NH3 Loss Research Articles

Why copper and zinc are ineffective in reducing soil urease activity in New Zealand dairy-grazed pasture soils

Micronutrients copper (Cu) and zinc (Zn) have the potential to inhibit soil urease activity (UA) and reduce ammonia (NH3) emissions over long duration (8–12 weeks) but have not been tested for reducing NH3 losses from cattle urine deposited in dairy-grazed pasture soils. The objective of this study was to assess the effectiveness and longevity of Cu and Zn in reducing soil UA, for the use of these metals to reduce NH3 emissions from deposited urine by grazing cattle. A series of experiments were conducted to (i) assess the relationship between inherent Cu and Zn status and soil UA of New Zealand dairy-grazed pasture soils, (ii) determine the impact of Cu and Zn addition to pasture soils on soil UA and (iii) investigate how soil organic carbon (C) and other C-related textural and mineralogical properties such as clay content and cation exchange capacity influence the effectiveness of added Cu and Zn in reducing urea hydrolysis. The results showed significant positive correlations of soil total C and total nitrogen (N) with soil UA. However, there were no significant negative correlations of soil UA with inherent Cu and Zn levels. Similarly, addition of Cu and Zn to soil did not significantly reduce soil UA. However, when Cu was added to two different soil supernatants there was a significant reduction in hydrolysis of urea applied at 120 and 600 mg urea-N kg–1 soil. Additions of Zn achieved negligible or small reductions in urea hydrolysis after 120 and 600 mg urea-N kg–1 soil applications to soil supernatants. This result suggests that Cu can inhibit soil UA and urea hydrolysis in soil supernatants with potentially low C, clay and cation exchangeable base contents. However, the interaction of bioavailable Cu with labile soil organic C and clay particles leads to its inactivation, resulting in ineffectiveness in organic C-rich pasture soils. Although most of the added Zn did not complex and remained bioavailable, the observed levels of bioavailable Zn had limited effect on soil UA.

Urea Hydrolysis and Calcium Carbonate Precipitation in Gypsum-Amended Broiler Litter.

Broiler () litter is subject to ammonia (NH) volatilization losses. Previous work has shown that the addition of gypsum to broiler litter can increase nitrogen mineralization and decrease NH losses due to a decrease in pH, but the mechanisms responsible for these effects are not well understood. Therefore, three laboratory studies were conducted to evaluate the effect of gypsum addition to broiler litter on (i) urease activity at three water contents, (ii) calcium carbonate precipitation, and (iii) pH. The addition of gypsum to broiler litter increased ammonium concentrations ( < 0.0033) and decreased litter pH by 0.43 to 0.49 pH units after 5 d ( < 0.0001); however, the rate of urea hydrolysis in treated litter only increased on Day 0 for broiler litter with low (0.29 g HO g) and high (0.69 g HO g) water contents, and on Day 3 for litter with medium (0.40 g HO g) water content ( < 0.05). Amending broiler litter with gypsum also caused an immediate decrease in litter pH (0.22 pH units) due to the precipitation of calcium carbonate (CaCO) from gypsum-derived calcium and litter bicarbonate. Furthermore, as urea was hydrolyzed, more urea-derived carbon precipitated as CaCO in gypsum-treated litter than in untreated litter ( < 0.001). These results indicate that amending broiler litter with gypsum favors the precipitation of CaCO, which buffers against increases in litter pH that are known to facilitate NH volatilization.

Azolla biofertilizer for improving low nitrogen use efficiency in an intensive rice cropping system

