NH3-N Losses Research Articles

Nitrogen Recovery and Loss from Kentucky Bluegrass Fertilized by Conventional or Enhanced-Efficiency Urea Granules

Easy handling and low unit N cost make prilled urea (46-0-0) a popular fertilizer. While incomplete recovery of granular urea applications by turfgrass is documented, field evaluations of NH3 volatilization mitigation by coatings or bioinhibitor efficiency enhancements are limited. Meanwhile, NH3 emissions reduce air quality and contribute to nutrient loading of water resources. Our objectives were to quantify 3- and 6-d ammonia emission and 9-week turfgrass recovery of unincorporated granular fertilizer application to turfgrass. In 2014 and 2015, commercial urea-N fertilizers were broadcast over a mature Kentucky bluegrass (Poa pratensis L. ‘Midnight’) lawn at 43 kg ha−1. Treatments included conventional urea and three enhanced-efficiency fertilizers; a blended fertilizer with 25% of its urea-N supplanted by polymer- and polymer-/sulfur-coated prills, or two stabilized urea fertilizers both amended by N-(n-butyl) thiophosphoric triamide (NBPT) and dicyandiamide (DCD) inhibitors. Using a 51% ‘trapping-efficiency’ flux chamber system under the field conditions described, 23.1 or 33.5% of the conventional urea-N was lost as NH3 over the respective 3- or 6-d period following application. Alternatively, dual amendment by NBPT and DCD resulted in approximately 10.3 or 19.6% NH3-N loss over the respective 3- or 6-d periods, and greater fertilizer-N recovery by the turfgrass over the 9-week experiments.

Advanced Processing of Food Waste Based Digestate for Mitigating Nitrogen Losses in a Winter Wheat Crop

The anaerobic digestion of food waste converts waste products into ‘green’ energy. Additionally, the secondary product from this process is a nutrient-rich digestate, which could provide a viable alternative to synthetically-produced fertilisers. However, like fertilisers, digestate applied to agricultural land can be susceptible to both ammonia (NH3) and nitrous oxide (N2O) losses, having negative environmental impacts, and reducing the amount of N available for crop uptake. Our main aim was to assess potential methods for mitigating N losses from digestate applied to a winter wheat crop and subsequent impact on yield. Plot trials experiments were conducted at two UK sites, England (North Wyke-NW) and Wales (Henfaes-HF), to assess NH3 and N2O losses, yield and N offtake following a single band-spread digestate application. Treatments examined were digestate (D), acidified-digestate (AD), digestate with the nitrification inhibitor DMPP (D+NI), AD with DMPP (AD+NI), and a zero-N control (C). Determination of N losses was conducted using wind tunnels for NH3, and static manual and automatic chambers for N2O. The N offtake in both grain and straw was also measured. Ammonium nitrate (NH4NO3) fertiliser N response plots (from 75 to 300 kg N ha−1) were included to compare yields with the organic N source. Across both sites, cCumulative NH3-N losses were 27.6 % from D and D+NI plots and 1.5 % for AD and AD+NI of the total N applied, a significant reduction of 95 % with acidification. Cumulative N2O losses, varied between 0.13 and 0.35 % of the total N applied and were reduced by 50 % with the use of DMPP although the differences were not significant. Grain yields for the digestate treatments were 7.52 – 9.21 and 7.23 – 9.23 t DM ha−1 at HF and NW, respectively. Yields were greater from the plots receiving acidified-digestate relative to the non-acidified treatments but the differences were not significant. The yields (as a function of the N applied with each treatment) obtained for the digestate treatments ranged between 84.2 % (D+NI) and 103.6 % (D) of the yields produced by the same N rate from an inorganic source at HF. Advanced processing of digestate

Ammonia volatilization following urea application at maize fields in the East African highlands with different soil properties

