Ammonia Volatilization from Soil,Dry-Matter Yield,and Nitrogen Levels of Italian Ryegrass

Nitrogen (N) loss by ammonia (NH₃) volatilization is the main factor for poor efficiency of urea fertilizer applied to the soil surface. Losses can be suppressed by addition of zeolite minerals to urea fertilizer. The objective of this study was to evaluate ammonia volatilization from soil and dry-matter yield and nitrogen levels of Italian ryegrass. A greenhouse experiment was carried out with the treatments of urea, urea incorporated into soil, urea + urease inhibitor, urea + zeolite, ammonium nitrate, and unfertilized treatment. Ammonia was captured by a foam absorber with a polytetrafluoroethylene tape. There were few differences between zeolite and urease inhibitor amendments concerning NH₃ volatilization from urea. Results indicate that zeolite minerals have the potential to improve the N-use efficiency and contributed to increasing N uptake. Zeolite and urea mixture reduced 50% the losses by volatilization observed with urea.     

灌溉水盐度对滴灌棉田土壤氨挥发的影响

【目的】氨挥发是农田氮素损失的重要途径之一,咸水灌溉直接或间接影响土壤的理化性质,进而影响土壤氨挥发,但目前对于咸水灌溉下氨挥发的报道还较少。因此通过田间试验研究尿素滴灌施肥条件下,淡水和咸水灌溉对棉田土壤氨挥发的影响。【方法】试验设置淡水和咸水两种灌溉水,其电导率(EC)分别为0.35和8.04d S/m(分别用CK和SW表示),氮肥(N)用量为240 kg/hm2。氨挥发的收集采用密闭室法,用稀硫酸作为氨的吸收液,测定用靛酚蓝比色法。【结果】1)灌溉施肥后,咸水滴灌棉田土壤盐分、脲酶活性和铵态氮含量均显著高于淡水滴灌。SW处理土壤电导率(EC1∶5)较CK平均高出4.53倍。灌溉施肥后SW处理土壤脲酶活性迅速增加,第4天达到最大,随后降低,SW处理脲酶活性较CK处理平均增加了20.6%。SW处理土壤铵态氮含量明显高于CK处理,尤其是灌溉施肥后第2天,SW处理铵态氮含量比CK处理增加了66.1%。2)SW处理棉田土壤p H值低于CK处理,但在灌溉施肥周期内都呈先增加后降低趋势,p H的变化在7.6~8.0之间。3)SW处理抑制了硝化作用,SW处理土壤硝态氮含量较CK处理显著降低。SW处理土壤硝态氮含量平均较CK低7.68%。4)3个灌溉施肥周期的平均温度分别为24.6℃、26.05℃和24.9℃,因此在第2个和第3个灌溉施肥周期氨挥发高,第1个灌溉施肥周期的总降水量最大,分别比第2和3个灌溉施肥周期高3.7 mm和10.2 mm,但降水量远远小于灌溉量,因此对于氨挥发影响不大。5)总体上,土壤氨挥发损失量在灌溉施肥后1~2天最大,占氨挥发总量的45.7%~79.3%,随后呈降低趋势;灌溉施肥后第1天土壤氨挥发最大,在3个灌溉施肥周期,SW处理第1天的氨挥发较CK分别增加70.7%、69.43%和60.8%。SW处理棉田土壤氨挥发显著高于CK处理。在三个连续灌溉施肥周期内,SW处理棉田土壤氨挥发累积总量为10.98 kg/hm2,CK处理为7.57 kg/hm2,SW处理较CK处理增加了45.1%。【结论】咸水灌溉促进了脲酶活性,但抑制了土壤的硝化作用,导致铵态氮含量增加,加剧了氨的挥发。温度升高促进土壤氨挥发,少量降雨对氨挥发影响不大。因此,滴灌施肥条件下,咸水灌溉会增加氨挥发损失。     

Effects of Temperature and Soil Type on Ammonia Volatilization from Slow-Release Nitrogen Fertilizers

