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1.
Abstract

Nitrogen (N) can leach in porous golf greens, especially when they are flushed with high rates of irrigation. Drain water often discharges to the surface, possibly endangering surface waters with eutrophic concentrations of nitrogen. A greenhouse study was initiated to study the effects of fertilizer source and rate and irrigation schemes on leaching of nitrate and ammonium nitrogen. Simulated golf green columns were sodded with bermudagrass. Treatments were 3 fertilizer sources (20‐20‐20, ammonium nitrate, and a sulfur‐coated urea), 3 rates (zero control, 12, and 24 kg ha?1), and 2 irrigation schemes. The first was a daily rate of 0.6 mm (N.I.), and the second was the same daily rate with several flushes of 11.5 cm each (FL). Essentially no nitrogen leached for the N.I. scheme, whereas the FL treatment resulted in significant leaching of nitrate‐N. Ammonium‐N leached to a much less extent than nitrate‐N. The nitrate‐N concentration “break through” occurred earlier, the peaks were higher, and the flushes were more prominent for 20‐20‐20 and ammonium nitrate than for the sulfur‐coated urea. The sulfur‐coated urea had a gradual nitrate‐N concentration peak that tapered off slowly. The percent N leached of that applied was higher for the flushes, and all sources were the same for flushes and the high N rate (about 20%). At the low N rate and flushes, the percent leached was highest for ammonium nitrate (10.2%), 20‐20‐20 was intermediate (4.3%), and sulfur‐coated urea was the lowest (0.14%). These data show that fertilizer sources and rates can make a difference in nitrate‐nitrogen leaching but only when significant leaching is taking place as with flushing.  相似文献   

2.
Farmers are looking for better management practices to utilize animal manure as an alternative to chemical fertilizers. A 2-year field experiment was conducted to study the effects of nitrogen (N) fertilizer source and application methods to Nicholson silt loam soil in central Kentucky, USA for no-till corn (Zea mays) production. The region has a temperate climate with a mean temperature of 14.5°C and rainfall of 1300 mm year?1. Treatments included a control, 179 kg N ha?1 urea ammonium nitrate (UAN) applied as preplant and sidedress, and swine effluent that was applied by three methods: broadcast, injection, and Aerway. Injection method produced the greatest corn grain yield (11.88 Mg ha?1) and biomass yield (18.9 Mg ha?1) in 2007. Results demonstrated that the effluent application methods and the timing of UAN application may not be agronomically important for corn production in this region. Hence, more studies are needed on different soils in this region.  相似文献   

3.
Wetland rice agriculture is the major anthropogenic source of methane, an important greenhouse gas. Methane emissions are less when ammonium sulfate (AS) rather than urea is the nitrogen (N) source. However, an agronomic advantage of AS over urea has not been established. The objectives of this study were: (i) to compare the effectiveness of AS, urea, and urea plus elemental sulfur (S) as sources of N in flooded rice culture, (ii) to compare fertilizer recovery of each source of N from application at preflood (PF) and panicle initiation (PI), and (iii) to determine if there is a response to S by rice grown on a soil with a less than optimum level of available S. ‘Cypress’ rice was . drill‐seeded in a Crowley silt loam soil (fine, montmorillonitic, thermic Typic Albaqualf) of 7.25 to 10.75 mg S kg‐1. Ammonium sulfate, urea, or urea plus S was applied in split applications of 101 kg N ha‐l PF and 50 kg N ha‐1 PI. Microplots with retainers and 15N‐labeled N were used. Unlabeled N was used in field plots. Microplots were harvested at 50% heading, while field plots were harvested at maturity. Dry matter and total N accumulation at 50% heading and at maturity were similar regardless of N source. Grain dry matter yields were 8.54, 8.47, and 8.79 Mg ha‐1 for AS, urea, and urea plus S treatments, respectively. Greater N recovery was generally found from N application at PI than at PF, but this was not reflected by an increase in grain yield. No response to S was detected, although grain yields were slightly higher when S‐containing fertilizers were used. Ammonium sulfate and urea were equally effective for flooded rice production in Louisiana.  相似文献   