The efficient use of nitrogen (N) in crop production is critical for meeting the challenges of food security and environmental integrity. Azolla biofertilizer may be a promising approach to achieve better N use efficiency (NUE) in paddy rice fields due to its great potential for biological N fixation (BNF). The objective of this study was to determine the efficacy of partially substituting Azolla biofertilizer for synthetic N fertilizer to improve NUE, reduce N loss and enhance rice yield in the currently highly fertilized rice cropping systems of China. Therefore, a 3-year field experiment was conducted with five treatments: CK (control without urea), FN (farmers’ N practice), FNA (the farmers’ N combined with Azolla biofertilizer), RN (reducing farmers’ N by 25%) and RNA (substituting Azolla biofertilizer for 25% farmers’ N). The NUE, ammonia (NH3) volatilization, rice yield and net economic benefit (the difference between the value of the harvest grain and the costs of fertilizer and Azolla inputs) were assessed. The results showed that in the RNA and FNA treatments, Azolla biofertilizer produced higher recovery efficiency of fertilizer N by 69% and 59%, provided higher agronomic N use efficiency by 52% and 31% and achieved higher partial factor productivity of applied N by 43% and 13% than FN for the 3 years, respectively. In addition, the RNA and FNA treatments achieved crop 15N recovery that was 64% and 49% higher than the FN treatment, respectively. The improved NUE under the Azolla biofertilizer treatments were attributed to reduced N loss and enhanced N uptake by rice plants. The RNA and FNA treatments significantly reduced 15N loss by 48% and 26%, as well as lowered NH3 loss by 42% and 12% over FN, respectively. In addition, Azolla could fix 52 and 44kgNha−1 crop−1 in the RNA and FNA treatments, and thereby, Azolla biofertilizer resulted in higher N uptake that was 17% and 33% higher in the RNA and FNA groups than in FN, respectively. As a result, the RNA and FNA treatments achieved higher rice yield by 8% and 14% over FN, respectively, but they attained similar and higher net economic benefit over FN for the 3 years. Therefore, substituting Azolla biofertilizer for 25% of urea-N provides a financially attractive option for farmers to substantially improve NUE and yield and effectively reduce N loss in intensive rice cropping systems.

A Study on Growth Performance of Ducks Fed Diets with Different Types of Sipjeondaebo-Tang Byproduct Meal and Red Ginseng Marc with Fermented Red Koji and Ammonia Fluxes in Duck Litter using Alum or Aluminum Chloride.

The aims of the present study were to investigate the growth performance of ducks fed diets with different types of Sipjeondaebo-tang (ST) byproduct meal and red ginseng marc with fermented red koji (RGMK), and to investigate ammonia (NH3) fluxes from duck litter treated with alum or aluminum chloride (AlCl3). A total of 270 1-d-old ducks (180 males and 90 females) were allotted in a completely randomized design with 6 treatments and 3 replicates of 15 birds per pen. The six diet treatments were: basal diet, pelleted 1% ST byproduct powder, pelleted 1% RGMK, 1% blends (a mixture of ST byproduct and RGMK) powder, 1% pelleted blends, and coated pellets of 1% blends. The six litter treatments with 6 diet treatments were: no treatment, 50, 100, or 200 g alum/kg duck litter, and 100 g or 200 g AlCl3/kg duck litter (treatments T1, T2, T3, T4, and T5, respectively). During days 10 to 40, ducks fed the 5 experimental diets had significantly different (p<0.05) weight gains and feed conversion ratios compared with those fed the control diet, but initial body weight, final body weight, feed intake, and mortality were not affected. There were significant differences (p<0.05) in NH3 fluxes among treatments over the 6 weeks of the study, except for week 0. The relative NH3 losses at week 6 were lower by 25.6, 45.3, 45.6, 46.7, and 48.6% than those in the controls in T1, T2, T3, T4, and T5 respectively. In conclusion, feeding pellets or coated pellets of ST and RGMK and using alum or AlCl3 in the litter at the same time improves weight gain and feed conversion ratio performance and reduces mortality and NH3 losses in ducks.

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.

