCU resulted in relatively higher loss. The loss from top-dressed urea was less than that from basally applied urea because of larger crop canopy at later stages of crop growth.