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1.
根据氮肥施入土壤后的转化特性进行氮肥的高效调控和管理是提高氮肥利用效率、缓解氮肥污染的重要措施。为探究不同氮肥在石灰性潮土中的转化特性差异及硫代硫酸铵（ammonium thiosulfate，ATS）作为氮肥调控剂对尿素氮转化的影响，该研究采用室内土壤培养（土壤水分含量为田间持水量的60%，温度25 ℃）试验方法，以尿素、硫酸铵、氯化铵和ATS作为供试肥料，比较4种氮肥施入石灰性潮土后的转化特性差异，并以ATS作为氮素调控剂，以单施尿素作为对照，探究尿素配施不同用量ATS对尿素氮转化的影响。结果表明，4种供试氮肥在石灰性潮土中的转化过程明显不同。尿素在石灰性潮土中的水解速率最快，硝化作用强度也最高，硫酸铵其次；氯化铵由于Cl-的硝化抑制作用，土壤表观硝化率在7～21 d显著低于尿素和硫酸铵（P＜0.05）；ATS施入土壤后，NH4+-N转化为NO2--N的速率最高，而NO2--N转化为NO3--N的速率最低，NH4+-N在土壤中的存留时间最长，出现峰值之后也一直保持最高的含量，表观硝化率最低。将ATS作为氮素调控剂与尿素配合施用，当其用量在60 mg/kg（含S量）以上时，既表现出了明显的抑制尿素水解的作用效果，也表现出了显著的硝化抑制作用（ P <0.05），且随着ATS用量的增加，抑制效应明显增强。这对于减少氮素损失，提高氮肥利用效率具有积极意义。但供试4种氮肥施入土壤后均出现了亚硝酸盐的累积，其中ATS处理的累积量显著高于尿素、硫酸铵和氯化铵（P＜0.05），累积持续时间也最长。ATS作为氮素调控剂调控氮素转化，也出现了类似的结果，且随着ATS用量增加，亚硝酸盐在土壤中存留时间明显延长，含量和峰值明显提高，出现峰值的时间也明显延后。  相似文献   

2.
Abstract

Nitrogen (N) loss in the form of volatilized ammonia (NH3) is a considerable problem when ammonium (NH4 +) forming fertilizers are applied to calcareous or alkaline soils. The volatilization of NH3 from urea phosphate (UP) and urea (U) was studied on three selected soils (Hayhook SL, Laveen L, and Latene L) with the use of a laboratory aeration system. Urea phosphate and U were each applied at rates of 0, 50, 100, and 200 mg N kg‐1 soil, either to the surface dry or in solution or mixed with the soil. The volatilized NH3 was trapped in sulfuric acid, sampled periodically, and analyzed for N with the semi microkjeldahl distillation apparatus.

The highest N loss in the form of NH3 occurred when U was applied to Hayhook soil (neutral to acidic, coarse textured, and low CaCO3 content). However, UP applied to Hayhook soil resulted in the lowest NH3‐N loss. Less NH3‐N loss was found from U application to Laveen and Latene soils (fine textured with higher CaCO3 content) than with Hayhook soil. The general trend was higher N loss when a surface application was made, either dry or in solution, than when the fertilizer was mixed with the soil. This trend showed an increase in the amount of volatilized NH3 with increasing N application rates.

Generally, UP is a potential fertilizer for supplying N and phosphorus (P) as plant nutrients with a low potential for losses due to NH3 volatilization.  相似文献   

3.
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.  相似文献   

4.
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.  相似文献   

5.
Abstract

Volatilization of ammonia derived from nitrogen (N) fertilizers and its possible reabsorption by crops depend on specific soil, climate, and atmospheric conditions, as well as the method of fertilizer application and plant architecture. In an experiment carried out in Piracicaba, State of São Paulo, Brazil, the volatilization of ammonia derived from urea, ammonium sulfate, and natural soil were quantified using static semi‐open N‐ammonia (NH3) collectors. Fertilizers were top‐dressed under the plant canopy on top of dead leaf mulch. In another experiment, the reabsorption of the volatilized ammonia by plants was quantified using 15N‐labeled urea. Results showed, as expected, that volatilization derived from urea was seven times more intense in relation to ammonium sulfate, whose volatilization was very low, and slightly more than the natural volatilization from soil at pH 5.3. The loss of ammonia from the ammonium sulfate was very low, little more than twice of that of the natural soil. Through isotopic labeling, it was verified that 43% of the volatilized N‐NH3 was reabsorbed by coffee plants, which gives evidence that volatilization losses are greatly reversed through this process.  相似文献   