Ammonia Volatilization from Broadcast Urea and Alternative Dry Nitrogen Fertilizers

Core Ideas Volatile NH3 loss in the field was quantified via the modified passive flux method. Urease inhibitor (NBPT) or S‐coated urea reduced N loss by 39 to 53% versus urea. Urea plus ammonium sulfate (Urea‐AS) reduced N loss by 19 to 28% versus urea. A companion laboratory trial found the same relative efficacy among fertilizers. Substantial ammonia (NH3) loss can occur when urea is broadcast without incorporation. Choosing an alternate fertilizer (instead of urea) is one option when incorporation of urea by tillage or sprinkler irrigation is not feasible. This research evaluated alternative N fertilizer products (vs. urea) using the modified passive flux method. Fertilizers were broadcast (168 kg N ha–1) on an Irrigon fine sandy loam soil (mesic Xeric Haplocambid), and not incorporated. Light showers (7 mm in 14 d after application) triggered NH3 loss. After 34 d, ammonia‐N loss was 14 to 17% of N applied as ammonium sulfate (AS) or ASN (fused granule of ammonium sulfate and ammonium nitrate), 22% as S‐coated urea (SCU), 28% as urea + urease inhibitor NBPT [N‐(n‐butyl) thiophosphoric triamide], and 33 to 37% as blended or fused urea‐AS fertilizers (79:21 urea/ammonium sulfate, w/w) vs. 46% as urea. A companion 44‐d laboratory study (16°C) demonstrated a similar ranking of fertilizer efficacy. We conclude that fusing AS with urea in a granule (instead of blending) did not reduce NH3 loss. Partial substitution of AN for AS in a fused granule (ASN) did not provide additional benefit in reducing NH3 loss vs. AS alone. Treated urea products (SCU and urea + NBPT) had greatest efficacy in reducing NH3 loss during the first 10 d after application, with reduced efficacy thereafter, likely due to the degradation of the coating (SCU) or the urease inhibitor NBPT.

Direct and indirect greenhouse gas emissions from two intensive vegetable farms applied with a nitrification inhibitor

Nitrification inhibitors are effective in decreasing direct nitrous oxide (N2O) emission from agricultural soils but may stimulate ammonia (NH3) volatilization. Part of the NH3 deposited to land is converted to N2O and emitted to the atmosphere, termed indirect N2O emission. While vegetable production systems entail a considerable risk of NH3 and N2O loss from high nitrogen (N) input to the soil, the simultaneous effects of nitrification inhibitors on these N loss pathways have rarely been examined. We conducted paddock-scale (ca. four hectares) measurements using micrometeorological techniques to simultaneously quantify the effects of a nitrification inhibitor DMPP (3,4-dimethylpyrazole phosphate) on NH3 and N2O emissions from two intensive vegetable farms. We found that DMPP decreased direct N2O emission by 37–38% (2.2–7.3 kg N ha−1) across the farms during the most intensive period of N input (18 days), but could increase NH3 volatilization by 3–39% (1.6–4.8 kg N ha−1). The results highlight the importance of considering multiple N loss pathways when developing a strategy for mitigating agricultural greenhouse gas emissions.

Potential short-term losses of N&amp;lt;sub&amp;gt;2&amp;lt;/sub&amp;gt;O and N&amp;lt;sub&amp;gt;2&amp;lt;/sub&amp;gt; from high concentrations of biogas digestate in arable soils

Abstract. Biogas digestate (BD) is increasingly used as organic fertilizer, but has a high potential for NH3 losses. Its proposed injection into soils as a countermeasure has been suggested to promote the generation of N2O, leading to a potential trade-off. Furthermore, the effect of high nutrient concentrations on N2 losses as they may appear after injection of BD into soil has not yet been evaluated. Hence, we performed an incubation experiment with soil cores in a helium–oxygen atmosphere to examine the influence of soil substrate (loamy sand, clayey silt), water-filled pore space (WFPS; 35, 55, 75 %) and application rate (0, 17.6 and 35.2 mL BD per soil core, 250 cm3) on the emission of N2O, N2 and CO2 after the usage of high loads of BD. To determine the potential capacity for gaseous losses, we applied anaerobic conditions by purging with helium for the last 24 h of incubation. Immediate N2O and N2 emissions as well as the N2 ∕ (N2O+N2) product ratio depended on soil type and increased with WFPS, indicating a crucial role of soil gas diffusivity for the formation and emission of nitrogenous gases in agricultural soils. However, emissions did not increase with the application rate of BD. This is probably due to an inhibitory effect of the high NH4+ content of BD on nitrification. Our results suggest a larger potential for N2O formation immediately following BD injection in the fine-textured clayey silt compared to the coarse loamy sand. By contrast, the loamy sand showed a higher potential for N2 production under anaerobic conditions. Our results suggest that short-term N losses of N2O and N2 after injection may be higher than probable losses of NH3 following surface application of BD.