Use of nitrogen (N) fertilizer is underway to increase in Sub-Saharan Africa (SSA). The effect of increasing N rates on ammonia (NH3) volatilization—a main pathway of applied-N loss in cropping systems—has not been evaluated in this region. In two soils (Alfisols, ALF; and Andisols, AND) with maize crop in the East African highlands, we measured NH3 volatilization following urea broadcast at six rates (0–150 kg N ha−1) for 17 days, using a semi-open static chamber method. Immediate irrigation and urea deep placement were tested as mitigation treatments. The underlying mechanism was assessed by monitoring soil pH and mineral N (NH4+ and NO3−) concentrations. More cumulative NH3-N was volatilized in ALF than in AND at the same urea-N rate. Generally, higher urea-N rates increased proportional NH3-N loss (percent of applied N loss as NH3-N). Based on well-fitted sigmoid models, simple surface urea application is not recommended for ALF, while up to 60 kg N ha−1 could be adopted for AND soils. The susceptibility of ALF to NH3 loss mainly resulted from its low pH buffering capacity, low cation exchange capacity, and high urease activity. Both mitigation treatments were effective. The inhibited rise of soil pH but not NH4+ concentration was the main reason for the mitigated NH3-N losses, although nitrification in the irrigation treatment might also have contributed. Our results showed that in acidic soils common to SSA croplands, proportional NH3-N loss can be substantial even at a low urea-N rate; and that the design of mitigation treatments should consider the soil’s inherent capacity to buffer NH3 loss.

Ammonia Emissions from Dairy Lagoons in the Western U.S.

Abstract. Ammonia (NH3) emissions from dairy liquid storage systems can be a source of reactive nitrogen (N) released to the environment, with a potential to adversely affect sensitive ecosystems and human health. However, little on-farm research has been conducted to estimate these emissions and determine the factors that may affect these emissions. Six lagoons in south-central Idaho were monitored for one year using open-path Fourier transform spectrometry, with NH3 emissions estimated using inverse dispersion modeling (WindTrax software). Lagoon physicochemical characteristics thought to contribute to NH3 emissions were also monitored over this period. Average total emissions from the lagoons ranged from 12 to 43 kg NH3 ha-1 d-1, or 5.4 to 85 kg NH3 d-1. Emissions from the settling basin on one dairy were 30% of the total emissions from the liquid storage system, indicating that basins are important sources of on-farm NH3 emissions. Emissions generally trended greater during the summer, when temperatures were greater. High wind events and agitation of the lagoons created temporary increases in NH3 emissions irrespective of temperature. Lagoon physicochemical characteristics, such as total Kjeldahl nitrogen (TKN) and total ammoniacal nitrogen (TAN), were highly correlated with emissions (r = 0.52 and 0.55, respectively). Regression models were developed to predict on-farm NH3 emissions and indicated that TKN, TAN, wind speed, air temperature, and pH were the main drivers of these emissions. An on-farm N balance suggested that lagoon NH3-N losses represented 9% of total N lost from the facility, 65% of total lagoon N, and 5% of dairy herd N intake. A process-based model (Integrated Farm System Model) estimated values for N excretion and NH3-N loss from the lagoon within 5% of that measured on-farm. More on-farm research is needed to better refine both process-based models and emission factor estimates to more accurately predict NH3 emissions from lagoons on dairies in the western U.S. Keywords: Ammonia, Emission, Inverse dispersion, Manure.

Urease Inhibitor and Irrigation Management to Mitigate Ammonia Volatilization from Urea in No-Till Corn

High nitrogen (N) losses by ammonia (NH3) volatilization from urea can compromise nitrogen fertilization efficiency and corn yield. The purpose of this study was to assess the effects of irrigation management and the addition of the urease inhibitor N-(n-butyl)thiophosphoric triamide (NBPT) on NH3-N losses from urea and on corn yield. To this end, two experiments were carried out in the 2011/12 crop season on a sandy clay loam Acrisol in the Central Basin region of Rio Grande do Sul, southern Brazil. Experiment I consisted of two different N sources (urea and urea plus the inhibitor) at a rate of 200 kg ha-1 N and two corn sowing times [viz., an early time (Sept. 3, 2011) and an intermediate time (Oct. 3, 2011)]. Experiment II considered a combination of three irrigation management systems (viz., without irrigation on the fertilization day and on the next 7 days; 20 mm of water immediately before N fertilization; and 20 mm water after N fertilization) and two N sources (urea and urea plus the inhibitor) at 150 kg ha-1 N. A control treatment without topdressed N fertilization was also performed in parallel with the two experiments. The NH3-N losses from common urea increased with increasing soil moisture in Experiment I (25 % applied N), and with irrigation before N fertilization in Experiment II (27 % applied N). The inhibitor reduced NH3-N losses from urea by 46 to 80 %. Also, irrigation after fertilization reduced ammonia volatilization by 83 % on average, with little effect from the inhibitor. The effects of the inhibitor and post-fertilization irrigation on the mitigation of NH3 losses by volatilization from urea were not additive; in addition, they led to no increase in corn yield.