Ammonia (NH₃) volatilization is the major pathway for mineral nitrogen (N) loss from N sources applied to soils. The information on NH₃ volatilization from slow-release N fertilizers is limited. Ammonia volatilization, over a 78-d period, from four slow-release N fertilizers with different proportions of urea and urea polymer [Nitamin 30L (liquid) (L30), Nitamin RUAG 521G30 (liquid) (G30), Nitamin 42G (granular) (N42), and Nitroform (granular) (NF)] applied to a sandy loamy soil was evaluated. An increase in temperature from 20 to 30 °C increased cumulative NH₃ volatilization loss in the sandy soil by 1.4-, 1.7-, and 1.8-fold for N42, L30, and G30, respectively. Increasing the proportion of urea in the slow-release fertilizer increased NH₃ volatilization loss. At 30 °C, the cumulative NH₃ volatilization over 78 d from a sandy soil accounted for 45.6%, 43.9%, 22.4%, and <1% of total N applied as N42, L30, G30, and NF, respectively. The corresponding losses in a loamy soil were 9.2%, 3.1%, and 1.7%. There was a significantly positive correlation between NH₃ volatilization rate and concentration of NH₄-N released from all fertilizers, except for NF (n = 132; r = 0.359, P = 0.017 for N42; r = 0.410, P = 0.006 for L30; and r = 0.377, P < 0.012 for G30). Lower cumulative NH₃ volatilization from a loamy soil as compared to that from a sandy soil appeared to be related to rapid nitrification of NH₄-N in the former soil than that in the latter soil. These results indicate the composition of slow-release fertilizer, soil temperature, and soil type are main factors to dominate NH₃ volatilization from slow- release fertilizers.     

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.     

Calcium chloride and ammonium thiosulfate as ammonia volatilization inhibitors for urea fertilizers

Abstract

Surface‐applied urea fertilizers are susceptible to hydrolysis and loss of nitrogen (N) through ammonium (NH₃) volatilization when conditions favorable for these processes exist. Calcium chloride (CaCl₂) and ammonium thiosulfate (ATS) may inhibit urease activity and reduce NH₃ volatilization when mixed with urea fertilizers. The objective of this study was to evaluate the effectiveness of CaCl₂ and ATS as urea‐N loss inhibitors for contrasting soil types and varying environmental conditions. The proposed inhibitors were evaluated in the laboratory using a closed, dynamic air flow system to directly measure NH₃ volatilization. The initial effects of CaCl₂ on ammonia volatilization were more accentuated on an acid Lufkin fine sandy loam than a calcareous Ships clay, but during volatilization periods of ≥ 192 h, cumulative N loss was reduced more on the Ships soil than the Lufkin soil. Calcium chloride delayed the commencement of NH₃ volatilization following fertilizer application and reduced the maximum N loss rate. Ammonium thiosulfate was more effective on the Lufkin soil than the Ships soil. For the Lufkin soil, ATS reduced cumulative urea‐N loss by 11% after a volatilization period of 192 h. A 20% (v/v) addition of ATS to urea ammonium nitrate (UAN) was most effective on the coarse textured Lufkin soil whereas a 5% addition was more effective on the fine textured, Ships soil. Rapid soil drying following fertilizer application substantially reduced NH₃ volatilization from both soils and also increased the effectiveness of CaCl₂ but not ATS. Calcium chloride and ATS may function as limited NH₃ volatilization inhibitors, but their effectiveness is dependent on soil properties and environmental conditions.     

