Controlling ammonia volatilization from urea surface applied to sugar beet on a calcareous soil

Abstract

The extent of ammonia (NH₃) volatilization from surface‐applied urea to sugar beet and effects of NBPT [N‐(n‐butyl) thiophosphoric triamide] PG (phosphogypsum), PR (by‐product‐pyrite) and KCl (potassium chloride) on NH₃ volatilization, nitrogen (N) content of leaf blades and petioles, sugar, amine N, and refined sugar contents, and root and refined sugar yields were determined in the field. Total NH₃ loss varied from 7.0% to 23.6% depending on the compounds incorporated with urea and rate of addition. With respect to unamended urea, 540 kg KCl/ha, 1000 kg phosphogypsum/ha, and 1000 kg pyrite/ha increased NH₃ loss by 86.7%, 40.1%, and 36.2%, respectively, but the other treatments decreased the loss. The highest reduction of NH₃ loss was found with 0.5% of NBPT by 44.5%. The NBPT, KCl, and PG treatments increased both root and refined sugar yields compared with urea alone. The highest refined sugar yield and lowest NH₃ volatilization loss was obtained with 0.5 % of NBPT treatment.     

Effects of plant material on ammonia volatilization from simulated livestock urine applied to soil

Summary The volatilization of ammonia from simulated urine applied to small columns of soil was reduced by the presence of ryegrass growing in the soil. The ryegrass had been sown 18 weeks previously and had been cut on seven occasions to a height of 5–6 cm with the cut herbage removed. Cumulative volatilization over 8 days amounted to 39% of the urinary N from bare soil, and 23% in the presence of the ryegrass. In contrast, the volatilization of ammonia was increased by dead leaf litter placed on the soil surface, apparently due to the increase in surface area for urease activity and volatilization. Differences in the C:N ratio of the leaf litter over the range 13:1–29:1 had little effect on the extent of ammonia volatilization. When living ryegrass and dead leaf litter were examined together, the reduction in volatilization due to the ryegrass was the dominant effect.     

Effects of some environmental factors on ammonia volatilization from simulated livestock urine applied to soil

Summary The proportion of the N that was volatilized as ammonia during 8 days, following the application of simulated livestock urine to soil, increased from 25 to 38% as the temperature of incubation was increased from 4° to 20°C in a system with a continuous flow of air at 70% relative humidity. However, volatilization was reduced if the application was followed by simulated rain; the reduction was greater as the amount of rain increased (up to at least 16 mm) and became less with an increasing length of time (up to 2–3 days) after the application of the urine. The effects of the soil water content before application of the urine, and of the relative humidity of the air, were generally small but volatilization was reduced by a combination of air-dry soil with a low relative humidity. Volatilization was slight (7%) when the flow of air was restricted to 0.5 h in every 12 h but, with an air flow for 12 h in every 24 h, the volatilization was much closer to that with a continuous flow for the whole 8-day period. When cool or dry conditions were imposed for 8 days and then more favourable conditions were instituted for a second period of 8 days, there was a substantial increase in volatilization following the change.     

改性尿素施用对氨挥发量及无机氮变化的影响

采用室内土壤培养和玉米幼苗盆栽试验的方法,研究了改性尿素施用后的氨挥发量及其对土壤无机氮和pH值的影响。结果表明:(1)表施改性尿素比表施普通尿素的氨挥发量显著减少,从而降低氮素的损失;在一定范围内,土壤含水量越大,氨挥发量越低。(2)硝化抑制剂双氰胺(DCD)能够抑制土壤硝化作用,使NH+4-N能较长时间存在土壤中,从而减少NO-3-N的损失;在一定范围内,DCD施用浓度越大,抑制效果越好。(3)土壤pH值与铵态氮呈极显著指数正相关,与硝态氮呈极显著线性负相关,与无机氮呈多项式相关。因此,改性尿素能够显著减少氨挥发量,抑制土壤硝化作用,从而降低尿素的氮素损失。     

A model of ammonia volatilization from applied urea. IV. Effect of method of urea application