4.
Nitrate nitrogen losses through subsurface drainage and crop yield are determined by multiple climatic and management variables. The combined and interactive effects of these variables, however, are poorly understood. Our objective is to predict crop yield, nitrate concentration, drainage volume, and nitrate loss in subsurface drainage from a corn (Zea mays L.) and soybean (Glycine max (L.) Merr.) rotation as a function of rainfall amount, soybean yield for the year before the corn-soybean sequence being evaluated, N source, N rate, and timing of N application in northeastern Iowa, U.S.A. Ten years of data (1994-2003) from a long-term study near Nashua, Iowa were used to develop multivariate polynomial regression equations describing these variables. The regression equations described over 87, 85, 94, 76, and 95% of variation in soybean yield, corn yield, subsurface drainage, nitrate concentration, and nitrate loss in subsurface drainage, respectively. A two-year rotation under average soil, average climatic conditions, and 125 kg N/ha application was predicted to loose 29, 37, 36, and 30 kg N/ha in subsurface drainage for early-spring swine manure, fall-applied swine manure, early-spring UAN fertilizer, and late-spring split UAN fertilizer (urea ammonium nitrate), respectively. Predicted corn yields were 10.0 and 9.7 Mg/ha for the swine manure and UAN sources applied at 125 kg N/ha. Timing of application (i.e., fall or spring) did not significantly affect corn yield. These results confirm other research suggesting that manure application can result in less nitrate leaching than UAN (e.g., 29 vs. 36 kg N/ha), and that spring application reduces nitrate leaching compared to fall application (e.g., 29 vs. 37 kg N/ha). The regression equations improve our understanding of nitrate leaching; offer a simple method to quantify potential N losses from Midwestern corn-soybean rotations under the climate, soil, and management conditions of the Nashua field experiment; and are a step toward development of easy to use N management tools.  相似文献   

5.
Abstract

Field studies were conducted to determine the influence of ammonia fertilization on cotton grown in conservation tillage systems. The studies were located on a Decatur silt loam (Rhodic Paleudult) in the Limestone Valley and a Norfolk sandy loam (Typic Paleudult) in the Coastal Plain of Alabama. Winter annual legumes, crimson clover (Trifolium incarnatum L. at the Norfolk site) and hairy vetch (Vicia villosa Roth at the Decatur site) were established as whole plots along with a winter fallow area. Sources of fertilizer differing widely in their NH4+‐N contents were used for split plot treatments applied at time of cotton (Gossypium hirsutum L.) planting. Fertilizer treatments included calcium nitrate, ammonium nitrate, urea, urea with dicyandiamide, and a no N check. The cotton was planted with a strip‐till conservation planter. Nitrogen production by winter legumes was adequate to meet N requirements for cotton on the Decatur silt loam (67 kg N/ha) but not at the Norfolk sandy loam site (101 kg N/ha). Cotton populations were 24% higher in fallow than legume whole plots. Differences in plant growth and N concentrations were highly variable and treatment trends were not found. Seed cotton yields were 4% higher in fallow than legume plots. Maximum populations and yields were achieved with ammonium nitrate in fallow area and urea in legume areas.  相似文献   