Controlled‐release urea decreased ammonia volatilization and increased nitrogen use efficiency of cotton

Excessive nitrogen (N) fertilizer input leads to higher N loss via ammonia (NH₃) volatilization. Controlled‐release urea (CRU) was expected to reduce emission losses of N. An incubation and a plant growth experiment with Gossypium hirsutum L. were conducted with urea and CRU (a fertilizer mixture of polymer‐coating sulfur‐coated urea and polymer‐coated urea with N ratios of 5 : 5) under six levels of N fertilization rates, which were 0% (0 mg N kg⁻¹ soil), 50% (110 mg N kg⁻¹ soil), 75% (165 mg N kg⁻¹ soil), 100% (220 mg N kg⁻¹ soil), 125% (275 mg N kg⁻¹ soil), and 150% (330 mg N kg⁻¹ soil) of the recommended N fertilizer rate. For each type of N fertilizer, the NH₃ volatilization, cotton yield, and N uptake increased with the rate of N application, while N use efficiency reached a threshold and decreased when N application rates of urea and CRU exceeded 238.7 and 209.3 mg N kg⁻¹ soil, respectively. Ammonia volatilization was reduced by 65–105% with CRU in comparison to urea treatments. The N release characteristic of CRU corresponded well to the N requirements of cotton growth. Soil inorganic N contents, leaf SPAD values, and net photosynthetic rates were increased by CRU application, particularly from the full bloom stage to the initial boll‐opening stage. As a result, CRU treatments achieved significantly higher lint yield by 7–30%, and the N use efficiency of CRU treatments was increased by 25–124% relative to that of urea treatments. These results suggest that the application of CRU could be widely used for cotton production with higher N use efficiency and lower NH₃ volatilization.     

Nitrogen losses by volatilization in a corn crop with two tillage systems in the Argentine Pampa

Abstract

Ammonia volatilization from soils is a complex process generally associated with surface applied nitrogen (N) fertilizer. The effect of conventional tillage and no tillage on NH₃ volatilization was evaluated on cultivated corn (Zea maize L.) field in Pampa Húmeda, Argentina. The objectives of this study were a) to determine the amount of N loss by volatilization (NH₃) from urea fertilized soils under two different tillage systems (conventional and no tillage) and two different fertilizer application methods (surface and incorporated application) and b) to relate volatilization losses with environmental factors and biochemical and microbiological properties. This experiment was conducted on a Vertic Argiudoll with a silty clay loam texture in the Argentine Pampa. The site has been in natural grassland for 8 years prior was planted to corn. Following the fertilizer application for conventional tillage and no tillage systems, the daily volatilization loss of NH₃ on the fertilized plots was highest during the first three days. Higher losses of NH₃ occurred in the no‐tillage treatments, with 11.5% and 6.2% of N‐urea lost when the fertilizer was surface applied and incorporated, respectively. For conventional tillage, 8.6 % of the N was lost when the fertilizer was surface applied and 5.4% when the fertilizer was incorporated. Surface application of urea stimulated urease enzyme activity. An opposite effect was observed when the urea was incorporated. Environmental changes conditioned the availability of energy substrates for microorganisms, which resulted in different rates of intensity of biochemical reactions in the soil. Multiple regression equations showed differences between surface applied urea and incorporated urea treatments due to the latter avoiding the direct exposure of the fertilizer to atmospheric conditions.     

Control of ammonia volatilization with N‐(N‐butyl) thiophosphoric triamide in loamy sands

Abstract

In a laboratory study, ammonia (NH₃) was trapped from 10 g soil units treated with 10 mg urea‐N, 10 mg urea‐N plus 50 ug N‐(n‐butyl) thiophosphoric triamide (NBPT), or 10 mg urea‐N plus 50 ug phenyl‐phosphorodiamidate (PPD). The soil was a Dothan loamy sand with pH levels adjusted to 6.0, 6.5, and 6.9 prior to N application. After 12 days, NBPT reduced NH₃ volatilization 95 to 97%, while PPD reduced it 19 to 30%. Although NH₃ loss was positively related to initial soil pH, there was no interaction between pH and urease inhibitor. In a field study, NH₃ was trapped in semi‐closed chambers from 134 kg N/ha surface applied to corn (Zea mays L.) 6 weeks after planting. Nine days after N application, NH₃ losses were 20.5, 1.5, 1.5, and 0.2 kg N/ha from urea, urea plus 0.25% NBPT, urea plus 0.50% NBPT, and ammonium nitrate, respectively. Covariance analysis showed that percent organic matter was negatively related to NHL losses. The soil properties, initial pH, CEC, and percent sand, did not vary enough to affect NH₃ volatilization. In conclusion, in both the laboratory and the field, NBPT exhibited strong control of NH₃ volatilization, and could thereby prevent significant loss of surface‐applied urea‐N to crops.     