Equations are given for calculating the initial distribution when a solute is (a) applied at the surface (b) placed below the surface and (c) mixed uniformly in a given depth of top soil. These equations are plugged into a predictive model developed by the authors (Rachhpal-Singh & Nye, 1986a) to compare the concentration profiles of ammoniacal-nitrogen and soil pH, and ammonia volatilization losses under the three methods of urea application. Placement of urea gave smaller ammonia losses than uniform mixing in the same depth of soil, which in turn gave smaller losses than surface application. Half-time for ammonia volatilization was about 6 days irrespective of the method and depth of urea application. Concentration profiles of ammoniacal-nitrogen and soil pH were more affected by variation in the depth of placement than by depth of mixing. The experimental ammonia volatilization losses and the concentration profiles of ammoniacal-nitrogen and soil pH agreed very well with those predicted by the model.     

棉酚渣对尿素水解及土壤氨挥发的影响

采用棉酚渣、尿素和土壤混合培养,测定剩余尿素量及氨气吸收量的方法,探究棉酚渣对尿素水解及土壤氨挥发的影响。结果表明,随尿素中棉酚渣的用量增加,尿素残余量增加,氨气检测量减少。与对照相比,培养时间为4 d时尿素残留差异率达78.81%,氨气挥发抑制率可达80.40%。土壤含水率变化对脲酶和产生脲酶的微生物的活性有较大影响,在活性高时,棉酚渣对尿素水解和氨挥发的抑制作用更加明显。随着培养温度的升高,尿素水解增加,氨挥发迅速增加。35℃时,棉酚渣对尿素水解的抑制效果最好,尿素残留差异率达79.72%,30℃时,棉酚渣对氨气挥发抑制效果最好,氨挥发抑制率达55.34%。上述结果表明,棉酚渣对尿素水解及土壤氨挥发具有较强的抑制作用,具有推广应用的潜力。     

红壤不同含水量对尿素氨挥发的影响

根据第四纪红壤水分特征设计160、200、240、280、320、360g/kg6个土壤含水量处理,通过温室模拟,研究了红壤不同含水量对尿素氨挥发的影响。结果表明,等量尿素施入红壤后,氨挥发通量与土壤含水量之间无显著相关性,而高含水量(280、320、360g/kg)处理氨挥发通量峰值较低含水量(160、200g/kg)处理提前10天。氨挥发过程可分为快速-慢速2个阶段,氨累积挥发量(y)与对应时间(t)符合Elovish动力学方程(y=a blnt)。第1～10天,氨挥发累积量随红壤含水量的增加而递增;第11天后,以含水量为240g/kg处理的氨挥发累积N量最低。试验期间,氨挥发累积总N量,以含水量240g/kg时最低(0.90gN),含水量320g/kg时最高(1.16gN),分别占尿素施入N量的9.0%和11.6%。     

A model of ammonia volatilization from applied urea. II. Experimental testing

Experimental methods for the measurement of the transfer coefficient for ammonia volatilization from the soil surface to the atmosphere, the gaseous diffusion impedance factor in soil, and other parameters required by the predictive model are described. Following surface application of urea to soil columns, the measured concentration profiles of urea, ammoniacal-nitrogen and soil pH, and the losses of ammonia by volatilization, were compared with the model predictions. The very good agreement between the measured and the predicted results suggested that all important processes have been accounted for in the model.     

太湖水稻土麦季尿素氨挥发损失

Ammonia volatilization losses from urea applied as a basal fertilizer and a top dressing at tillering stage in a wheat field of Taihu Region, China, were measured with a micrometeorological technique. Urea as fertilizer was surface broadcast at 81 (low N) and 135 (high N) kg N ha-1 as basal at the 3-leaf stage of the wheat seedling on December 2002, and 54 (low N) and 90 (high N) kg N ha-1 as top dressing on February 2003. Ammonia volatilization losses occurred mainly in the first week after applying N fertilizer and mainly during the period after basal fertilizer application, which accounted for more than 80% of the total ammonia volatilization over the entire wheat growth period. Regression analysis showed that ammonia volatilization was affected mainly by pH and NH4^ -N concentration of the surface soil and air temperature.Ammonia volatilization flux was significantly correlated with pH and NH4^ -N concentration of the surface soil and with daily air average temperature and highest temperature. Thus, application of urea N fertilizer to wheat should consider the characteristics of ammonia volatilization in different periods of N application so as to reduce ammonia losses.     