Effects of Dairy Slurry Injection on Carbon and Nitrogen Cycling

Surface broadcast of dairy slurry is a common practice; however, concerns over nuisance odors and nutrient losses have prompted research into alternatives. Manure injection is one practice that addresses these concerns but is not widely adopted. Therefore, two studies were conducted to quantify NH3-N loss by volatilization, impacts on soil N cycling, and microbial response between surface broadcast and subsurface injection of dairy slurry. A constant air flow volatilization chamber system measured NH3-N losses and soil inorganic N, mineralizable carbon, and active microbial biomass. A 40-day static air incubation was performed to study nitrogen transformations over a longer period after application. Statistical significance was evaluated at the α = 0.05 level. In the volatilization study, subsurface injection reduced NH3-N losses by 98% and 87% in a clay loam and sandy loam, respectively, resulting in greater soil inorganic nitrogen compared with surface application. There were no significant differences in active microbial biomass between treatments. Surface application prompted greater microbial respiration in the sandy loam, but there were no significant differences between treatments in the clay loam. In the static incubation study, differences in soil NO3-N became significant on day 28, and by day 40, injection showed increases in soil NO3-N of 13% and 26% in the sandy loam and clay loam, respectively, relative to surface application. While the effect of subsurface injection on soil microbial response was unclear, it remains a tool that can greatly reduce NH3-N losses by volatilization and increase soil plant available nitrogen.

Urea deep placement for minimizing NH3 loss in an intensive rice cropping system

It is urgently necessary to reduce environmental harm while simultaneously ensuring food security from agriculture in China. Fertilizer deep placement, especially urea deep placement (UDP), has been widely recognized as an efficient way to increase rice yield with less N use in flooded rice fields; however, few studies have explored UDP as a way to abate N loss, particularly ammonia (NH3) volatilization, in intensive rice cropping systems. Therefore, a field experiment was performed in the Taihu Region with five treatments (two surface split broadcasting treatments: a current traditional practice with 300kgNha−1 (CT) and a reduced N practice with 225kgNha−1 (RN), two one-time UDP treatments: a current traditional practice under UDP (CTDP) and a reduced N practice under UDP (RNDP), and a CK treatment with no urea). The NH3 volatilization, grain yield and N use efficiency in terms of the N recovery efficiency (NRE) were investigated during the 2014–2016 rice growing seasons. Additionally, N diffusion and 15N-labeled urea experiments were conducted to explore the N release pattern and the fate of 15N under UDP. The results demonstrated that little NH4+-N could diffuse into surface water under UDP, thus, negligible floodwater NH4+-N was detected. The seasonally cumulative NH3 volatilization of the UDP accounted for only 1% of the total applied N, which decreased by 91% compared to surface broadcasting treatments. As a result, the NH3 intensity (NH3-N loss per crop yield) was reduced by 92% over surface broadcasting. Moreover, the deep placement of urea could supply a higher NH4+-N concentration in the soil during the early growth stage and prolong the duration of N availability for 2 months; as a result, UDP remarkably increased the N uptake by 28% compared with surface broadcasting treatments in the 3 years. The UDP treatments significantly increased the yield and NRE by 10% and 55% under favorable weather conditions (2015 and 2016 rice seasons), respectively. The RNDP treatment obtained the lowest N surplus (36kgNha−1), and the plant 15N uptake was 62% higher and the 15N loss was 38% lower with RNDP than surface broadcasting. Therefore, the deep placement of urea can be considered a slow release fertilizer, which better matches the N demand of rice plants and effectively minimizes N losses, especially NH3 volatilization. The RNDP treatment, with a 25% reduction in the N dose, can represent an effective and promising strategy to achieve environmental integrity and food security in intensive rice cropping systems.

