Untreated Urea Research Articles

Efficiencies of nitrogen fertilizers for winter cereal production, with implications for greenhouse gas intensities of grain

SUMMARYFertilizer nitrogen (N) accounts for the majority of the greenhouse gas (GHG) emissions associated with intensive wheat production, and the form of fertilizer N affects these emissions. Differences in manufacturing emissions (as represented in the current carbon accounting methodologies) tend to favour urea, even when using the best available manufacturing technologies (BAT), whereas differences in fertilizer N efficiency and emissions of ammonia tend to favour ammonium nitrate (AN). To resolve these differences, data from 47 experiments in two large UK studies conducted from 1982 to 1987 and from 2003 to 2005 were reanalysed, showing that on average urea efficiency was 0·9 of AN (although mean ammonia emissions in 10 subsidiary experiments indicated an efficiency difference of 0·2); treating urea with a urease inhibitor (TU; AGROTAIN®, active ingredient N-(n-butyl) thiophosphoric triamide (n-BTPT)) brought its efficiency almost in line with AN; however, a significantly greater mean optimum N amount for TU (+0·1 of AN) was not fully explained. A standard response function relating wheat yield to applied AN was modified for degrees of relative inefficiency, thus enabling yields and GHG intensities (kg CO2e/tonne (t) grain) to be calculated using a PAS2050 compatible model for GHG emissions for any N amount of any N form. With AN manufactured by average European technology (AET), the estimated GHG intensity of wheat producing 8 t/ha was 451 kg/t; whereas with urea or TU made by AET it was 0.87–0.99 or 0.84–0.86 of this respectively. Using BAT for fertilizer manufacture, the grain's GHG intensity with AN and TU was 368 kg/t, but was 1·03–1·17 of this with untreated urea. The range of effects on GHG intensities arose mainly from remaining uncertainties in the inefficiencies of the N forms. Generally, economic margins and GHG intensities were not much affected by adjustments in N use for relative inefficiencies or different prices of urea-based fertilizers compared with AN. Overall, TU appeared to provide the best combination of economic performance and GHG intensity, unless the price for N as TU exceeded that for N as AN.

Comparison of Enhanced‐Efficiency Nitrogen Fertilizers for Reducing Ammonia Loss and Improving Bermudagrass Forage Production

The efficacy of enhanced‐efficiency (EE) nitrogen (N) fertilizer formulations in reducing N loss and improving the efficiency of urea‐based fertilizer products in forage production is unclear. This study compared ammonium nitrate (AN), urea, four EE urea N formulations [N‐(n‐butyl) thiophosphoric triamide (NBPT)–treated urea, NBPT and dicyanamide–treated urea, a polymer‐coated urea (PCU), and a maleic‐itaconic copolymer–treated urea (MICPU)], urea–ammonium nitrate (UAN), and two EE UAN formulations (NBPT‐treated UAN, NBPT and dicyanamide–treated UAN) in forage bermudagrass [Cynodon dactylon (L.) Pers.] production. The experimental design was a randomized complete block design with four replications in each of two sites and 2 yr (2008–2009). Treatment applications were made at the rate of 168 kg N ha−1 spring dormancy‐break (ca. 30 April) and after the second harvest (ca. 25 July; total of 336 kg N ha−1 season). Response variables included trapped ammonia (NH3) and forage yield, production efficiency, N concentration, N uptake, recovery of applied N, and nitrate concentration. Urea treated with NBPT reduced NH3 volatilization and, in some situations, increased agronomic response relative to urea. Addition of NBPT produced results similar to AN and UAN, and it was never detrimental relative to untreated urea. The MICPU treatment was ineffectual relative to urea alone. The PCU reduced NH3 volatilization and improved N concentration in the forage but did not improve other agronomic characteristics. Use of UAN solutions produced results that were generally intermediate in response between urea and ammonium nitrate and were not improved by NBPT addition. Adding NBPT can reduce NH3 volatilization and increase the efficiency of urea, but further research is necessary to understand the limits of this additive.