Effect of urease inhibitors on urea hydrolysis and ammonia volatilization

Summary Two laboratory incubation experiments were conducted to study the effects of the urease inhibitors hydroquinone (HQ), phenyl phosphorodiamidate (PPDA), and N-(n-butyl) thiophosphoric triamide (NBPT) in retarding the hydrolysis of urea, in the evolution of mineral N, and in reducing NH₃ loss through volatilization, under aerobic and waterlogged conditions, both at 25°C. NBPT generally exceeded PPDA and HQ in the ability to delay urea hydrolysis and NH _inf4 ^sup+ accumulation under aerobic conditions, whereas PPDA retarded these activities more effectively under anaerobic conditions. HQ was less effective than the other two urease inhibitors. Under aerobic conditions, 20% of the applied urea was lost through NH₃ volatilization after 5 days in the system without an inhibitor. With the addition of HQ and PPDA, the volatilization was delayed by 1 day but not eliminated. NBPT effectively decreased the NH₃ loss, from 20 to 3% of the applied urea. A more severe N loss (40%) occurred in the waterlogged system. HQ had little effect on NH₃ volatilization. PPDA decreased the NH₃ loss from 40 to less than 20% of the applied urea. The effectiveness of NBPT decreased under anaerobic conditions. It was concluded that urease inhibitors can reduce NH₃ volatilization following the application of urea. However, environmental conditions might have an important influence on the effectiveness of these inhibitors.     

A model of ammonia volatilization from applied urea. III. Sensitivity analysis, mechanisms, and applications

A sensitivity analysis of the model described in Part I showed that the proportion of N lost as ammonia from surface applied urea is very sensitive to the initial pH of the soil, its pH buffer capacity, the rate of urea application, and the soil urease activity. Under the conditions tested, the diffusion of bicarbonate ion to the soil surface, to neutralize the acid generated when NH₄⁺ is volatilized as NH₃, appeared to be the main process controlling the rate of ammonia volatilization. The amount of ammonia volatilized was not very sensitive to the value of the transfer coefficient between the soil surface and the atmosphere, nor to the soil moisture status if this was around field capacity. Adsorption of ammoniacal-nitrogen was less important than the soil pH buffer capacity in influencing the ammonia volatilization. Further applications and extensions of the model are discussed.     

A model of ammonia volatilization from applied urea. I. Development of the model

Urea application to soil raises the pH and ammonium concentration, thus providing ideal conditions for ammonia volatilization. A mechanistic model is presented, which combines the process of ammonia volatilization with the simultaneous transformation and movement of urea and its products in soil, for predicting the concentration profiles of urea, ammoniacal-nitrogen and soil pH, and ammonia losses, following application of urea. The model consists of continuity equations describing the diffusion and reaction of urea, ammoniacal-nitrogen and soil base; it takes into account the volatilization of ammonia and the concurrent acidification of the soil surface; and considers a variable P_Co2 profile due to soil respiration and urea hydrolysis. The derivation of the continuity equations and their boundary conditions, calculations of ammonia volatilization, and appropriate methods for numerical solutions are described.     

Effect of blending urea with pyrite or coating urea with polymer on ammonia volatilization loss from surface-applied prilled urea

Laboratory studies on a sandy clay loam (Typic Ustochrept) alkaline soil showed that NH₃ volatilization loss from surface-applied prilled urea during an 8-dya incubation under aerobic conditions was 27.5% of applied N (400 kg N ha^-1) and was reduced to 8.9% when the urea was blended physically with pyrite in a 1:2 ratio; under anaerobic conditions the values for urea and pyrite-urea were 19.3 and 16.9%, respectively. Other treatments tested were urea-gypsum, neemcake-coated urea and polymer-coated urea. A 6% polymer coating showed the least NH₃ volatilization under anaerobic conditions and was next best to pyrite-urea under aerobic conditions. A 3% polymer coating was slightly inferior to the 6% coating. Urea-gypsum and neemcake-coated urea did not differ very much from urea alone under anaerobic conditions, but under aerobic conditions neemcake-urea showed a significantly lower total NH₃ loss compared to prilled urea alone and urea-gypsum.     