Duckweed (Spirodela polyrhiza) as green manure for increasing yield and reducing nitrogen loss in rice production

Increasing rice production to feed the world’s growing population while protecting the environment requires more optimal use of fertilizers. In China, the current high input, high output and high reliance on synthetic nitrogen (N) fertilizer in agriculture has resulted in high N losses, especially ammonia (NH3) emission. Urea combined with green manure (GM) might be a promising approach to improve N fertilizer management. However, few studies have evaluated duckweed in this manner. Duckweed does not require arable land for cultivation and thus avoids competition with food crops. Therefore, a field experiment was conducted for three years with five treatments (CK, no N-fertilizer; CT, conventional practice, urea alone at 300kgNha−1; CTD, urea combined with duckweed at 300kgNha−1; RN, urea alone at 225kgNha−1; and RND, urea combined with duckweed at 225kgNha−1) in an intensive rice cropping system in the Taihu Region of China. The results for two years showed that urea combined with duckweed cover reduced NH3 loss by 36–52% over CT. This reduction was attributed primarily to the formation of a physical barrier and the uptake of NH4+ by duckweed. The 15N recovery for 15N balance conducted for one year was 38% higher and the 15N loss was 16% lower for CTD than that of CT. Furthermore, urea combined with duckweed increased N accumulation in the aboveground plants by 14–25% over CT for the 3 years. As a result, urea combined with duckweed achieved higher rice yield by 9–10%, and higher net economic benefit by 10–11% over CT for the 3 years; however, using the conventional rate of 300kgNha−1 did not increase rice yield over using the reduced N rate of 225kgNha−1, with or without duckweed. Thus, duckweed as GM combined with chemical fertilizer application provided an approach for increasing the rice yield without increasing inputs of N fertilizer and thereby provided a financially attractive option for farmers to achieve environmental integrity and ensure food security in rice production.

Wheat Production, Nitrogen Transformation, and Nitrogen Losses as Affected by Nitrification and Double Inhibitors

Core Ideas The environmental and agronomic benefits of amending urea with inhibitors was evaluated. Double inhibitor significantly reduced all three major N losses compared with urea. Nitrification inhibitor did not reduce NH3 volatilization. Higher N2O fluxes were observed at 35 to 60% WFPS, soil temperature &gt;10°C, and NO3− contents &gt;5 mg kg−1 dry soil. Nitrification inhibitor/double inhibitors maintained spring wheat grain and protein yields. Enhanced efficiency fertilizers have the potential to reduce N losses from urea (U)‐fertilized soils. A field study was conducted during 2015 and 2016 at Glyndon, MN, under rainfed spring wheat (Triticum aestivum L.) to assess the effectiveness of U with/without nitrification inhibitor (NI) or both urease and nitrification inhibitors (DI) to reduce N losses and improve crop yields. Treatments consisted of three N sources (U, NI, and DI) applied at two N rates (146 and 168 kg N ha−1) along with the control. In 2015, DI significantly reduced ammonia (NH3) volatilization by 34% and nitrous oxide (N2O) emissions by 43% as compared with U (7.78 kg NH3–N ha−1, 2.24 kg N2O‐N ha−1). Similarly, NI (9.85 kg NH3–N ha−1, 1.05 kg N2O‐N ha−1) significantly reduced N2O emissions by 53%, but had similar NH3 loss to that of U. The DI significantly reduced NH3 loss by 48% compared with NI. Higher N2O fluxes were observed when WFPS (water‐filled pore space) lies between 35 and 60%, soil temperature &gt;10 to 12°C, and soil NO3− contents &gt;5 mg kg−1. Urea with NI or DI also reduced soil water nitrate (NO3−) concentrations below the rooting zone. The grain and protein yields were similar among U, NI, and DI treatments. These results suggest that the combined application of both urease and nitrification inhibitors could be an effective means to reduce all possible N losses from urea‐fertilized soils, while maintaining crop yields in rainfed spring wheat system.