Urea nitricphosphate for cool‐season grass production

Abstract

Significant losses of nitrogen (N) can occur via volatilization of ammonia (NH₃) when non‐incorporated broadcast applications of urea or urea‐containing fertilizers are made. This study was conducted to determine the efficacy of urea nitricphosphate (UNP) as an N and phosphorus (P) source for cool‐season grasses and to evaluate NH₃ volatilization potential of UNP as compared to urea under laboratory conditions. A three‐year field study compared UNP to ammonium nitrate (AN) and urea at 56 and 112 kg N/ha for tall fescue (Festuca arundinacea Schreb.) and smooth brome (Bromus inermis Leyss.). Brome yields were significantly higher from UNP as compared to urea for one of the three years. No such differences occurred with fescue. Nitrogen uptake was significantly higher from UNP as compared to urea for one year each for brome and fescue. Phosphorus uptake by brome was significantly higher from UNP as compared to urea for two years. Laboratory incubation studies showed significantly lower NH₃ volatilization from UNP than from urea after seven days, but no significant differences after 14 days. The delay in NH₃ volatilization was due to the diffusion and subsequent hydrolysis of urea immediately below the soil zone initially influenced by the UNP. The reduction in NH₃ volatilization at the early time could partially be attributed to an inhibition of urea hydrolysis and significantly lower soil pH values for UNP as compared to urea in the upper 30 mm of soil cores. The general conclusion from the field and laboratory work was that UNP is a suitable N source for cool‐season grasses, with the primary potential benefit being delayed NH₃ volatilization as compared to urea.     

Ammonia volatilization from nitrogen fertilizers surface-applied to corn (Zea mays) and grass pasture (Dactylis glomerata)

Summary The major agronomic concern with NH₃ loss from urea-containing fertilizers is the effect of these losses on crop yields and N fertilizer efficiency. In this 2-year study, NH₃ volatilization from surface-applied N fertilizers was measured in the field, and the effects of the NH₃ losses detected on corn (Zea mays L.) and orchardgrass (Dactylis glomerata L.) yield and N uptake were determined. For corn, NH₄NO₃ (AN), a urea-AN solution (UAN), or urea, were surface-broadcast at rates of 0, 56 and 112 kg N ha^–1 on a Plano silt loam (Typic Argiudoll) and on a Fayette silt loam (Typic Hapludalf). Urea and AN (0 and 67 kg N ha^–1) were surface-applied to grass pasture on the Fayette silt loam. Significant NH₃ losses from urea-containing N sources were detected in one of four corn experiments (12%–16% of applied N) and in both experiments with grass pasture (9%–19% of applied N). When these losses occurred, corn grain yields with UAN and urea were 1.0 and 1.5 Mg ha^–1, respectively, lower than yields with AN, and orchardgrass dry matter yields with urea were 0.27 to 0.74 Mg ha^–1 lower than with AN. Significant differences in crop N uptake between N sources were detected, but apparent NH₃ loss based on N uptake differences was not equal to field measurements of NH₃ loss. Rainfall following N application markedly influenced NH₃ volatilization. In corn experiments, NH₃ loss was low and yields with all N sources were similar when at least 2.5 mm of rainfall occurred within 4 days after N application. Rainfall within 3 days after N application did not prevent significant yield reductions due to NH₃ loss from urea in grass pasture experiments.     

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.     