Relative efficiency of prilled urea coated with major neem (Azadirachta indica A. Juss) oil components in lowland irrigated rice of the Indo-Gangetic plains

The fertilizer nitrogen use efficiency (NUE) in lowland rice is quite low (20–50%) in India. Coating of nitrification inhibitors, such as neem cake or neem oil, onto prilled urea may improve NUE. Hence, a field experiment was conducted at the Indian Agricultural Research Institute, New Delhi, during the wet seasons of 2005 and 2006 to study the effect of prilled urea coated with varying doses of major neem oil components on grain yield and NUE of scented rice. Sixteen treatments comprised of combinations of five major neem oil components (free fatty acid, pure oil, meliacins, saturated and unsaturated fractions)-coated prilled urea with three doses (500, 1000 and 5000 mg kg−1). An additional treatment of prilled urea alone (untreated urea) was also taken. The experiment was laid out in a randomized block design with three replications. Results suggest that the coating of prilled urea with meliacins proved the most effective in enhancing yield and NUE of rice as compared to uncoated prilled urea or coated with other neem oil components. Across all the neem oil components, a coating thickness of 500 mg kg−1 onto prilled urea was sufficient to realize the higher yield and NUE of lowland irrigated rice.

Controls of Volatile Ammonia Losses from Loblolly Pine Plantations Fertilized with Urea in the Southeast USA

Ammonia volatilization losses from surface applied urea could reduce the N‐use efficiency in loblolly pine (Pinus taeda L.) plantations. Three field studies were conducted to assess the effectiveness of two urea formulations: coated‐urea fertilizer (CUF) and the urease inhibitor N‐(n‐butyl) thiophosphoric triamide‐treated urea (NBPT) at reducing ammonia (NH3) losses in loblolly pine plantations under different forest floor moisture (dry vs. wet), substrate (forest floor vs. mineral soil), and site/soil type conditions (Piedmont vs. Coastal Plain). An additional laboratory study under controlled environmental conditions helped validate the results from the field. Ammonia volatilization losses were influenced more by the initial forest floor moisture than by the fertilizer formulations and were 43% lower when the fertilizer treatments were applied directly on the forest floor than on the exposed mineral soil. The average NH3 losses, expressed as a percentage of applied N, in the Piedmont ranged from 1 to 9%, and from 7 to 16%, 7 and 30 d after fertilization, respectively. At Day 7, both CUF and NBPT reduced NH3 losses, as compared with untreated urea, by 39 and 80%, respectively. In the Coastal Plain, NH3 losses ranged from 7 to 17%, 7 d after fertilization. Both CUF and NBPT reduced NH3 losses, as compared with untreated urea, by 35 and 25%, respectively. This difference in treatment ranking between sites suggests a fertilizer by site/soil type interaction which the laboratory study confirmed. These results highlight the importance of knowing the environmental and site conditions before fertilization and can help decide where and when these formulations might be used more effectively.

Banding of Urea Increased Ammonia Volatilization in a Dry Acidic Soil

Volatilization of ammonia following application of urea contributes to smog formation and degradation of natural ecosystems. The objective of this study was to evaluate the impact of (i) incorporation and banding of urea and (ii) surface broadcast of slow-release urea types on NH(3) volatilization in a dry acidic soil. Volatilization was measured using wind tunnels for 25 d after standard urea (140 kg N ha(-1)) was broadcast, broadcast and incorporated (0-5 cm), or incorporated in shallow bands (3-5 cm) to a conventionally tilled silty loam soil. Urea supplemented with a urease inhibitor or coated with a polymer was also broadcast at the soil surface. Little N diffused out of the polymer-coated granules and ammonia losses were low (4% of applied N). Use of a urease inhibitor also resulted in a low NH(3) loss (5% of applied N) while maintaining soil mineral N at levels similar to plots where untreated urea was broadcast. The rate of hydrolysis of urea broadcast at the soil surface was slowed by the lack of moisture and NH(3) loss (9% applied N) was the lowest of all treatments with standard urea. Incorporation of broadcast urea increased emissions (16% applied N) by increasing urea hydrolysis relative to surface application. Furthermore, incorporation in band also increased emissions (27% applied N) due to a localized increase in soil pH from 6.0 to 8.7. We conclude that incorporating urea in bands in a dry acidic soil can increase NH(3) volatilization compared to broadcast application followed by incorporation.