Effect of ammonium sulfate pretreatment on ammonia volatilization after urea fertilization

Abstract

Urea applications to soil are subject to loss by ammonia (NH₃) volatilization, unless incorporated. It has been proposed that this loss can be reduced by stimulating populations of soil nitrifiers by an ammonium sulfate [(NH₄)₂SO₄] pretreatment two to four weeks before urea application. The objective of this laboratory trial was to evaluate this concept with five diverse soils, two North American Mollisols and three South American Oxisols. The soils were incubated untreated for two weeks, followed by pretreatment with 0 or 5 kg nitrogen (N) ha^‐1 as (NH₄)₂SO₄, on a soil surface area basis. After another two weeks of incubation, the soils were treated with the equivalent of 0 or 50 kg N ha^‐1 as urea. Ammonia loss was estimated after trapping into phosphoric acid (H₃PO₄). Ammonium sulfate pretreatment reduced NH₃ loss with the two Mollisols and a sandy Oxisol and increased the recovery of the urea application as mineral [ammonium (NH₄ ⁺) + nitrate (NO₃ ^‐)] N in these soils. Little NH₃ loss was detected from the two clay Oxisols, and (NH₄)₂SO₄pretreatment did not influence NH₃ loss or recovery of urea as mineral N. An example of a cropping system where this concept may have utility is discussed.     

Ammonia volatilization from ammonium sulphate,ammonium nitrate,and urea surface applied to winter wheat on a calcareous soil

Abstract

Ammonia (NH₃) volatilization losses from surface‐applied ammonium sulphate (AS), ammonium nitrate (AN), and urea to winter wheat and the effects of the NBPT [N‐(n‐butyl) thiophosphoric triamide], PG (Phospho‐gypsum), and PR (byproduct‐Pyrite) were determined in a field experiment. Effects on grain yield and protein content of the grain were also measured. Total NH₃ losses from AS, AN, and urea varied from 13.6–19.5%, 4.4–6.4%, and 3.9–12.0% depending on the compounds and their levels added to nitrogen (N) fertilizers, respectively. The compounds added to AS and AN increased NH₃‐N losses with respect to unamended fertilizers (control). On the other hand, while urea treatments with two tons of PG/ha increased NH₃ losses, the other compounds decreased the losses. The highest reductions of NH₃ loss were observed with NBPT 0.50% and NBPT 0.25% by 63.4% and 52.8%, respectively. Although the effect of nitrogeneous fertilizers on total N losses and protein content of wheat grain was found statistically significant (p<0.01), as the compounds applied with N fertilizers have had no significant effect. Also, a negative and highly significant correlation (r = ‐0.69???) was found between total N loss and protein content of the grain.     

Effect of air flow rate,lime amendments,and chemical soil properties on the volatilization of ammonia from fertilizers applied to sandy soils

NH₃ volatilization from surface-applied urea, diammonium phosphate (DAP), and calcium ammonium nitrate (CAN) was measured with chambers through which air was drawn continuously. Two sandy soils and two sandy loam soils, which had been treated with and without time for the last 25 years, were used for the experiments. The accumulated NH₃ loss from CAN applied to an unlimed sandy soil was linearly related to time. For the other treatments the accumulated loss was exponentially related to time. The NH₃ loss was exponentially related to the maximum soil pH of the fertilizer-amended soil, and was inversely related to the content of exchangeable H⁺. Due to the low cation exchange capacity of these light-textured soils the NH₃ loss was not reduced as the soil CEC increased. The maximum pH after soil amendment was related to soil pH. Therefore, a model is proposed that relates the NH₃ loss solely to fertilizers and soil pH. The NH₃ loss was less than 5% from CAN, about 20% from DAP, and about 30% from urea, with the insignificant loss from urea applied to the unlimed sandy soil excluded. The NH₃ loss from surface-applied DAP was related to the air flow rate and a transfer coefficient (K _a) was estimated. K _a increased exponentially with the flow rate. At a flow rate above 3.9 liters min^–1 (20 volume exchanges min^–1) no further increase was seen.     