Structural Characteristics and Oxygen Consumption of the Epipelic Biofilm in Three Lowland Streams Exposed to Different Land Uses

Ammonia (NH₃) emission from nitrogen (N) fertilizers used in agriculture decreases N uptake by the crop and negatively impacts air quality. In order to better understand the factors influencing NH₃ emission from agriculture, this research was conducted with four major soils used for potato production: Biscayne Marl Soil (BMS, pH 7.27), and Krome Gravelly Loam (KGL, pH 7.69) from Florida; and Quincy Fine Sand (QFS, pH 6.65), and Warden Silt Loam (WSL, pH 6.46) from Washington. Potassium nitrate (KNO₃), ammonium nitrate (NH₄NO₃), ammonium sulfate ((NH₄)₂SO₄) or urea ((NH)₂CO) sources were evaluated for ammonia volatilization at 75 kg N ha^?1 rate. The soil water regime was maintained at either 20 or 80% of field capacity (FC), and incubated at 11, 20 or 29°C. Results indicated that NH₃ volatilization rate at 20% FC was 2 to 3-fold greater than that at 80% FC. The cumulative volatilization loss over 28 days ranged from 0.21% of N applied as NH₄NO₃ to 25.7% as (NH₄)₂SO₄. Results of this study demonstrate that NH₃ volatilization was accelerated at the low soil water regime. Moisture quotient (Q) is defined as a ratio of NH₃ emission rate at 20% FC to that at 80% FC both at the same temperature. The peak Q values of NH₃ volatilization were up to 20.8 for the BMS soil at 20°C, 112.9 for the KGL soil at 29°C, 19.0 for the QFS soil at 20°C, and 74.1 for the WSL soil at 29°C, respectively. Thus, maintaining a suitable soil water regime is important to minimize N-loss via NH₃ volatilization and to improve N uptake efficiency and air quality.     

添加脲酶抑制剂NBPT对麦秆还田稻田氨挥发的影响

氨挥发是稻田氮素损失的重要途径,为探明脲酶抑制剂NBPT对小麦秸秆还田稻田中氨挥发的影响,采用密闭室通气法,在太湖地区乌珊土上,研究了脲酶抑制剂n-丁基硫代磷酰三胺(NBPT)对小麦秸秆还田稻田中施肥后尿素水解和氨挥发动态变化的影响。结果表明:稻田氨挥发损失主要集中在基肥和分蘖肥时期。添加NBPT可明显延缓尿素水解,推迟田面水NH4+-N峰值出现的时间,并降低NH4+-N峰值,降低了田面水氨挥发速率和挥发量。NBPT的效果在基肥和分蘖肥施用后尤为明显,不加NBPT时施入的尿素在2~3 d内基本水解彻底,NH4+-N和氨挥发速率在第2 d即达到峰值,两次施肥后NH4+-N峰值分别为132.3 mg·L-1和66.3mg·L-1,氨挥发峰值为15.6 kg·hm-2·d-1和10.4 kg·hm-2·d-1;而添加NBPT后,NH4+-N峰值推迟至施肥后第4 d出现,NH4+-N峰值降至70.7 mg·L-1和51.6 mg·L-1,氨挥发峰值降至4.7 kg·hm-2·d-1和2.6 kg·hm-2·d-1。添加NBPT使稻田氨挥发损失总量从73.3 kg(N)·hm-2(占施氮量的24.4%)降低至34.5 kg(N)·hm-2(占施氮量的11.5%),降低53%。在添加小麦秸秆稻田中添加NBPT通过延缓尿素水解而显著降低了氨挥发损失。     

Enhanced-efficiency nitrogen fertilizers reduce winter losses of nitrous oxide,but not of ammonia,from no-till soil in a subtropical agroecosystem