RESPONSE OF TWO MAIZE HYBRIDS TO UREA FERTILIZATION UNDER APPLICATION OF HYDROQUINONE UREASE INHIBITOR.

Two field experiments were conducted during 2004 and 2005 summer seasons at Gaziret-Hanout,Kafr Sakr District, Sharkia Governorate, Egypt to study the response of two maize hybrids (SC 122 and TWC 310) to three levels of urea fertilization levels (75,100 and 125 kgN/fad) under application of three hydroquinone (HQ) urease inhibitor levels (0, 2.25 and 3.25 kg HQ/100 kg N). The adopted experimental design was split-split plot with three replicates. The results revealed that TWC 310 maize hybrid was superior in each of plant height, number of ears /plant, number of rows/ ear, number of grains / row, number of grains / ear, 100 - grain weight, oil percentage and both grain and oil yields / fad compared to SC122 which superior in ear length and protein percentage. However, both tested hybrids gave almost the same protein yield/fad. Increasing N levels from 75 to 100kg N/fad resulted in a significant increase in plant height, 100-grain weight, protein percentage and protein yield/fad, while the increase in urea-N levels up to 125kgN/fad increased significantly all other studied characters, except oil percentage which significantly decreased by any increase in N levels up to 125KgN/fad. Treating urea fertilizer with HQ urease inhibitor at the rate of 2.25kgHQ/100 kg N increased significantly both plant height and 100-grain weight, while increasing HQ levels up to 3.25kgHQ/100 kg N resulted in a significant increase in the other most studied characters compared with untreated urea. Any further HQ increment caused further reduction in oil percentage. Regarding the interaction effects, TWC 310 gave the higher number of grains/ ear when urea was treated with 3.25kgHQ/100kgN with a response rate of 25.66. Grain yield/ fad was responded to urea-N up to 100 kg N/fad when 2.25 or 3.25kg HQ/100kg N was added. The highest oil yield / fad was attained when 125 kg N/fad was applied and when urea treated with 3.25 kg HQ/100 kg N. The results revealed positive and significant correlation coefficients between grain yield/ fad, and most of studied characters, while negative and significant correlation was found for grain yield related to oil percentage. The path analysis revealed that the direct effect of number of ears/plant was 17.06% being higher than that of 100-grain weight and number of grains/ear which was 15.18 and 5.11% of maize grain yield variation, respectively. Regression analysis revealed that number of ears/ plant and number of grains/ ear are similar to that of grain yield and each is of quadratic relationship with urea-N fertilization, while the response of 100-grain weight to urea-N fertilizer had a linear relationship. Hence, grain yield of maize could be increased by splitting the suitable nitrogen amount in order to be active in increasing 100-grain weight.

Milk production efficiency improvement in buffaloes through the use of slow ammonia release and protected protein supplement

To study the effect of feeding Slow Ammonia Release and Protected Protein supplement (SARPP) on blood urea nitrogen (BUN) and urinary levels of allantoins as well as on quantity and quality of milk, a feeding trial was conducted on 24 lactating buffaloes. Animals were divided into three similar groups, fed on standard basal ration. Animals in group-I were fed 1.0 kg untreated rapeseed meal containing 50 g untreated urea, animals in group II were fed 1.0 kg treated rapeseed meal containing 50 g untreated urea and animals in group III were fed 1.0 kg treated rapeseed meal containing 50 g treated urea (SARPP supplement), in place of one kg compound cattle feed. Levels of BUN and allantoins in urine were 10.33, 10.48 & 9.64 (P<0.05) mg/dl and 2.35, 3.03 & 5.23 (P<0.01) mmol/litre in groups I, II and III, respectively. Daily average milk yield was 6.46, 7.42 (P<0.05) and 7.70 (P<0.01) kg in groups I, II and III, respectively. Average fat and protein % were 6.64 & 3.41, 6.81 (P<0.05) & 3.53 and 6.95 (P<0.05) & 3.57 in groups I, II and III, respectively. On feeding SARPP supplement, crop residues and dietary proteins could be utilized in a more efficient manner in buffaloes.