6.
Volatilization of NH3 from soil is a major N-loss mechanism that reduces the efficiency of applied N fertilizers, and causes environmental pollution. Strategies are needed to reduce the loss. The influences of dicyandiamide (DCD), farmyard manure (FYM) and irrigation on NH3 volatilization from an alluvial soil in rice (Oryza sativa L.)-wheat (Triticum aestivum L.) cropping system was studied using the acid trap method. The loss of NH3 in the rice-wheat system ranged from 38.6 kg N ha-1 from the unfertilized soil to 69.0 kg N ha-1 in the treatment with urea+DCD. Substitution of 50% N provided through urea by FYM reduced NH3-N volatilization by 10% in rice and wheat as compared to the urea treatment. Application of DCD increased NH3 volatilization in wheat by 7% but in rice it had no effect. The irrigation level had no effect on NH3 volatilization in rice but fewer irrigations with fewer splits of N in wheat resulted in higher NH3 volatilization. Application of DCD and FYM with urea had similar effects on grain yield and N uptake by rice and wheat as that of the urea treatment. The study showed that integrated use of organic manure and chemical fertilizer has the potential to reduce the loss of N due to volatilization and thereby minimize environmental pollution. Nitrification inhibitors, which are reported to be useful in increasing the N-use efficiency by reducing the leaching and denitrification losses of N, however, may increase N loss due to volatilization.  相似文献   

7.
Effect of urease inhibitors on urea hydrolysis and ammonia volatilization   总被引：3，自引：0，他引：3  
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.  相似文献   

8.
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.  相似文献   

9.
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.  相似文献   

10.
Foliar sprays of calcium chloride (CaCl2) and to a lesser extent, soil applications of calcium nitrate [Ca(NO3)2] fertilizer, increased calcium (Ca) concentrations in leaves and fruit of apple, (Malus domestica) and pear (Pyrus communis L.) trees. For most years, CaCl2 sprays or Ca(NO3)2 fertilizer increased cold hardiness of ‘Anjou’ pear trees, and reduced the incidence of fruit disorders (alfalfa greening and cork spot of pears and bitter pit of ‘Delicious’ apples). Yield of ‘Anjou’ pears was usually increased with the higher rates of nitrogen (N) fertilizers [ammonium nitrate (NH4NO3), Ca(NO3)2, or urea]. Calcium chloride sprays increased yield of ‘Anjou’ pears if it was applied over many years.  相似文献   

11.
Urea replaced ammonium nitrate (AN) as a nitrogen (N) source for dryland Kentucky bluegrass seed production in the inland Pacific Northwest in the United States. This study assessed ammonia (NH3) volatilization, N recovery, and seed yield from urea as compared to AN. Laboratory incubations indicate NH3 volatilization is greater from soil covered by fresh residue than soil alone or covered by burned residue. Although pH of the fresh and burned residues exceeded 8.0, urease activity in burned residue was <15% of that in unburned residue or soil. Ammonia volatilization from dry urea and fluid urea AN was greater than AN at burned and unburned sites after a 5 October application. Ammonia volatilization was higher and N recovery and seed yield were lower for urea after a 15 November application at an unburned site. To reduce NH3 volatilization, apply urea to fields with low urease activity or moisture content and/or immediately before a significant rain event.  相似文献   

12.
 Effects of amending urea with pyrite (Py) or potassium chloride (KCl) alone and in combination with copper sulphate (CuSO4) on NH3 volatilization and N-use efficiency in an Alfisol were evaluated. NH3 volatilization from surface-applied urea fertilizers was measured using a closed dynamic air flow system. Kinetics of NH3 volatilization over a 10-day period showed that the peak rate of NH3 loss was on day 3 with the unamended urea, whilst it occurred on day 4 with all amended urea fertilizers. Total NH3 loss from the unamended urea was 48% of the applied N, which was reduced to 38 and 40% with U+Py and U+KCl, respectively. A further reduction in N loss was recorded with U+Py+CuSO4 (34%) and U+KCl+CuSO4 (36%). The inhibition of NH3 with U+Py+CuSO4 and U+KCl+CuSO4 was markedly high, at 30 and 25%, respectively. As compared to urea, all amended urea fertilizers resulted in a significantly higher dry matter yield, N uptake and apparent N recovery (ANR) efficiency by sunflower. An increase of 28 and 24% units in ANR over urea could be obtained with U+Py+CuSO4 and U+KCl+CuSO4, respectively. Since the chemical additives also have a fertilizer value besides being effective in controlling NH3 loss from urea and improving N-use efficiency, their use as amendment to urea could be a viable option. Received: 5 August 1999  相似文献   