Nitrogen release from urea with different coatings.

Coatings or urease inhibitors are designed to reduce losses of ammonia [NH3(g) ] from urea fertilizers. However, nitrogen (N) release and its effects on soil solution have not previously been evaluated under standardized conditions in soils. In this study, the urea fertilizers were incubated in chambers filled with sandy loam soil, adapted for the collection of NH3(g) and soil solution by centrifugation. In the fast-release N fertilizers, around 93% and 100% of urea-N applied was recovered within the first hours of incubation. In contrast, in the slow-release N fertilizers, less than 40% of urea-N applied, was recovered at 19 days of incubation. The maximum N release from the fertilizers followed the order: UP1 (106%) ≈ UNBPT (102%) ≈ urea (93%) > USP2 (57%) ≈ USP3 (57%) > USP4 (31%) ≈ USP5 (18%). NH3(g) volatilization accounted for only 3% of the applied N in the slow-release fertilizers, which corresponded to about 88% less than the NH3(g) loss from prilled urea. This study demonstrated distinct N release patterns, which changed the N dynamics in the soil. Some coatings effectively delayed urea release from granules and reduced NH3(g) gas losses, while other were not efficient. © 2017 Society of Chemical Industry.

Nitrification inhibitors mitigated reactive gaseous nitrogen intensity in intensive vegetable soils from China

Nitrification inhibitors, a promising tool for reducing nitrous oxide (N2O) losses and promoting nitrogen use efficiency by slowing nitrification, have gained extensive attention worldwide. However, there have been few attempts to explore the broad responses of multiple reactive gaseous nitrogen emissions of N2O, nitric oxide (NO) and ammonia (NH3) and vegetable yield to nitrification inhibitor applications across intensive vegetable soils in China. A greenhouse pot experiment with five consecutive vegetable crops was performed to assess the efficacies of two nitrification inhibitors, namely, nitrapyrin and dicyandiamide on reactive gaseous nitrogen emissions, vegetable yield and reactive gaseous nitrogen intensity in four typical vegetable soils representing the intensive vegetable cropping systems across mainland China: an Acrisol from Hunan Province, an Anthrosol from Shanxi Province, a Cambisol from Shandong Province and a Phaeozem from Heilongjiang Province. The results showed soil type had significant influences on reactive gaseous nitrogen intensity, with reactive gaseous nitrogen emissions and yield mainly driven by soil factors: pH, nitrate, C:N ratio, cation exchange capacity and microbial biomass carbon. The highest reactive gaseous nitrogen emissions and reactive gaseous nitrogen intensity were in Acrisol while the highest vegetable yield occurred in Phaeozem. Nitrification inhibitor applications decreased N2O and NO emissions by 1.8–61.0% and 0.8–79.5%, respectively, but promoted NH3 volatilization by 3.2–44.6% across all soils. Furthermore, significant positive correlations were observed between inhibited N2O+NO and stimulated NH3 emissions with nitrification inhibitor additions across all soils, indicating that reduced nitrification posed the threat of NH3 losses. Additionally, reactive gaseous nitrogen intensity was significantly reduced in the Anthrosol and Cambisol due to the reduced reactive gaseous nitrogen emissions and increased yield, respectively. Our findings highlight the benefits of nitrification inhibitors for integrating environment and agronomy in intensive vegetable ecosystems in China.

Environmental niches and metabolic diversity in Neoarchean lakes.