Different effects of biochar and a nitrification inhibitor application on paddy soil denitrification: A field experiment over two consecutive rice-growing seasons

Biochar and nitrification inhibitors are increasingly being proposed as amendments to improve nitrogen use efficiency (NUE). However, their effects on soil denitrification and the major N loss in rice paddies over an entire rice-growing season are not well understood. In this study, using intact soil core incubation combined with N2/Ar technique, the impacts of biochar and a nitrification inhibitor (Ni), 2-chloro-6-(trichloromethyl)-pyridine, on rice yield and soil denitrification, as well as ammonia (NH3) volatilization, were investigated over two rice-growing seasons in the Taihu Lake region of China. Field experiments were designed with four treatments: N0 (no N applied), N270 (270kg N ha−1 applied), N270+C (25tha−1 biochar applied) and N270+Ni (2-chloro-6- [trichloromethyl] -pyridine, 1.35kgha−1N applied). Compared with single application of N fertilizer alone (N270), biochar (N270+C) and Ni (N270+Ni) applications increased rice yields by 4.2–5.2% and 6.2–7.3%, respectively. The cumulative N2-N and NH3-N losses in different treatments varied from 11.9 to 21.8% and from 11.5 to 22.0% of the applied N, respectively. Compared with the single application of N fertilizer, the Ni application increased total NH3 emission by 4.0–20.6% and significantly decreased total N2-N emission by 9.7–19.4% (p<0.05), while the biochar application increased total NH3 and N2-N emissions by 8.6–17.9% and 3.3–9.7%, respectively. Overall, the biochar application resulted in an 11–15% higher net gaseous N than the Ni application. Although the biochar application may increase the rice yield and consequently the plant N uptake, it also promoted N loss more than Ni. Therefore biochar may not be good for maintaining soil fertility over a long period. Instead, applying Ni may be an optimal practice to ensure food security, while decreasing gaseous N loss, for rice production in the Taihu Lake region of China.

Effects of Acidic Materials on the N Transformations During the Composting of Pig Manure and Wheat Straw

Understanding the effects of acidic materials on the N transformations becomes of critical importance to choose the additives with preserving nitrogen during the manure composting. A 40 d static composting experiment was conducted in the laboratory to explore the effects of acidic materials on changes of temperature, pH, EC (electrical conductivity), GI (germination index), N compounds and TOC (total organic carbon) during the composting of pig manure and wheat straw.Three acidic materials were selected as the additives, including phosphate fertilizer (P), rotten apples (A) and vinegar (V). The results showed that the duration with temperature higher than 50℃ in four treatments all exceeded ten days and reached the health standard of high temperature composting. The addition of phosphate fertilizer delayed the time of the pile entering into the high temperature stage, decreased the pH, and increased the EC during the whole composting. On a mass basis, 53.1%, 36.2%, 46.5% and 41.5% of original amount of N in CK, P, A and V were lost during the first 16 d, but there was still 20% N loss during 16-24 d in P and V treatments. The NH3-N loss accounted for 26.0%, 11.8%, 21.5% and 20.2% of the N loss. The addition of acidic materials effectively reduced the N loss and the emissions of NH3, and the phosphate fertilizer showed the best effect. In the end of composting, the GI all exceeded 80%, and met maturity requirements.