Nitrogen (N) gas losses can be reduced by using enhanced-efficiency N (EEN) fertilizers such as urease inhibitors and coating technologies. In this work, we assessed the potential of EEN fertilizers to reduce winter losses of nitrous oxide (N₂O-N) and ammonia (NH₃-N) from a subtropical field experiment on a clayey Inceptisol under no-till in Southern Brazil. The EEN sources used included urea containing N-(n-butyl) thiophosphoric triamide (UR+NBPT), polymer-coated urea (P-CU) and copper-and-boron-coated urea (CuB-CU) in addition to common urea (UR) and a control treatment without N fertilizer application. N₂O-N and NH₃-N losses were assessed by using the static chamber method and semi-open static collectors, respectively. Both N₂O-N and NH₃-N exhibited two large peaks with an intervening period of low soil moisture and air temperature. Although the short-term effect was limited to the first few days after application, UR + NBPT urea decreased soil N₂O-N emissions by 38% relative to UR. In contrast, urease inhibitor technology had no effect on NH₃-N volatilization. Both coating technologies (CuB-CU and P-CU) were ineffective in reducing N losses via N₂O production or NH₃ volatilization. The N₂O emission factor (% N applied released as N₂O) was unaffected by all N sources and amounted to only 0.48% of N applied—roughly one-half the default factor of IPCC Tier 1 (1%). Based on our findings, using NBPT-treated urea in the cold winter season in subtropical agroecosystems provides environmental benefits in the form of reduced soil N₂O emissions; however, fertilizer coating technologies provide no agronomic (NH₃) or environmental (N₂O) advantages.     

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.     

Soil properties affecting volatilization of ammonia from soils treated with urea

Abstract

The effects of various soil properties on ammonia (NH₃) volatilization from soils treated with urea were studied by measuring the NH₃ evolved when 20 soils selected to obtain a wide range in properties were incubated at ‐0.034 mPa soil moisture potential and 30°C for 10 days after treatment with urea. The nitrogen (N) volatilized as NH₃ from these soils represented from 0 to 65% of the urea‐N applied and averaged 14%. Simple correlation analyses showed that loss of NH₃ was negatively correlated (P<0.1%) with cation‐exchange capacity, silt content, and clay content and was positively correlated (P <0.1%) with sand content. Loss of NH₃ was also negatively correlated with total nitrogen content (P<1.0%), organic carbon content (P<1.0%), hydrogen ion buffering capacity (P<5.0%), and exchangeable acidity (P<5.0%), and was positively correlated with calcium carbonate equivalent (P <1.0%) and with soil pH after incubation with urea (P<1.0%), but was not significantly correlated with initial soil pH or soil urease activity. Multiple linear regression analyses indicated that the amount of urea N volatilized as NH₃ from the 20 soils studied increased with increase in sand content and decreased with increase in cation‐exchange capacity. They also indicated that soil texture and cation‐exchange capacity are better indicators of potential loss of urea N as NH₃ from soils fertilized with urea than are hydrogen ion buffering capacity or initial soil pH.     

Urea N uptake efficiency of ryegrass (Lolium perenne L.) in the presence of urease inhibitors

Summary A greenhouse experiment was conducted to study the comparative efficiency of urea as an N fertilizer with and without the addition of different urease inhibitors. Ryegrass (Lolium perenne L.) was used as the test plant and the N balance technique with ¹⁵N was applied. Three urease inhibitors, hydroquinone, phenyl phosphorodiamidate (PPDA), and N-(n-butyl) phosphorothioic triamide (NBPT), were evaluated for their effects on urea-N uptake as well as on grass yield. The addition of urease inhibitors, except for hydroquinone in the later growth period, did not significantly influence the dry matter weight. Throughout the whole growth period, only NBPT significantly increased the total urea-N uptake. In the uninhibited system, the major fertilizer N loss occurred during the first period of grass growth, presumably via NH₃ volatilization, since the environment did not favour the other pathways of N loss. However, an appreciable amount of urea N was lost during the later growth period in all inhibited systems, especially in the hydroquinone-treated system. This indicates that the application of urease inhibitors could not eliminate the urea N loss. The greater N loss in the hydroquinone-treated soil appears to be related to the inhibition by hydroquinone of nitrification.     