The diversification of macro-organisms over the last 500 million years often coincided with the development of new environmental niches. Microbial diversification over the last 4 billion years likely followed similar patterns. However, linkages between environmental settings and microbial ecology have so far not been described from the ancient rock record. In this study, we investigated carbon, nitrogen, and molybdenum isotopes, and iron speciation in five non-marine stratigraphic units of the Neoarchean Fortescue Group, Western Australia, that are similar in age (2.78-2.72Ga) but differ in their hydro-geologic setting. Our data suggest that the felsic-dominated and hydrologically open lakes of the Bellary and Hardey formations were probably dominated by methanogenesis (δ13 Corg =-38.7±4.2‰) and biologic N2 fixation (δ15 Nbulk =-0.6±1.0‰), whereas the Mt. Roe, Tumbiana and Kylena Formations, with more mafic siliciclastic sediments, preserve evidence of methanotrophy (δ13 Corg as low as -57.4‰, δ13 Ccarb as low as -9.2‰) and NH3 loss under alkaline conditions. Evidence of oxygenic photosynthesis is recorded only in the closed evaporitic Tumbiana lakes marked by abundant stromatolites, limited evidence of Fe and S cycling, fractionated Mo isotopes (δ98/95 Mo=+0.4±0.4‰), and the widest range in δ13 Corg (-57‰ to -15‰), suggesting oxidative processes and multiple carbon fixation pathways. Methanotrophy in the three mafic settings was probably coupled to a combination of oxidants, including O2 and SO42- . Overall, our results may indicate that early microbial evolution on the Precambrian Earth was in part influenced by geological parameters. We speculate that expanding habitats, such as those linked to continental growth, may have been an important factor in the evolution of life.

Optimizing urease inhibitor usage to reduce ammonia emission following urea application over crop residues

Abstract Nitrogen loss as ammonia (NH3) is a major problem when urea is topdressed over crop residues. The treatment of urea with N-(n-butyl) thiophosphoric triamide (NBPT) temporarily inhibits urease activity and reduces NH3 volatilization loss under many agro­ecological conditions. However, the amount of straw on the soil in green sugarcane trash blanketing (GCTB) systems affects the success of NBPT in reducing NH3 loss. We hypothesized that an increase in the NBPT concentration in urea above the current level (530 mg NBPT kg−1 urea) in Brazil is necessary to reduce the NH3 volatilization and to improve the efficiency of urea in GCTB systems. We evaluated the NH3 loss from urea treated with NBPT under field conditions in GCTB systems. Six field trials were conducted across the State of Sao Paulo, the main sugarcane-growing region in Brazil. The treatments were urea, ammonium nitrate, urea treated with NBPT at concentrations of 530, 850, 1500, and 2000 mg kg−1, and a control plot without N fertilizer. The amount of volatized NH3 was assessed through a closed semi-static collector containing two acid-trap foam disks, and analyzed by colorimetry using flow injection analysis. NBPT concentrations above 530 mg kg−1 delayed the time of maximum rate of loss and also reduced cumulative NH3 loss. Ammonia emissions were linearly reduced with increasing NBPT concentrations until 1000 mg kg−1. Any further increase in the NBPT concentration did not result in a substantial reduction of NH3 volatilization. Increasing the NBPT concentration in urea is an effective approach to optimize the adoption of urea-based fertilizers in tropical GCTB systems.

Characterizing ammonia emissions from horses fed different crude protein concentrations.