MANAGEMENT OF IRRIGATION AND NITROGEN FERTILIZERS TO REDUCE AMMONIA VOLATILIZATION

ABSTRACT Nitrogen losses by ammonia (NH3) volatilization can be reduced by appropriate irrigation management or by alternative N sources, replacing urea. The objective of this study was to evaluate the efficiency of irrigation management and N source combinations in decreasing NH3 volatilization from an Argissolo Vermelho Distrófico típico cultivated for 28 years with black oat (Avena strigosa) and maize (Zea mays), under no-tillage in the region of Depressão Central, Rio Grande do Sul, Brazil. The experiment was arranged in a randomized block design with split plots with three replications, where the main plots consisted of irrigation systems: no irrigation; irrigation immediately before and irrigation immediately after fertilization. The subplots were treated with different N sources: urea, urea with urease inhibitor and slow-release fertilizer, at an N rate of 180 kg ha-1, broadcast over maize, plus a control treatment without N fertilization. Ammonia volatilization was assessed using semi-open static collectors for 1, 2, 4, 6, and 10 days after N fertilization. In general, more than 90 % of total NH3-N losses occurred until three days after N fertilization, with peaks up to 15.4 kg ha-1 d-1. The irrigation was efficient to reduce NH3 losses only when applied after N fertilization. However, reductions varied according to the N fertilizer, and were higher for urea (67 %) and slightly lower for urea with urease inhibitor (50 %) and slow-release fertilizer (40 %), compared with the mean of the treatments without irrigation and irrigation before fertilization. The use of urea with urease inhibitor instead of urea was only promising under volatilization-favorable conditions (no irrigation or irrigation before N fertilization). Compared to urea, slow-release fertilizer did not reduce ammonia volatilization in any of the rainfed or irrigated treatments.

Isotope Ratio Mass Spectrometry Monitoring of Nitrogen Volatilization from Beef Cattle Feces and 15N-Labeled Synthetic Urine

A 15-day bench-scale manure storage experiment with a slurry mixture comprising beef cattle feces and synthetic urine with 15N-labeled urea was conducted to evaluate the source of volatilized ammonia nitrogen (NH3-N). Beef cattle feces was mixed daily in a 1:2.2 mass ratio with 15N-labeled urine and added for four consecutive days to 2-L storage containers and then left undisturbed for eleven days. Isotope ratio mass spectrometry was used to determine the origin of aerial NH3-N losses from the relative isotopic abundance of N in the 15N-labeled slurry mixture. On average 84% of total NH3-N losses originated from the urine portion and were highest during the first two to four days, when fresh material was added. After fresh material addition ceased, daily NH3-N emission from the urine decreased gradually, whereas emission from the feces remained relatively constant. Calculations showed that over 34% of aerial N was not captured, suggesting that other N gas emission is significant from slurry mixtures. Likely all uncaptured N losses were from urinary urea. The study verified the applicability of 15N-labeled synthetic urine for beef slurry mixtures. However, the results suggest further research to explain and model the NH3 and N release from fecal material is warranted and to determine the identity of the uncaptured N losses.

Assessing Tillage Systems for Reducing Ammonia Volatilization from Spring-Applied Slurry Manure

The effect of tillage management on NH3-N volatilization and its influence on succeeding corn (Zea mays L.) silage production were studied at the University of Massachusetts Agricultural Experiment Station (South Deerfield, MA) during 2010–2012 growing seasons. Tillage treatments consisted of disking before and after manure application, solid-tine aeration before and after manure application, and no-till management. The greatest NH3-N loss (61 percent) occurred within the first 8 h after slurry manure application regardless of tillage management. The greatest NH3-N emission occurred with surface application (no-till), which ranged between 5.2 and 10.3 kg NH3-N ha−1 (9–20 percent of NH3-N applied) over the 3 years of the study. Immediate incorporation of manure into soil through disking reduced NH3-N loss by 66 to 75 percent. Ammonia loss abatement with aeration before or after manure application ranged from 13 to 41 percent compared with surface manure application. Tillage management did not influence corn silage yield or quality.