Valor nutritivo do feno de braquiária amonizado com uréia ou inoculado com Pleurotus ostreatus

Verificou-se, mediante análises de composição química e ensaio de digestibilidade com ovinos, o efeito dos tratamentos químico (amonização com uréia) e biológico (inoculação com o fungo Pleurotus ostreatus) sobre o valor nutritivo do feno de Brachiaria decumbens. Ambos os tratamentos duraram 42 dias; após esse período, o feno foi seco e moído para fornecimento aos animais. As dietas experimentais foram: feno não tratado (FNT); feno não tratado + uréia (FNT + U); feno inoculado com fungo + uréia (FTB + U); e feno amonizado + feno não tratado (FTQ + FNT). As dietas FNT + U, FTB + U e FTQ + FNT foram isonitrogenadas. Tanto o tratamento químico como o biológico causaram mudanças na composição química do feno. A amonização elevou os teores de proteína bruta (PB) e fibra em detergente ácido (FDA) e reduziu os teores de hemicelulose (HEM) e a proporção de hemicelulose na parede celular (HEM-FDN). Já o tratamento biológico tendeu a aumentar o teor de PB; elevou os teores de FDA, lignina (LIG), a proporção de celulose na parede celular (CEL-FDN) e a proporção de lignina na parede celular (LIG-FDN); e reduziu os teores de fibra em detergente neutro (FDN), HEM e HEM-FDN. Entretanto, diminuiu a digestibilidade da matéria seca (MS), FDN, celulose (CEL) e FDA, mas aumentou o consumo, provavelmente em decorrência do menor teor de FDN e menor tamanho médio de partículas, o que causou maior velocidade de passagem. Os tratamentos biológico e químico são alternativas importantes no incremento do valor nutritivo de materiais lignocelulósicos, todavia, os resultados obtidos neste ensaio não foram satisfatórios.

Effect of seed-placed urea fertilizer and N-(n-butyl)thiophosphoric triamide (NBPT) on emergence and grain yield of barley

Seedling damage from excess seed-placed urea fertilizer can be a major problem in one-pass seeding and fertilizing systems. Field studies were conducted on a clay loam and a fine sandy loam soil over 3 yr to evaluate the impact of seed-placed urea N, with and without the addition of the urease inhibitor N-(n-butyl) thiophosphoric triamide (NBPT) on stand density and growth of barley. Seedling damage, as indicated by reduction in stand density, occurred on both soil types at rates of seed-placed N as low as 40 kg N ha−1. Addition of NBPT to the urea fertilizer increased stand density at N levels where damage occurred with the untreated urea. Dry matter yield at heading generally was unaffected by N application or use of NBPT; however, final yield was increased by use of NBPT in four of five site-years. Use of NBPT appears promising as a method of reducing the risk of seedling damage from seed-placed urea fertilizer, thus increasing the rate of urea-N that can be safely placed with the seed. Key words: Urease inhibitor, seedling toxicity, ammonia

Differences in microbial fermentation of barley straw induced by its treatment with anhydrous ammonia