Evaluating impact of animal agriculture on air quality has been the focus of recent research. Ammonia (NH) volatilization occurs when undigested protein in feces and urea in urine is broken down by bacteria and enzymes. Information regarding NH emission from equine facilities is limited, and effects of CP intake on NH emissions have not been investigated. Nine mature geldings were used in a 3 × 3 replicated Latin square design study to determine effects of dietary CP on potential NH losses from feces and urine. We hypothesized feeding horses above the CP requirement would result in an increase in NH emissions from urine and feces and different bedding materials would affect NH emissions from urine. Diets were formulated using different ratios of bahiagrass () and Tifton-85 bermudagrass () hays, and a commercial vitamin mineral supplement to provide 3 different CP concentrations and labeled in relation to each other: LOW-CP, MED-CP, and HIGH-CP (10.6%, 11.5%, and 12%, respectively). Each study period consisted of an 11-d diet adaptation phase, followed by a 3-d total collection of urine and feces. To determine total nitrogen (TN) and urea-N concentrations, samples were pooled by period ( = 9). For in vitro determination of NH concentrations, urine and fecal samples were pooled within period by diet ( = 3) and mixed with either wheat straw or wood shavings. Ammonia emission of these samples was measured using a vessel system with an airflow rate (2.5 L/min) at 20°C over a 7-d period. Concentration of NH in each vessel was measured using a photoacoustic multigas analyzer. Temperature, airflow rate, and NH concentration in each vessel were used to calculate NH emission rate (ER). Data were analyzed using a mixed model ANOVA with repeated measures. Urinary TN and urea-N excretion increased as CP intake increased ( < 0.0001). Vessel urinary NH concentrations were not different across diets ( = 0.1225), ranging from 55.48 ppm (LOW-CP) to 101.14 ppm (HIGH-CP); however, they differed between bedding types ( < 0.0001), with straw higher than shavings (97 vs. 73.5 ppm, respectively). Cumulative urinary NH ER tended to be different across diets ( = 0.0550) ranging from 5.87 g/m to 9.97 g/m and bedding types ( = 0.0129), with straw being higher than shavings (11.1 vs. 6.9 g/m, respectively). Overfeeding CP to horses can lead to increased urinary TN and urea-N excretion, which could lead to greater of NH in the atmosphere.

Ammonia and greenhouse gases losses from mechanically turned cattle manure windrows: A regional composting network

An on-farm composting network operates in the Basque Country (northern Spain), in which solid manure produced in livestock farms (mostly dairy and beef cattle) is composted through windrow turning. This network aims to produce a valuable resource (compost) for the farmers whereas the volume of the solid manure was reduced at farm level The objective of the study was to assess the gaseous losses (NH3 and GHG) from 6 on-farm composting windrows (either deep litter systems or solid fraction after slurry separation) after turning operations. Monitored turning events occurred 1 to 4 months after establishing the heaps on the field. Ammonia and greenhouse gas (GHG) losses were estimated by the open and close chamber techniques, respectively. Results showed overall low emission rates related to the long degradation period of the windrows. Maximum NH3 release was at 2.0 mg m−2 d−1 after the second/third turning events. Baseline N2O losses were below 50 mg m−2 d−1, with maximum rates close to 500 mg m−2 d−1 some days after turning works. Methane emissions were mostly below 100 mg m−2 d−1, while CO2 losses were lower than 25 g m−2 d−1. Carbon dioxide peaks (≈250 g m−2 d−1) were reached after the second/third turnings. Overall, gaseous N and C losses accounted for 0.1 and 1% of the initial N and C content of the windrows, respectively. The present study concluded that two/three turning operations in aged solid manure-derived compost windrows do not have significant effects on NH3 and GHG losses. The magnitude of the gaseous losses from on-farm composting systems is dependent on the manure management practices at farm level (e.g. moment of windrow stacking).

Gaseous emissions and modification of slurry composition during storage and after field application: Effect of slurry additives and mechanical separation

The aim of the study was to evaluate the impact of slurry treatment by additives (EU200® (EU200), Bio-buster® (BB), JASS® and sulphuric acid (H2SO4)) and mechanical separation on the physical-chemical characteristics, gaseous emissions (NH3, CH4, CO2 and N2O) during anaerobic storage at ∼20 °C (experiment 1) and NH3 losses after field application (experiment 2). The treatments studied in experiment 1 were: whole slurry (WS), WS+H2SO4 to a pH of 6.0, WS+EU200 and WS+BB. Treatments for experiment 2 were: WS, slurry liquid fraction (LF), composted solid fraction (CSF), LFs treated with BB (LFB), JASS® (LFJ), H2SO4 to a pH of 5.5 (LFA) and soil only (control). The results showed an inhibition of the degradation of organic materials (cellulose, hemicellulose, dry matter organic matter and total carbon) in the WS+H2SO4 relative to the WS. When compared to the WS, the WS+H2SO4 increased electrical conductivity, ammonium (NH4+) and sulphur (S) concentrations whilst reducing slurry pH after storage. The WS+H2SO4 reduced NH3 volatilization by 69% relative to the WS but had no effect on emissions of CH4, CO2 and N2O during storage. Biological additive treatments (WS+EU200 and WS+BB) had no impact on slurry characteristics and gaseous emissions relative to the WS during storage. After field application, the cumulative NH3 lost in the LF was almost 50% lower than the WS. The losses in the LFA were reduced by 92% relative to the LF. The LFB and LFJ had no impact on NH3 losses relative to the LF. A significant effect of treatment on NH4+ concentration was found at the top soil layer (0–5 cm) after NH3 measurements with higher concentrations in the LF treatments relative to the WS. Overall, the use of the above biological additives to decrease pollutant gases and to modify slurry characteristics are questionable. Reducing slurry dry matter through mechanical separation can mitigate NH3 losses after field application. Slurry acidification can increase the fertilizer value (NH4+ and S) of slurry whilst mitigating the environmental impacts through a decrease in NH3 losses during storage and after application.