A model of ammonia volatilization from applied urea. VI. The effects of transient-state water evaporation

Rachhpal-Singh & Nye's model of ammonia volatilization is further expanded to account for the effects of transient-state water evaporation when the soil surface dries significantly. Full details are given of the derivation and numerical solution of equations describing transient-state water movement, and the diffusion and convection in soil of urea and its hydrolysis products, and of acid generated by ammonia volatilization. For the wide range of soil hydraulic properties considered, the effects of a dry soil layer on the rate of volatilization supplement the effects of increased convective supply of NH⁺₄ and HCO^?₃ ions to the soil surface. The dry layer results in increased gaseous NH₃ diffusion through the soil, and thereby increases the flux of NH₃ across the soil surface and the neutralization of H⁺ ions generated by volatilization.     

缓释尿素与普通尿素配施对氨挥发和土壤氮素动态变化过程的影响

通过室内模拟试验,采用"静态吸收法"和"土壤培养法",研究了缓释尿素与普通尿素混施条件下,氨挥发和土壤中氮素的动态变化特征。结果表明:缓释掺混肥处理能减少氨挥发损失氮量;与普通尿素处理(SRU0)相比,25%缓释尿素+75%普通尿素(SRU25)、45%缓释尿素+55%普通尿素(SRU45)、65%缓释尿素+35%普通尿素(SRU65)、100%缓释尿素(SRU100)处理的氨挥发量分别降低19.88%、25.94%、42.84%和46.13%。在培养前期,普通尿素处理的土壤全氮、碱解氮和铵态氮含量明显高于缓释尿素处理,随着培养时间延长,普通尿素处理降低幅度最大,缓释掺混肥处理的全氮、碱解氮和铵态氮含量明显高于普通尿素处理;而硝态氮含量随培养时间延长逐渐升高。其中,以45%缓释尿素+55%普通尿素配比最佳,既能满足植物全生育期对养分的需求,又能减少氨挥发损失,节省经济成本。     

Influence of iron pyrites and dicyandiamide on nitrification and ammonia volatilization from urea applied to loess brown earths (luvisols)

Laboratory incubation study showed that iron pyrites retarded nitrification of urea-derived ammonium (NH₄ ⁺), the effect being greatest at the highest level (10000 mg kg^–1 soil). Nitrification inhibition with 10000 mg pyrite kg^–1 soil, at the end of 30 days, was 40.3% compared to 55.9% for dicyandiamide (DCD). The inhibitory effect with lower rates of pyrite (100–500 mg kg^–1) lasted only up to 9 days. Urea+pyrite treatment was also found to have higher exchangeable NH₄ ⁺-N compared to urea alone. DCD-amended soils had the highest NH₄ ⁺-N content throughout. Pyrite-treated soils had about 7–86% lower ammonia volatilization losses than urea alone. Total NH₃ loss was the most with urea+DCD (7.9% of applied N), about 9% more than with urea alone. Received: 11 November 1995     

A model of ammonia volatilization from applied urea. V. The effects of steady-state drainage and evaporation

Rachhpal-Singh & Nye's model of ammonia volatilization is expanded to account for the effects of steady-state water movement by drainage or evaporation when the soil does not dry out to any great extent. The model shows how upward movement of water during evaporation increases volatilization by carrying urea-derived NH₄⁺ and HCO₃^? ions upward, thereby increasing the concentration of ammonia gas at the surface. Conversely, water drainage reduces volatilization by carrying the dissolved solutes into the soil. The model is used to assess the effects on volatilization of evaporating conditions and of irrigation or rainfall.