AbstractThe effect of ammonia treatment of straw on both the rumen environment and the extent of its microbial fermentation was studied. Four rumen cannulated sheep were randomly given 700 g/day of untreated straw plus urea (US), ammonia-treated straw (TS) and alfalfa hay (AH) in a change-over design with three periods. Rumen pH was lower and ammonia-nitrogen and total volatile fatty acid (VFA) concentrations were higher (P &lt; 0·001) with AH than with US or TS. With the straw diets, TS promoted a lower pH than US (P &lt; 0·05), but differences were less than 0·3 units and the mean pH was never below 6·5. There were no differences between the straw diets in ammonia-nitrogen or VFA concentration (P &gt; 0·05). When untreated barley straw (BS) and treated straw (TS) were incubated in situ disappearance of dry matter (dDM) at 12, 24 and 48 h (P &lt; 0·01) and neutral-detergent fibre (dNDF) at 48 h (P &lt; 0·001) were higher with TS. In vitro incubation showed a higher gas production with TS only after 36 h (P &lt; 0·05) whereas gas from BS fermentation was higher up to 14 h (P &lt; 0·05). Among diets, dDM, dNDF and gas production with US were numerically higher than with TS or AH throughout, although few significant differences were observed, except for a higher dDM at 12 (P &lt; 0·01) and 24 (P &lt; 0·10) h and a higher dNDF at 12 h (P &lt; 0·10). Particle-associated enzymes were extracted from BS and TS incubated in the rumen for 4, 8, 22 and 24 h. Results ofxylanase and cellulase activities support those of straw incubation, with a drop between 4 and 8 h in TS diet. The concentration of residual phenolics per unit of incubated straws after 12 and 24 h show that phenolics release to the media was higher with the TS diet. Daily changes of phenolic concentration into rumen liquid was also higher with TS than with US (P &lt; 0·001). The increased release of straw phenolics by ammoniation reduced the potential for rumen degradation of straw, mainly in the first hours of the fermentation period.

Evaluation of Nitrification Inhibitors and Urea Placement in No‐Tillage Winter Wheat

AbstractNitrification inhibitors (NIs) such as dicyandiamide (DCD) and nitrapyrin [2‐chloro‐6‐(trichloromethyl)pyridine] (NP) slow the nitrification process, thus reducing N losses from leaching and denitrification. In field studies (1990–1994) on a Renfrow silt loam (fine‐silty, mixed, thermic Udertic Paleustolls) near El Reno, OK, we evaluated these two NIs and their placement effects on nitrification of applied urea in soils and on wheat (Triticum aestivum L.) yields. Urea at 60 kg N ha−1 treated with or without NIs was placed 3 to 4 cm below the seed (BL) at seeding or was broadcast (BR) after seeding on the day of seeding, with no N as control. Mineral N forms were determined in the 0‐ to 30‐cm soil zone in fall and spring. Differences in soil mineral N concentration below the 10‐cm depth were minimal (but higher than the control) in all N treatments. In the 0‐ to 10‐cm depth, BL placement of NI‐treated urea significantly reduced nitrification in the fall compared with BR urea with or without NIs, except in 1994. Soil mineral N content in spring was similar with either placement of NI‐treated urea, but was significantly greater than untreated BR urea. Warm temperatures and dry soil in the fall tended to reduce the effectiveness of surface‐applied NIs. The highest NH4+ percentage in total soil mineral N was observed with DCD BL or NP BL, followed by NP BR and DCD BR. Urea treated with NIs increased grain yield from 7 to 31% above untreated urea. Grain yield was highest with DCD BL (31%), followed by DCD BR (26%) and NP BR (24%), compared with the broadcast untreated urea. Grain N yield was 140 g kg−1 greater with DCD‐N than with untreated urea. Deep placement of DCD under no‐till winter wheat in the southern Great Plains can reduce nitrification and increase N availability under varying year‐to‐year environmental conditions and can improve wheat grain yield and grain N compared with surface broadcast of urea with or without NI.

INFLUENCE OF NITRIFICATION INHIBITORS ON NUTRIENT AVAILABILITY, YIELD AND UPTAKE IN RICE SOILS.

A field experiment was conducted in sandy clay loam soil to study the effect of nitrification inhibitors on nutrient availability, yield and uptake of nutrients by rice. The available nitrogen (N), phosphorous (P) and potassium (K) contents were higher in treatments with 75 per cent N as nitrification inhibitors and the rest as prilled urea (PU). The nimin coated urea (NICU) treatments showed higher grain and straw, yields than neem cake coated urea (NCU) and PU treatments. Nitrification inhibitors applied treatments recorded higher N. P and K uptake than untreated urea treatment.