Composição química de silagem e feno de Gliricídia sepium em diferentes alturas de resíduo

RESUMO Objetivou-se avaliar a qualidade química de silagem e feno de gliricídia em diferentes alturas de resíduo. Utilizou-se delineamento experimental em blocos ao acaso em esquema fatorial (3×2), constando de três alturas de resíduo (70, 90 e 110 cm) e dois procedimentos de conservação de forragem (silagem e fenação) com quatro repetições. Para os valores de pH da gliricídia in natura e silagem não diferiram em relação à altura de resíduo, diferente dos teores de nitrogênio amoniacal (N-NH3), onde na altura de 70 cm, apresentaram menores valores. As alturas de corte não influenciaram as perdas por gases, efluentes e recuperação da matéria seca da silagem de gliricídia. O feno apresentou maiores teores de proteína bruta (PB). O menor valor de matéria seca (MS) a 70 cm para o feno, conferiu-lhe menor acúmulo de massa seca, apresentando ainda, valores superiores de extrato etéreo (EE) e fibra detergente neutro (FDN) em relação à silagem para as alturas de 70 e 90 cm. A planta mantida em altura mais elevada (110 cm), acumulou maior EE e concentração de material fibroso. A silagem de gliricídia apresenta valores adequados de pH independente da altura residual, assim como não influenciam as perdas fermentativas da silagem, no entanto, há perdas elevada de N-NH3 para altura residual 110 cm. MS, EE e FDN sofrem influência das alturas de resíduos, assim como pelos métodos de conservação.

Nitrogen losses to the environment following food-based digestate and compost applications to agricultural land

The anaerobic digestion of food waste for energy recovery produces a nutrient-rich digestate which is a valuable source of crop available nitrogen (N). As with any ‘new’ material being recycled to agricultural land it is important to develop best management practices that maximise crop available N supply, whilst minimising emissions to the environment. In this study, ammonia (NH3) and nitrous oxide (N2O) emissions to air and nitrate (NO3−) leaching losses to water following digestate, compost and livestock manure applications to agricultural land were measured at 3 sites in England and Wales. Ammonia emissions were greater from applications of food-based digestate (c.40% of total N applied) than from livestock slurry (c.30% of total N applied) due to its higher ammonium-N content (mean 5.6 kg/t compared with 1–2 kg/t for slurry) and elevated pH (mean 8.3 compared with 7.7 for slurry). Whilst bandspreading was effective at reducing NH3 emissions from slurry compared with surface broadcasting it was not found to be an effective mitigation option for food-based digestate in this study. The majority of the NH3 losses occurred within 6 h of spreading highlighting the importance of rapid soil incorporation as a method for reducing NH3 emissions. Nitrous oxide losses from food-based digestates were low, with emission factors all less than the IPCC default value of 1% (mean 0.45 ± 0.15%). Overwinter NO3− leaching losses from food-based digestate were similar to those from pig slurry, but much greater than from pig farmyard manure or compost. Both gaseous N losses and NO3− leaching from green and green/food composts were low, indicating that, in these terms, compost can be considered as an ‘environmentally benign’ material. These findings have been used in the development of best practice guidelines which provide a framework for the responsible use of digestates and composts in agriculture.

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.