6.
改性尿素硝酸铵溶液调控氮素挥发和淋溶的研究   总被引：1，自引：0，他引：1  
为了提高肥料的利用率,以尿素硝酸铵溶液为原料、聚氨酸为保护剂,复合抑制剂NBPT(N-丁基硫代磷酰三胺)和DMPP(3,4-二甲基吡唑磷酸盐)为材料,开发出改性尿素硝酸铵溶液(YUL1和YUL2),研究其对华北平原夏玉米追肥过程中的氨挥发和淋溶损失的调控效果。田间试验设置6个处理:不施氮肥(CK)、农民习惯追施尿素(CN)、优化追施尿素(CNU)、优化追施尿素硝酸铵溶液(UAN)、优化追施改性尿素硝酸铵溶液(YUL1)和优化追施改性尿素硝酸铵溶液(YUL2)。采用扫描电镜和能谱仪分析相关指标变化,在夏玉米喇叭口期追施氮肥后15d内进行田间原位连续动态观测氨挥发和土壤铵态氮和硝态氮变化,并在玉米成熟期测定产量,计算经济效益。结果表明,改性尿素硝酸铵溶液清澈无杂质,流延后成膜表面光滑、致密,抑制剂在膜表面分布均匀;能谱测试膜层表面磷硫含量增高,证明复合抑制剂与尿素硝酸铵溶液达到有效融合。在同等优化施氮量下:与CNU相比, YUL1氨挥发总量显著降低19.3%, YUL2增加9.6%;与UAN相比, YUL1、YUL2分别显著降低57.3%和42.0%。与其他施氮处理相比, YUL1和YUL2夏玉米季生长中后期0～20 cm土层依然保持相对较高的氮素含量水平,夏玉米收获后土壤硝态氮含量分别比CNU高46.0%和43.4%,比UAN高45.6%和44.7%;180～200cm土层硝态氮含量显著低于其他处理。在保证产量和净收益的同时,改性尿素硝酸铵肥料显著降低了氮素的氨挥发和淋溶损失浓度,尿酶抑制剂含量相对较高的YUL1抑制氨挥发的效果更好,硝化抑制剂含量相对高的YUL2硝态氮向下淋失的风险更小。  相似文献   

7.
Absorption and translocation of foliar applied 15N labeled S‐tetrahydrotriazone (triazone), as compared to other N forms, was evaluated in tomato plants. Triazone‐N was taken up into leaf tissue in quantities similar to urea, ammonium, and nitrate‐N when applied at a N concentration of 0.35% w/v. Although >40% of the 15N label was exported from the treated leaf after 7 days, nearly 50% of the translocated triazone 15N label accumulated in non‐treated leaf tissue as compared to only 10% or less for the other N sources. The largest percentage of the translocated urea‐, ammonium‐, and nitrate‐15N label accumulated within developing fruit tissue. Multiple (3) foliar applications of triazone and urea at concentrations of 0.94% or higher and 1.0% N (w/v), respectively, enhanced both leaf and fruit tissue N concentrations. No growth responses to foliar applied N were observed.  相似文献   

8.
Sole ammonium supply provokes negative effects on dry‐mass formation, leaf growth, and water uptake of ammonium‐sensitive plants. To study the effects of N form on nutrient and water uptake and aquaporin expression, French bean plants were grown in a split‐root system. Five treatments were compared: homogeneous nitrate (NN) and ammonium (AA) supply; spatially separated supply of nitrate and ammonium (NA); and half of the root system supplied with N‐free nutrient solution, the other half with either nitrate (N0) or ammonium (A0). Ten days after onset of treatments, root dry mass (DM) and water‐uptake rate (WUR) were significantly reduced under ammonium compared to nitrate supply. WUR from nitrate‐supplied vessels was 80% higher than that from N‐free nutrient solution, while WUR from N‐free nutrient solution was 130% higher than that from ammonium‐supplied vessels. Potassium uptake was lower under ammonium supply and the ratio of N : K uptake of treatment AA was significantly higher compared to others. High K uptake from N‐free nutrient solution of A0 plants resulted in a ratio of N : K uptake comparable to nitrate‐supplied plants, but shoot growth resembled that to plants under sole ammonium supply. Within 24 h after onset of treatments, expression of aquaporin was lower under ammonium compared to nitrate supply. From these data, it can be concluded that reduced root water transport under ammonium supply is directly related to aquaporin activity.  相似文献   