Ammonia Volatilization from Urea as Influenced by Soil Temperature, Soil Water Content, and Nitrification and Hydrolysis Inhibitors

AbstractResidue cover influences temperature and water gradients in the soil profile. Changes in the physical environment of the soil influence NH3 volatilization from urea‐containing fertilizers. Field and laboratory experiments were conducted to investigate the influence of residue‐cover‐induced changes in soil water and temperature on NH3 volatilization as impacted by urea treatment with a nitrification and urease inhibitor. Fertilizer treatments were urea, urea plus dicyandiamide (DCD), urea plus N‐(n‐butyl)thiophosphoric triamide (NBPT), and urea plus NBPT and DCD. Following fertilizer application, the soil was either left bare or covered with corn (Zea mays L.) residue. Every 3 h over a 4‐d period, water potential, soil temperature, CO2 production, and NH3 volatilization were measured. The influence of fertilizer treatments on soil pH was determined in a laboratory incubation experiment conducted over 8 d under controlled environmental conditions. Treatments were similar to the field experiment, with NH3 volatilization, pH, and CO2 production measured daily. The NH3‐volatilization rate in the field was highest 2 d after urea application at a time that corresponded with daily maximum soil temperature and decreasing soil water content. Residue cover reduced NH3 volatilization. Volatilization of NH3 as a result of urea application was not increased when urea was treated with DCD. Ammonia volatilization as a result of urea treatment with NBPT was reduced by 100 times over untreated urea. During an incubation experiment, soil pH increased from 6.5 to 7.2 in the urea‐NBPT, and from 6.5 to 9.0 in the urea and urea‐DCD treatments. Associated with the pH increase in the urea‐NBPT treatment was a reduction in CO2 production when compared with the untreated soil.

Temperature and low concentration effects of the urease inhibitor N-(n-butyl) thiophosphoric triamide (nBTPT) on ammonia volatilization from urea

The effect of the urease inhibitor N-(n-butyl) thiophosphoric triamide (nBTPT) on urea hydrolysis and NH 3 volatilization was studied in laboratory experiments. At ambient laboratory temperatures. NH 3 volatilization rates were shown to be significantly reduced by an nBTPT concentration in urea as low as 0.005% (w/w). After 8 days, at ambient laboratory temperatures, NH 3 loss from urea was 37.7%. whereas losses from the 0.005 and 0.05% nBTPT products were 13.6 and 1.8%. respectively. Higher concentrations of nBTPT were required at 32°C than at 18°C to achieve equivalent suppression of NH, loss. A direct relationship was not observed between inhibition of urea hydrolysis and the concomitant reduction in NH 3 loss. After 4 days at ambient laboratory temperatures, 65% of untreated urea had been hydrolyzcd. whereas hydrolysis from the 0.01% product was 42%. Over the same period, NH 3 losses amounted to 12.3 and 1.8%, respectively. In the soils evaluated, effective inhibition of urea hydrolysis and NH 3 volatilization was obtained with very low concentrations of nNBPT, but higher concentrations were necessary at higher temperatures and in soils that had been amended with plant residues. The effect of nBTPT on loss may not have been due solely to delayed urea hydrolysis per se; rather, this delay may have also resulted in greater diffusion of urea into the soil and thus lowering the NH 3 concentrations at the microsites on the soil surface.

Effects of dicyandiamide (a nitrification inhibitor) on leaching of nitrogen and growth of cereals