Ammonia volatilization from poultry manure-amended soil

Summary Poultry manure (PM) is commonly applied to cropland as a fertilizer, usually at rates determined by the nitrogen content of the manure. Limited information is available, however, on the volatilization of ammonia from poultry manure-amended soils, despite the effect these losses may have on the fertilizer value of the manure. This study was initiated to determine the influence of incorporation and residue cover on NH₃ losses from PM-amended soils. In the first experiment, a dynamic flow technique was used to measure NH₃ losses from 18 manures applied to a bare soil surface at a rate of 12 Mg ha^-1. In the second experiment, 3 of the 18 manures were incorporated either immediately, 24 h or 72 h after application. The third experiment compared the same three manures applied to a bare soil surface or to corn or soybean residues. Surface application of the manures resulted in the loss of from 4 to 31% of the total N applied in the manures. Incorporation of the PM with soil significantly reduced NH₃ loss with the greatest decrease following immediate incorporation. Crop residues either had no effect or slightly reduced NH₃ volatilization losses relative to PM application to a bare soil surface. Ammonia volatilization was not well correlated with individual manure properties, but a multiple regression approach using manure pH and total N content offered some promise as a means to segregate manures of the basis of volatilization potential.     

Reduction in Ammonia Loss by Applying Urea in Combination with Phosphate Sources

A laboratory experiment was carried out to study the influence of 100 mg phosphorus pentoxide (P₂O₅) kg^–1 soil from various phosphate sources on ammonia losses from soils amended with urea at 200 mg nitrogen (N) kg^–1 soil. Irrespective of soil type, ammonia (NH₃) loss was significantly greater from untreated soil (control) than from the soil treated with phosphorus (P) sources. A maximum decrease in ammonia loss (56%) was observed by applying phosphoric acid followed by triple and single superphosphate. Ammonia losses were significantly greater from sandy clay loam than from clay. Rate of ammonia volatilization was maximum during the first week of incubation and became undetectable for both soils at 21 days after incubation. The addition of phosphate sources significantly decreased pH in the sandy clay loam, but in the clay a significant decrease was observed only with the phosphoric acid addition. Addition of phosphate fertilizers was beneficial in reducing NH₃ losses from urea.     

界面阻隔材料对稻田产量、氮肥利用率和氨挥发排放的影响

氨挥发是稻田氮素损失的一个重要途径,有效控制稻田氨挥发对水稻增产减排具有重要意义。界面阻隔材料具有环境友好性和低成本的特点,可以作为一种截然不同的氨挥发减排方法。本研究比较分析了3种界面阻隔材料对水稻产量、氮肥利用率和氨挥发排放的影响,以期为水稻降本增效及减少环境污染提供技术支持。通过在稻田喷施表面分子膜材料和覆盖稻糠,比较了两种表面分子膜材料——聚乳酸(PLA)和卵磷脂(LEC)及稻糠(RB)施用后水稻产量及其构成、稻田田面水pH和铵态氮及硝态氮含量动态、稻田氨挥发及氮肥吸收利用的变化特征。结果表明, 3种界面阻隔材料均显著增加了水稻产量,与常规施肥对照(CKU,无添加界面阻隔材料)相比增幅分别为13.0%(RB)、21.0%(PLA)和24.1%(LEC)。增产主要是因为有效穗数的增加,其中RB和PLA处理与CKU处理差异达显著水平;每穗粒数和结实率均无显著差异。LEC处理显著提高了氮肥利用率(19.0%),但RB处理氮肥利用率显著低于CKU。与CKU处理相比,3种界面阻隔材料的添加减少12.3%～19.9%的氨挥发量。PLA处理氨挥发减排效果最佳,达显著水平;其次为LEC处理。氨挥发减排可能与界面阻隔材料添加导致的田面水pH、铵态氮浓度变化和土壤铵态氮含量的增加有关。与CKU处理相比,所有处理均增加了田面水铵态氮浓度,但同时降低了田面水pH,且在水稻分蘖期影响较明显。其中PLA处理还提高了土壤铵态氮含量。本研究表明,稻田施加界面阻隔材料是稻田氨挥发减排以及增产增效的另一种可行的技术途径。