9.
Microbial‐based inoculants have been reported to stimulate plant growth and nutrient uptake. However, their effect may vary depending on the growth stage when evaluated or fertilizer applied. Thus, the objective of this study was to test the hypothesis that microbial‐based inoculants known to promote root growth and nutrient uptake will promote plant growth, enhance early root development, and increase nutrient concentrations of corn (Zea mays L.). Plants were evaluated at four different growth stages and in the presence of three different nitrogen (N) fertilizers. The microbial‐based treatments evaluated were: SoilBuilder™ (SB), a filtered metabolite extract of SoilBuilder™ (SBF), a mixture of four strains of plant growth‐promoting Bacillus spp (BM), and a water‐inoculated control. The experiment also included four fertilizer treatments: urea (U), urea‐ammonium nitrate (UAN), calcium‐ammonium nitrate (CAN), and an unfertilized control. Corn plants were evaluated at growth stages V2, V4, V6, and VT. Plant growth parameters for biomass, height, and SPAD readings were enhanced by the three microbial‐based treatments. A greater effect of microbial‐based treatments was observed when plants were evaluated at V6 and VT stages. Parameters of early root development such as total root length (TRL), root surface area (RSA), and length of fine roots were enhanced when microbial‐based treatments were applied. Concentrations of N, P, and K were also increased by microbial‐based treatments compared to the non‐inoculated control. Increases in plant N concentration due to microbial‐based treatments were on average 72% for CAN, 61% for UAN, 72% for urea, and 54% for the unfertilized control. Phosphorus concentration was increased most (138%) when BM was applied with CAN. In the same way, when CAN was present, K concentration was increased by 95% with BM and 65% when SB and SBF were applied. Overall, the results demonstrate that microbial‐based inoculants evaluated in this study can positively impact corn growth and nutrient concentration, especially during the late vegetative stages. Furthermore, the results indicate that the enhancement of nutrient concentrations (N, P, and K) in this case was related to the capacity of microbial‐based treatments to impact root morphology at early stages of corn growth.  相似文献   

10.
Abstract

Leaf N and soil nitrate and ammonium levels were monitored in 1986 and 1987 following N fertilization of 8–9 year old highbush blueberries. Urea was applied at 76 kg N/ha in a single application at bud break or in two applications (split) at bud break and petal fall. Controlled release fertilizers (CRF), of two different residual effects (Osmocote 3 mo., Osmocote 8 mo.) were applied at 38 kg N/ha or 76 kg N/ha at bud break. Compared to controls, N applications increased soil ammonium and nitrate levels early in the season and leaf N levels throughout the season. Urea provided a greater increase in leaf N and soil ammonium levels than CRF. Split urea applications increase leaf levels slightly over single urea treatments. Fertilizers increased soil ammonium and nitrate levels below the root zone, indicating that some leaching losses occurred.  相似文献   

11.
With respect to the important effects of nitrogen (N) on plant growth and fruit production, a five-year experiment was performed to evaluate the effects of different sources of N fertilization including chemical and organic on the quantity and quality of citrus fruit. Using five-year old trees, different types of fertilization including ammonium sulfate, urea coated with sulfur, ammonium nitrate and manure were tested using seven treatments in five replicates from 2002 to 2007. Different plant quantitative and qualitative parameters were determined. The most effective strategy on fruit yield production was the use of urea coated with sulfur and manure with 92.46 kg ha?1 fruit yield followed by ammonium sulfate and manure (87.06 kg ha?1) and ammonium sulfate (86.43 kg ha?1). The combination of mineral and organic fertilization may be the most suitable fertilization strategy for citrus production.  相似文献   