Dicyandiamide (DCD) was tested as a nitrification inhibitor with urea in 10 field experiments (ammonium nitrate was included in 2 of them) in 3 years on sites where leaching of nitrogen was a potential problem. The investigations included different rates and times of nitrogen application. At 1 site in 1982 and 2 in 1983 the soil was sampled to 30cm throughout the season. Nitrification of ammonium nitrogen was delayed by DCD (applied as a mixture with urea and supplying 10% ofthe nitrogen in the mixture) by up to 30 days compared with untreated urea and reduced the danger of nitrogen leaching. Early sampling at the 1982 site showed increased uptake of ammonium nitrogen and decreased nitrate nitrogen in wheat plants receiving DCD-treated urea compared with those receiving untreated urea. This confirmed that DCD inhibits nitrification. The only significant (P&lt;0.05) grain yield increase from DCD was a 22% increase from an application of nitrogen at sowing on a particularly highly leaching soil. DCD significantly (P &lt; 0.05, P &lt; 0.01) reduced grain yield (7 and 8%) and vegetative yield (1 3 and 9%) at 2 sites. DCD increased vegetative yield by 16% at 1 site (not the same site as the grain yield increase). In 2 of 3 experiments plant dry matter production (up to 11 weeks after sowing) was significantly (P &lt; 0.05 to P &lt; 0.001) reduced (up to 30%) by DCD application. The final value of the use of DCD will depend on the balance between the benefit in preventing nitrogen losses by leaching at a particular site and the harm caused by suppressing early plant growth.

Nitrate Leaching Losses from Monolith Lysimeters as Influenced by Nitrapyrin

AbstractThree monolith lysimeters, each with a surface area of 8.1 m2 and a depth of 2.4 m, were planted to no‐till corn (Zea mays L.) for 6 consecutive years. The lysimeters contained a Rayne silt loam (Typic Hapludult), a well‐drained residual soil. Urea was placed in a slot approximately 10‐cm deep and 10 to 15 cm from the corn row at a rate of 336 kg N/ha. The urea applied to two of the lysimeters was treated with nitrapyrin [2‐chloro‐6‐(trichloromethyl)pyridine], a nitrification inhibitor, and applied untreated on the third lysimeter. Two years of unfertilized meadow immediately preceded the corn. Concentrations of NO−3; in the leachate from the lysimeters were higher during the corn years than during the meadow period. Concentrations showed seasonal variations during the last 3 yr of the study, but showed no increasing trend. The leachate from the lysimeters receiving the nitrapyrin treated urea had seasonally flow‐weighted NO−3; concentrations ranging from 6 to 40 mg/L, while the leachate from the lysimeter receiving untreated urea had seasonally flow‐weighted NO−3;‐N concentrations ranging from 20 to 54 mg/L. Nitrate‐N losses showed a similar treatment difference. The 6‐yr annual average NO−3; loss was 117 and 160 kg/ha from the lysimeters with the treated urea and untreated urea, respectively. This study demonstrates that nitrification inhibitors such as nitrapyrin, have a potential to reduce NO−3; leaching when applied with ammoniacal fertilizers.

Different nitrogen sources for fertilizing western hemlock in western Washington

Effects of different sources of fertilizer N on selected chemical characteristics of soils and foliage, and on growth of western hemlock (Tsugaheterophylla (Raf.) Sarg.) were compared at three different sites in western Washington. Treatments were the following: untreated control (O), ammonium nitrate (AN), ammonium sulfate (AS), calcium nitrate (CN), urea (U), and urea – ammonium sulfate (US). Fertilizers were applied in the spring (April–May) at 224 kg N/ha. Forest floor and mineral soil, to a depth of 5 cm, and foliage were sampled periodically for 2 years. Height and diameter of selected trees were measured periodically for 4 years. Results are reported mostly for two sites, one in the Cascade Range and one in the coastal zone in western Washington. The pH of forest floor and mineral soil varied by treatment, and the two urea fertilizers caused substantial initial rise. Effects on soil and foliar nutrients varied by fertilizer, sampling date, and location. In general, all fertilizers increased NH4 N, N03 N, and total N in the forest floor and mineral soil, and total N in the foliage. Also, with some exceptions, especially with foliar P in the Cascade site, fertilization reduced foliar content of important nutrients. At the Cascade site, 4-year growth responses in height, basal area, and volume averaged over all fertilizers were 30, 34, and 32%, respectively. AN, AS, CN, and urea resulted in height growth significantly (P &lt; 0.20) higher than that of the control. Significant basal area growth and volume-growth responses were produced by AN, CN, and US. No significant height-growth response to any fertilizer occurred in the coastal stand; basal area growth and volume-growth responses averaged 27 and 21%, respectively, and best response occurred with urea. These results suggest that the low and inconsistent response of hemlock to N fertilization cannot be improved by applying some N fertilizer other than urea. Factors limiting response to N fertilization may be associated with availability of native N and other nutrients or other characteristics of hemlock sites and stands.