Composting of solids separated from anaerobically digested animal manure: Effect of different bulking agents and mixing ratios on emissions of greenhouse gases and ammonia

We investigated the effects of bulking agents (BA) and mixing ratios on greenhouse gas (GHG) and NH3 emissions from composting digested solids (DS), separated from anaerobically digested manure and other bio-wastes, in small-scale laboratory composters. BA evaluated were plastic tube pieces (PT), woodchips (WC), bio-char (BC), barley straw (BS) and lupin residues (LR) and were included at a DS:BA of 3:1 or 6:1, resulting in nine treatments: CTDS (control, DS only), PT3:1, PT6:1, WC3:1, WC6:1, BC3:1, BC6:1, BS3:1 and LR3:1. Depending on treatment, C losses via CO2 and CH4 emissions accounted for 41.2–65.3 g C kg−1 initial total solids (TS) and 4.4–191.7 mg C kg−1 TS (8.4–16.1% and 0.001–0.05% of initial total-carbon), respectively, while N losses as N2O and NH3 emissions comprised 2.1–13.6 mg N kg−1 TS and 2.7–4.8 g N kg−1 TS (0.01–0.04% and 9.1–13.0% of initial total-nitrogen), respectively. Most of the CH4 emissions occurred during the thermophilic temperature phase, which had little or no effect on N2O emissions. BS addition to DS resulted in the lowest cumulative NH3-N and N2O-N losses. BC was as effective as BS in reducing cumulative NH3-N losses, but had non-significant effect on CH4-C emissions. Decreasing the mixing ratio from 6:1 to 3:1 reduced losses of CH4-C and N2O-N (except for BC) without any increase in NH3-N losses. BC and BS proved most effective in reducing emissions of total GHG (as CO2-equivalents). Composting of DS with C-rich BA can thus be an effective means of conserving N in DS, while also reducing GHG emissions.

Effects of Poultry Litter Injection on Ammonia Volatilization, Nitrogen Availability, and Nutrient Losses in Runoff

Poultry litter is a common organic amendment in agricultural production, but nutrient losses can reduce its effectiveness as a fertilizer. Three experiments were conducted to evaluate ammonia nitrogen (NH3-N) volatilization, N availability, and runoff losses of nutrients by conducting a closed chamber volatilization study, a soil incubation, and a rainfall simulation. In all studies, poultry litter was applied at a rate of 6.7 Mg · ha−1 either on the surface or injected and compared with an unamended control. In the volatilization and soil incubation studies, Braddock Loam and Bojac Sandy Loam surface soils were compared. Of the ammonium N added, cumulative loss of NH3-N by volatilization was 3% from injected and 121% from surface applied poultry litter after 7 days in the Loam. In the Sandy Loam, cumulative loss of NH3-N was 9% from injected and 153% from surface applied poultry litter after 7 days. After a 40-day soil incubation, injection increased total inorganic N by 52% and 99% for the Loam and Sandy Loam soils, respectively, when compared with surface application. Injection reduced total Kjeldahl N by 59%, total Kjeldahl P by 53%, dissolved reactive P, dissolved nitrate N by 73%, and dissolved NH3-N in runoff by 99%, compared with surface application. Injection reduced NH3-N volatilization and nutrients in runoff to levels of the control. These studies show that injection increases plant available N while decreasing losses through volatilization and runoff.

Nitrogen budget in a soil-plant system after brachiaria grass desiccation

Brachiaria spp. have been grown in a variety of cropping systems and are often terminated with herbicides, which may cause nitrogen (N) loss from the soil-plant system. In this study ammonia (NH3-N) loss by shoots and N balance in a soil-plant system were determined after desiccation of palisade grass (Brachiaria brizantha (Hochst. ex A. Rich) Stapf, cv. Marandu), signalgrass (Brachiaria decumbens Stapf), humidicola (Brachiaria humidicola (Rendle) Schweick) and Congo grass (Brachiaria ruziziensis Germain et Evrard). The grasses were grown in pots filled with an Oxisol in a greenhouse. Sixty days after planting, the plants were desiccated with glyphosate. Analyses were performed on plant and soil at desiccation and then at 7, 14, 21 and 28 days after desiccation in order to assess NH3-N losses by shoots and to estimate the N balance in the system. Total nitrogen (Total-N) concentration in shoots and roots of brachiarias decreased after desiccation, thereby reducing the amount of N in plants of the four brachiaria species. However, as most of the N lost by plants was released into the soil, N losses from the soil-plant system were small compared with the total N in the system: 1.2, 0.5, 0.4 and 1.4% for palisade grass, signalgrass, humidicola and Congo grass, respectively. N losses as NH3 from the soil-plant system after desiccation with glyphosate varied among brachiaria species, ranging from 0.8 to 2.0 g m−2 kg−1, and accounted for 30–80% of total loss.