13.
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.  相似文献   

14.
A soil column method was used to compare the effect of drip fertigation (the application of fertilizer through drip irrigation systems, DFI) on the leaching loss and transformation of urea-N in soil with that of surface fertilization combined with flood irrigation (SFI), and to study the leaching loss and transformation of three kinds of nitrogen fertilizers (nitrate fertilizer, ammonium fertilizer, and urea fertilizer) in two contrasting soils after the fertigation. In comparison to SFI, DFI decreased leaching loss of urea-N from the soil and increased the mineral N (NH4+-N + NO3--N) in the soil. The N leached from a clay loam soil ranged from 5.7% to 9.6% of the total N added as fertilizer, whereas for a sandy loam soil they ranged between 16.2% and 30.4%. Leaching losses of mineral N were higher when nitrate fertilizer was used compared to urea or ammonium fertilizer. Compared to the control (without urea addition), on the first day when soils were fertigated with urea, there were increases in NH4+-N in the soils. This confirmed the rapid hydrolysis of urea in soil during fertigation. NH4+-N in soils reached a peak about 5 days after fertigation, and due to nitrification it began to decrease at day 10. After applying NH4+-N fertilizer and urea and during the incubation period, the mineral nitrogen in the soil decreased. This may be related to the occurrence of NH4+-N fixation or volatilization in the soil during the fertigation process.  相似文献   

15.
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.  相似文献   

16.
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.  相似文献   

17.
Abstract

Interest in use of ammonium thiosulfate (ATS) in conjunction with urea as a fertilizer has been stimulated by reports that ATS retards hydrolysis of urea by soil urease. We recently found, however, that ATS significantly retarded urea hydrolysis in soil only when applied at very high rates (>2,500 (μg/g soil) that adversely affected seedling development. Because ATS is rapidly oxidized in soil, we compared the effects of thiosulfate and its oxidation products (tetrathionate, sulfite, and sulfate) on urea hydrolysis and seedling development in soil and hydrolysis of urea by jackbean urease. We found that the inhibitory effect of thiosulfate on urea hydrolysis in soil is due to tetrathionate formed by oxidation of thiosulfate and that both thiosulfate and tetrathionate have an adverse effect on seedling growth of wheat and corn in soil. Tetrathionate at concentrations of 2,500 and 5,000 μ.g/mL inhibited hydrolysis of urea by jackbean urease, whereas thiosulfate had no inhibitory effect at these concentrations. We could not confirm a hypothesis that the inhibitory effect of ATS on soil urease is due to Fe2+ and Mn2+ formed during oxidation of thiosulfate in soil.  相似文献   

18.
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.  相似文献   

19.
Ammonia losses after surface application of fresh chicken slurry (15% solids) and anaer-obically stored chicken slurry (10% solids) to a silty clay soil (pH 6.9) at a rate equivalent to 34 m3 ha?1 were studied in a laboratory incubation experiment. Total NH3-N losses amounted to 29% of the initial uric acid-N+urea-N+NH+4-N content of the fresh slurry and 28% of the initial NH+4-N content of the anaerobic slurry. Peak rates of ammonia volatilization took place between 24 h and 48 h after application of the fresh slurry and within 5 h of application of the anaerobic slurry. The addition of CaCl2 at a rate of 36 mg Ca g?1 (dry wt) slurry decreased peak rates of ammonia volatilization from the fresh slurry by 73% and total losses by 37%. The decrease in total ammonia losses through CaCl2 addition to the anaerobic slurry was only 8 %. The addition of CaCl2 decreased CO2 output from both slurries through precipitation of HCO3? as CaCO3, thereby removing a source of alkalinity from the solution. The failure of the CaCl2 addition to decrease significantly ammonia losses from the anaerobic slurry suggested that HCO3? was an important source of alkalinity driving ammonia volatilization in the fresh slurry, but not in the anaerobic slurry. CaCl2, addition did not affect urea hydrolysis, nor net nitrogen mineralization. The decrease in ammonia loss achieved through CaCl2 addition was however not associated with a parallel increase in ammonium concentrations in the soil. Further experiments showed that the ammonia retained by the CaCl2, was probably fixed by the soil and rendered non-extractable by KCl.  相似文献   

20.
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.  相似文献   

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