12.
Abstract

Chinese cabbage (Brassica rapa L. Chinensis group) production is expanding in the U. S., and guidelines regarding its production under Western cultural practices are needed. The objectives of this study were to investigate the effects of N source and rate on Chinese cabbage yield, marketability, and wrapper leaf nutrient concentrations, and to estimate the critical wrapper leaf‐N concentration associated with maximum yield and marketability. Chinese cabbage was grown in five sequential plantings using raised‐bed, polyethylene mulch culture with subsurface irrigation on a sandy soil. Nitrogen fertilizer was applied at rates of 0, 67,112, and 157 kg/ha using the following sources: 1) ammonium nitrate. 2) calcium nitrate, 3) urea‐ammonium nitrate solution (Uram, 32% N), 4) urea, and 5) a urea‐calcium solution (18% N). Mature Chinese cabbage wrapper leaf concentrations of P, Ca, and Mg increased with increasing N rate, while leaf‐K concentration decreased. Leaf‐N concentration increased in response to N rate, but was not affected by N source or harvest date. Leaf‐P, K, Mg, and B concentrations were sufficient or high according to established standards, but leaf‐Ca was low. Leaf‐Ca and Mg concentrations were lowest with N sources containing only urea, and highest where at least part of the N was applied as NO3 ‐. Chinese cabbage head weight and percentage marketable heads increased as N rate increased. Yield and quality were highest with N sources which contained NO3 ‐, and were smallest where N was applied entirely as urea, which may have been due to plant sensitivity to NH4 +. The critical value of mature cabbage wrapper leaf‐N concentration above which yield or marketability was not limited was estimated to be 36 to 41 mg/g, which agrees well with established standards.  相似文献   

13.
《Journal of plant nutrition》2013,36(7):1183-1197
Abstract

Nitrogen (N) fertilization continues to be of primary importance in the economically successful production of cotton (Gossypium hirsutum L.). Profit margins of producers might be expanded by increasing the uptake efficiency of applied N. Recently, N fertilization of crops grown in the Mississippi River Delta has been suspected to impact water quality in the Gulf of Mexico. Improving efficiency of N uptake could alleviate some environmental concerns by increasing the retention of N at the site of application. The objective of this study was to determine the impact of replacing preplant N applications with postemergent N applications on the growth and yield characteristics of cotton. Delayed applications of the recommended rate of N fertilizer (112 kg N ha?1) were tested for four years under irrigated and dry land production conditions. The N rate was applied either preplant, after crop emergence, or at first square. Further, 112 kg N ha?1 was split applied evenly at preplant + first square, and after emergence + first square. The five 112 kg ha?1 N treatments were compared to an unfertilized control. Yield tended to be maximized with N treatments that included a first square application. Yields were usually lowest in the unfertilized control and the 112 kg N ha?1 preplant treatments. Not surprisingly, both yield and plant growth was influenced more by irrigation than N fertilization. Years when drought conditions caused water stress and limited plant growth, dry land cotton had only limited response to the N fertilization treatments. Irrigated cotton responded to N treatments all years with increased growth and yield. Optimizing agronomic considerations, the best N fertilization timing was an after emergence + first square split application.

  相似文献   

14.
Effectiveness of surface-applied unincorporated broiler litter as a fertilizer relative to conventional inorganic fertilizers under no-till or conventional-till cotton (Gossypium hirsutum L.) production systems in the upland soils of the southern and southeastern USA is not well documented. The objectives of this research were to (1) test if broiler litter improves plant macronutrient (N, P, K, and Mg) nutrition of cotton above that of cotton fertilized with conventional inorganic fertilizers and (2) determine if lack of incorporating litter into the soil reduces macronutrient concentration in cotton plant parts in an upland soil considered marginal for cotton. Six treatments consisting of an unfertilized control, a fertilized standard (STD), two litter-only, and two litter plus inorganic N as urea–ammonium nitrate solution (UAN) were tested in two adjacent fields, one under no-till (NT) and the other under conventional-till (CT) systems. Litter alone, UAN, or a combination of litter plus UAN were applied to supply 101 kg ha−1 plant available N assuming nearly all of the UAN-N and 50% of the total litter N becomes plant available during the cotton growing season. Concentration of N, P, K, and Mg were measured in leaves, stems, and reproductive parts on three or four dates between early flowering and maturity. Cotton fertilized with the litter-only treatments always had less N concentration but greater P and K concentration in leaves, stems, and reproductive parts than cotton that received the STD treatment. Leaf and stem Mg concentration seems to depend on the N concentration in these plant parts. Lack of incorporating litter into the soil reduced N concentration in nearly all plant parts at all growth stages, suggesting some amount of the litter-derived N is lost due to lack of incorporation. Lack of incorporation also reduced leaf and stem Mg concentration, which seemed to be due to its reducing effect on N concentration. Unlike N and Mg, lack of incorporation did not consistently affect concentrations of P and K in all plant parts. Regardless of the incorporation treatment, fertilization with the litter-only treatments increased tissue P and K concentration and supported lint yield exceeding that of the STD without increasing tissue N concentration.  相似文献   