Nitrogen mass balance in commercial roaster houses receiving different acidifier application rates

SUMMARY Broiler production has the potential to cause water and air pollution. Acidifiers such as sodium bisulfate (SBS) can reduce ammonia (NH3) emissions from broiler houses; NH3 is an important air pollutant that also affects bird health. Due to their longer grow-outs, roasters may require higher acidifier application rates to prevent unhealthy NH3 levels during the flock than ordinary broilers. Changes in NH3 emission with acidifier use may affect the partitioning of the input nitrogen (N) among the different N output pathways. Accounting for these output pathways through N mass balance provides a complete picture of N as it cycles through the roaster house. In a 2-yr study involving 9 flocks of roasters, 4 levels of SBS were applied to the litter in commercial roaster houses. Whereas the control treatment received up to 0.49 kg/ m 2 to the brood chamber, the high, medium, and low treatments received up to 1.46, 0.73, and 0.49 kg/m 2 , respectively, to the whole house. Ammonia-N emission decreased and N removed in cake and litter increased with SBS application rate. Nitrogen output components were averaged over the 4 treatments and expressed as percent of total N input or per unit mass of live weight (LW). Ammonia-N emission during grow-out, bird N exported, and cake and litter N removed accounted for 17.3% or 11.2 g/kg of LW, 38.9% or 25.1 g/kg of LW, and 22.4% or 14.4 g/kg of LW, respectively. We accounted for 79.1% of the total N inputs, with NH3-N losses during layout probably constituting the bulk of the unaccounted N. In addition to uncertainties in measurements of inputs and outputs, other factors that limited the ability to close the N mass balance were exclusion of feathers during cake and litter sampling, soil N leaching, and nitrous oxide emissions.

The chemical composition, fermentation profile, and microbial populations in tropical grass silages

The objective of this study was to evaluate the fermentation profile, chemical composition and microbial population and losses in the silages of signalgrass and Mombasa grass fertilized with the following levels of nitrogen (N): 0, 30, 60 and 90 kg/ha. The grasses were harvested at 70 days of regrowth, chopped and then ensiled in laboratory silos that had 20 kg of capacity and a snap-top cover and were fitted with Bunsen valves. Before ensiling, samples of the plants were used for the isolation and identification of lactic acid bacteria (LAB) in epiphytic microbiota. The design adopted was a 4 × 2 factorial arrangement, with four doses of N and two forage species, in a completely randomized design, with four replicates. The predominant species of LAB was Lactobacillus fermentum. The interaction between the N dose and forage species affected the dry matter (DM), crude protein (CP), neutral detergent fiber (NDF), acid detergent fiber (ADF) and water soluble carbohydrates (WSC) of the silages. The pH values and gas losses were influenced only by the forage species, with higher values for the Mombasa grass. For the ammonia (NH3-N) levels and effluent losses, there was an effect of the interaction between the forage species and N doses, and the highest values of NH3-N and effluent losses were found in the Mombasa grass silage fertilized with 60 kg N/ha. Nitrogen fertilization reduces the levels of DM and WSC in the silages and also increases the levels of CP, NH3-N and effluent losses.

Nitrogen metabolism and route of excretion in beef feedlot cattle fed barley-based backgrounding diets varying in protein concentration and rumen degradability1,2