Untreated and formaldehyde-treated urea as nitrogen sources for lactating dairy cows

An experiment was performed with 22 Friesian cows, using a double reversal design with two treatments and one similar sequence for the two groups. The lengths of the standardization period, adaptation periods, test period and post-test period were 4, 1, 8 and 4 weeks, respectively. During the standardization and post-test periods the cows received pre-wilted grass silage ad libitum and a small amount of field-dried baled hay. In the test period hay was given ad libitum and the amount of grass silage was restricted. A concentrate mixture (barley, oats, minerals) was given daily to each cow at the rate of 0.3 kg/kg 4 % milk. During the standardization and post-test periods the mixture contained one percent of untreated urea and during the test period 2.5 % of untreated or treated urea. The urea had been treated with 1.5 % formaldehyde on a weight basis. The concentrate mixture was fed individually to each cow, but group feeding was used for the roughage. Among the cows producing more than 15 kg of 4 % milk a day, those receiving formaldehyde-treated urea had a significantly (P&lt; 0.01) higher milk yield, and the fat content of their milk was significantly (P&lt; 0.05) lower than the group receiving untreated urea. Among the cows producing less than 15kg of 4 % milk/day, the group given treated urea had a significantly (P

Untreated and formaldehyde-treated urea as nitrogen sources for young growing bulls

Untreated urea and urea treated with 1.5 % formaldehyde were compared as nitrogen sources for young growing bulls. The experiment was performed with 12 individually fed animals, eight of which were Friesians and four Finnish Ayrshires, and the average age of the animals at the beginning of the experiment was about 3.5 months. After a standardization period of two weeks, the animals were divided into two groups with similar distributions by daily gain, feed utilization, liveweight and age. During the following transition period of one week the feeding of the animals was changed to the experimental diets of the 24-week test period. The feeding was based on NaOH-treated barley straw and a mixture of barley, oats and molassed beet pulp, and planned for a daily gain of 1000 grams/animal. During the standardization period the animals received 2.9 % untreated urea in the concentrate, and soybean meal was also used to bring the feeding into agreement with the standards chosen. During the test period the animals received untreated or treated urea and their contributed about 35—40 % of their DCP requirements. There were no significant differences between the groups in daily gain, feed utilization or slaughter results. Nor did the two groups show any significant differences in plasma urea, albumin and total proteins. The plasma concentrations of aspartate aminotransferase, alanine amino transferase and creatinine did not differ significantly between the groups.

Effect of the crude protein level on the utilization of untreated and formaldehyde-treated urea in vitro

Utilization of untreated urea (F0) and urea treated with 1.5 % formaldehyde(F1.5) was tested in vitro on incubation substrates with different levels of crude protein: 9, 10, 11, 12, 13, 14, 15 and 16 % of the substrate dry matter. The content of crude protein was adjusted by addition of urea, the lowest level (9 %) being that of the substrate without urea. The incubation time was five hours. When F0 urea was used microbial protein synthesis, determined by tungstic acid-sulphuric acid precipitation, reached its maximum at the crude protein level of 11 %. When F1.5 urea was added, the synthesis increased up to the level of 15 % crude protein. At the levels of 13-15% crude protein, the synthesis was significantly (P&lt; 0.05) higher with F1.5 urea than with F0 urea. In the bacterial mass obtained by ultracentrifugation the content of methionine was significantly higher (P&lt; 0.01) when treated urea was used. With untreated urea, the proportion of lysine was significantly higher (P&lt; 0.05). Addition of urea did not affect the amino acid composition of the bacterial mass but increased the yield of microbial protein during incubation.