15.
Abstract

Ammonium thiosulfate (ATS, 12–0–0–26S) and dicyandiamide (DCD, 66–0–0) are fertilizer products that also inhibit nitrification. It has also been proposed that ATS can improve the nitrification inhibition properties of DCD. The purpose of this research was to compare the effects of ATS, DCD, and ATS/DCD mixtures on the nitrification of banded urea solution or urea‐ammonium nitrate (UAN) under laboratory, field microplot, and field conditions. The laboratory study demonstrated that adding 8.7% (vol vol‐1) ATS to a urea solution inhibited nitrification by 68%. Inhibition of nitrification was greater with ATS + DCD than with DCD alone. Some nitrite accumulated when ATS was added, but little or no nitrite accumulated when both ATS and DCD were present In field microplot studies, the addition of ATS to urea solution significantly (P ≤ 0.10) increased residual soil ammonium levels over urea alone at six of 11 trials. ATS was usually a less effective nitrification inhibitor than was DCD, and ATS + DCD outperformed DCD at only one of 11 trials. In all three field trials, adding ATS to banded UAN solution led to increased residual ammonium levels. Again, ATS was less effective than DCD or nitrapyrin as a nitrification inhibitor, and no ATS/DCD synergism was observed. It was concluded that the use of ATS as a sulfur fertilizer in fluid fertilizer bands can lead to measurable inhibition of nitrification, but ATS was not as reliable as DCD or nitrapyrin.  相似文献   

16.
The purpose of this study was to measure the effect of additives on ammonia loss when used with urea–ammonium nitrate fertilizer (UAN). The fertilizer additives were ammonium thiosulfate (ATS), calcium thiosulfate (CaTS), N-(N-butyl) thiophosphoric triamide (Agrotain, AG), AG + CaTS, or a maleic-itaconic copolymer (Nutrisphere-N, NSN). Four greenhouse studies were conducted, with small fertilizer droplets applied to bare soil, large fertilizer droplets applied to bare soil, small fertilizer droplets applied to soil with 50% straw cover, and large fertilizer droplets applied to soil with 50% straw cover. Ammonia volatilizing from the soil surface was trapped in phosphoric acid and determined by steam distillation. Averaged across all four experiments, the percentage reductions of ammonia loss after 14 days, compared to unamended UAN, were 40% for UAN + ATS, 40% for UAN + CaTS, 51% for UAN + AG, 65% for UAN + AG + CaTS, and 11% for UAN + NSN.  相似文献   

17.
We studied the effects of 15N-labelled ammonium nitrate and urea on the yield and uptake of labelled and unlabelled N by wheat (Triticum aestivum L., cv. Mexi-Pak-65) in a field experiment. The dry matter and N yields were significantly increased with fertilizer N application compared to those from unfertilized soil. The wheat crop used 33.6–51.5 and 30.5–40.9% of the N from ammonium nitrate and urea, respectively. Splitting the fertilizer N application had a significant effect on the uptake of fertilizer N by the wheat. The fertilizer N uptake showed that ammonium nitrate was a more available source of N for wheat than urea. The effective use of fertilizer N (ratio of fertilizer N in grain to fertilizer N in whole plant) was statistically similar for the two N fertilizers. The application of fertilizer N increased the uptake of unlabelled soil N by wheat, a result attributed to a positive added N interaction, which varied according to the fertilizer N split; six split applications gave the highest added N interaction compared to a single application or two split applications for both fertilizers. Ammonium nitrate gave 90.5, 33.5, and 48.5% more added N interaction than urea with one, two, and six split N applications. A values were not significantly correlated with the added N interaction (r=0.557). The observed added N interaction may have been the result of pool substitution, whereby added labelled fertilizer N replaced unlabelled soil N.  相似文献   