The objectives of the study were to characterize the effects of CP concentration and ruminal degradability of barley-based backgrounding diets on route and chemical form of N excretion, ruminal fermentation, microbial protein synthesis, and nutrient digestion in beef cattle. Four Angus heifers (479 ± 14.6 kg average BW) with ruminal and duodenal cannulas were used in an experiment designed as a 4 × 4 Latin square. The basal diet consisted of 54% barley silage and 46% barley grain-based concentrate (DM basis). Dietary treatments included the basal diet with no added protein (12% CP) or diets formulated to contain 14% CP by supplementation with urea (UREA), urea and canola meal (UREA+CM), or urea, corn gluten meal, and xylose-treated soybean meal (UREA+CGM+xSBM). The amount of feed offered was restricted to 95% of ad libitum intake. There was no effect of the diets on DMI (P = 0.38), and therefore, N intake was less (P < 0.05) in heifers fed the 12% CP diets than the 14% CP diets. Fecal N output was not affected by the diet (P = 0.15), but urine N (P < 0.10) and urea N output were greater (P < 0.05) in heifers fed the 14% CP than the 12% CP diets. There was no effect of CP degradability (P > 0.10) on the amount of urine N output. Urine N output was 38.9 and 45.1 ± 5.50% of N intake in heifers fed the 12% CP and 14% CP diets (P < 0.05), respectively. Urea N, the form of N most susceptible to NH3-N volatilization and loss, was the major form of N in urine (75.5% in heifers fed the 12% CP diet and 81.4 ± 1.7% in heifers fed the 14% CP diets; P < 0.05). Supplemental RDP (UREA+CM) and RUP combined with urea (UREA+CGM+xSBM) to provide 14% CP increased (P < 0.05) ruminal NH3-N but had no effect on ruminal peptide N (P = 0.62) and free AA N (P = 0.18) concentration, the flow of microbial (P = 0.34) and feed (P = 0.55) N, and ruminal (starch, P = 0.11; NDF, P = 0.78) and total tract nutrient digestibility (OM, P = 0.21; starch, P = 0.16). Supplementation of barley-based backgrounding diets containing 12% CP with NPN alone or combined with ruminally degradable and undegradable true protein to attain 14% CP had no effect on fecal N output, but urine N and urea N increased irrespective of protein source. In addition, the ruminal degradability of the protein sources did not influence the composition of protein flowing to the intestine and site and extent of nutrient digestibility.

Mitigation of ammonia losses from urea applied to a pastoral system: The effect of nBTPT and timing and amount of irrigation

To investigate the effect of applying urea with or without the urease inhibitor (UI) N-(n-butyl) thiophosphoric triamide (nBTPT - trade name Agrotain®) and to assess impact of the amount and timing of irrigation on subsequent ammonia (NH3) emission, a field trial was set up on a research farm at Massey University, Palmerston North, New Zealand in December 2012. Measurements of the daily NH3 emission showed that majority of NH3 losses occurred during the first 1-3 days following urea application. Delaying irrigation for 48 hr post urea application resulted in high average NH3-N losses, at 23% and 28.3% for urea applied at 30 and 60 kg N ha-1, respectively. However, even when 5 or 10 mm of irrigation was applied 8 hours after urea application, average NH3 losses were still 11.3% and 14.4% of the N applied at 30 and 60 kg N ha-1, respectively. Our results suggest that 5 to 10 mm of irrigation/rainfall is needed very soon (

Ammonia losses estimated by an open collector from urea applied to sugarcane straw

The quantification of ammonia (NH3) losses from sugarcane straw fertilized with urea can be performed with collectors that recover the NH3 in acid-treated absorbers. Thus, the use of an open NH3 collector with a polytetrafluoroethylene (PTFE)-wrapped absorber is an interesting option since its cost is low, handling easy and microclimatic conditions irrelevant. The aim of this study was to evaluate the efficiency of an open collector for quantifying NH3-N volatilized from urea applied over the sugarcane straw. The experiment was carried out in a sugarcane field located near Piracicaba, São Paulo, Brazil. The NH3-N losses were estimated using a semi-open static collector calibrated with 15N (reference method) and an open collector with an absorber wrapped in PTFE film. Urea was applied to the soil surface in treatments corresponding to rates of 50, 100, 150 and 200 kg ha-1 N. Applying urea-N fertilizer on sugarcane straw resulted in losses NH3-N up to 24 % of the applied rate. The amount of volatile NH3-N measured in the open and the semi-open static collector did not differ. The effectiveness of the collection system varied non-linearly, with an average value of 58.4 % for the range of 100 to 200 kg ha-1 of urea-N. The open collector showed significant potential for use; however, further research is needed to verify the suitability of the proposed method.