18.
Abstract. Broadcast granular fertilizers are inefficient at supplying nitrogen (N) to wide-spaced row crops. Substantial nitrate residues can remain in the soil post-harvest, even when recommended fertilizer practices are followed. This paper explores the benefits of an alternative strategy based on targeting small amounts of liquid nitrogen starter fertilizer close to the seed at drilling to increase N use efficiency and reduce potential pollution. Bulb onion ( Allium cepa ) and crisp lettuce ( Lactuca sativa ) were grown with various rates and combinations of ammonium phosphate (AP) and urea ammonium nitrate (UAN) as 'starters', in comparison with seedbed incorporated ammonium nitrate. AP consistently improved early growth and final yield of both crops compared to broadcast ammonium nitrate, but UAN showed no additional benefits. AP in combination with broadcast N, or injected UAN, generally increased N recovery, and produced yields of marketable quality produce matched only by much higher rates of broadcast N. A reduced N input system based on starter fertilizers is likely to be acceptable to the industry, but would rely on a method to predict how much N is required to supplement that provided by the starter.  相似文献   

19.
ABSTRACT

The effectiveness of N-(n-butyl) thiophosphoric triamide (NBPT) in reducing ammonia volatilization from urea-based fertilizers has been thoroughly investigated. However, the stability of this inhibitor during storage of NBPT treated urea and urea ammonium nitrate (UAN) needs further investigation. We compared ammonia volatilization from NBPT treated urea (360 mg NBPT kg?1 urea) and UAN (180 mg NBPT L?1 UAN) that were stored at room temperature for 6, 3 and 0 months. We measured ammonia volatilization with cylindrical chambers fitted with acid-charged discs at five times for 21 d. Total ammonia volatilization (measured as a % of applied nitrogen) was significantly greater in untreated urea and UAN (32% to 33%) than those in NBPT treated urea and UAN (6% to 12%). Reduction of ammonia volatilization was not significantly different among NBPT treated urea (73% to 81%) and UAN (63% to 73%) irrespective of storage time. This implies that farmers can mix their urea-based fertilizers with NBPT formulation 6 months prior to fertilization without compromising the ammonia volatilization reducing property of the NBPT.  相似文献   

20.
Many of the poorly drained clayey soils of the Mississippi River delta region in Arkansas are used for soft red winter wheat (Triticum aestivum L.) production. Oftentimes, excessive rainfall occurs between the last N application and physiological maturity, resulting in soil conditions conducive to denitrification. Studies were conducted in 1989 and 1990 to evaluate late N applications on five wheat cultivars on a Sharkey silty clay (very fine, montmorillonitic, nonacid, thermic, Vertic Haplaquepts) at Keiser, AR. A linear‐move irrigation system was used to maintain excessive soil moisture conditions throughout the spring growing season to best insure denitrification conditions. After the recommended spring N was applied, N as urea was applied at rates of 0, 34, and 68 kg ha‐1 at growth stage (GS) 9 in 1989 and GS 10 in 1990. Ammonium nitrate was also evaluated at the 34 kg N ha‐1 rate. Grain yield, yield components, whole‐plant N concentration, grain N content, and whole‐plant N uptake were evaluated. Grain yield increased each year with late N applications. The optimum N rate was 34 kg ha‐1 with no difference between the N sources, urea and ammonium nitrate. The yield component accounting for this grain yield increase were kernels per spike in 1989 and kernel weight and kernels per spike in 1990. Whole plant N concentration increased each year and grain N content increased in 1990 with the late N application. The N sources affected N nutrition similarly.  相似文献   

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