Reduced NH3 Loss Research Articles

Effects of enhanced efficiency nitrogen fertilizers on NH3 losses in a calcareous fluvo-aquic soil: a laboratory study

Excessive ammonia (NH3) emission to the atmosphere can cause a series of environmental problems and further cost to human health. Enhanced efficiency nitrogen (N) fertilizers (EENFs) were designed to reduce N losses to the environment and thus to improve fertilizer N use efficiency. The aim of the present study was to test the effectiveness of EENFs on NH3 emissions from surface-broadcast urea (dominant N application method for the studied region) in a fluvo-aquic soil under laboratory conditions. The study consisted of five treatments: (1) UREA: common urea; (2) UREA + NP: urea with incorporated nitrification inhibitor nitrapyrin; (3) UREA + DCD: urea with incorporated nitrification inhibitor dicyandiamide; (4) UREA + NBPT: urea with incorporated urease inhibitor NBPT [N-(n-butyl) thiophosphoric triamide]; (5) PCU, a polymer-coated urea. Urea with or without NP, DCD, and NBPT was dissolved in deionized water and was then carefully broadcast to the soil surface. The polymer-coated urea was surface-broadcast uniformly, and thereafter, deionized water was carefully dripped onto the soil surface. A forced-draft system with a volatilization chamber was employed to measure the NH3 flux. After the main experiment, the upper and lower soil layer was separately homogenized for analysis of soil ammonium N (NH4+-N) and nitrate N (NO3−-N) contents. The NH3 flux peak for UREA + NP, UREA + DCD, and UREA + NBPT treatment occurred on 5–8 days after fertilizer application, which were 1.04, 1.16, and 0.36 μg N cm−2 h−1, respectively, while NH3 flux for PCU treatment was very low (0.02–0.19 μg N cm−2 h−1) and no obvious NH3 flux peak emerged during the whole experiment. Urea with incorporated NP and DCD increased cumulative NH3 losses by 59% and 202% compared to urea only, respectively, while urea incorporated with NBPT and PCU reduced cumulative NH3 losses by 59% and 82% compared to urea only, respectively, Our results suggested that NH3 losses were greatly increased by applying the nitrification inhibitors nitrapyrin and dicyandiamide to urea, and nitrification inhibitors need to be carefully used in the fluvo-aquic soil. As surface-broadcast urea is nowadays still the dominant N application method in the NCP, surface application of NBPT-amended urea or PCU would be good options to reduce NH3 losses without having to change farmers’ fertilizer application method.

Use of a urease inhibitor to mitigate ammonia emissions from urine patches

ABSTRACT Urine deposition by grazing livestock is the single largest source of ammonia (NH3) volatilisation losses in New Zealand. Urease inhibitors (UI) have been used to mitigate NH3 losses from fertiliser urea and animal urine. In previous trials, the UI effect in reducing NH3 emissions from urine has been measured by applying urine mixed with the UI to the pasture soil thus increasing the chances of better interaction of the UI in inhibiting the urease enzyme. However, these trials do not represent a realistic grazing scenario where only urine is deposited onto the soil. This current research aimed to identify the best time to spray nBTPT (a UI containing 0.025% N-(n-butyl) thiophosphoric triamide) onto pasture soil to reduce NH3 losses from urine patches. The treatments were: a control (without urine and nBTPT), urine alone at 530 kg N ha–1 and urine plus nBTPT. The UI was applied to the chambers and soil plots 5 and 3 days prior to urine deposition, on the same day and 1, 3 and 5 after urine deposition in autumn. Ammonia losses were measured using the dynamic chamber method. The application of the inhibitor prior to urine deposition reduced NH3 losses with reductions of 27.6% and 17.5% achieved for UAgr-5 and UAgr-3, respectively. However, reductions in NH3 emission were 0.6–2.9% for inhibitor applied post urine deposition. There was also a reduction in both soil NH4 +–N concentration and soil pH in comparison with urine alone or with the treatments where nBTPT was applied after urine deposition.

Influence of Dairy Slurry Manure Application Method, Fall Application‐Timing, and Winter Rye Management on Nitrogen Conservation

Core Ideas Manure application method and timing affected ryelage but not rye cover biomass. Manure injection compared to broadcast conserved manure‐N in ryelage. Manure injection compared to broadcast with rye cover resulted in more corn silage. Late injection compared to early injection conserved more manure‐N in ryelage. Late versus early injection resulted in more manure‐N in soil and more corn after cover crops. Fall manure applications can lead to nutrient losses prior to spring planting. This 2‐yr study evaluated effects of winter cereal rye (Secale cereal L.) crop management (cover crop versus ryelage), and fall, dairy slurry manure application method (broadcasted versus injected) and timing (September vs. November) on manure–N conservation. Nitrogen conservation was calculated from NH3 volatilization, percentage of manure–N in aboveground rye (%ManureN‐R) and soil (%ManureN‐S) in spring prior to corn (Zea mays L.) planting, and subsequent corn yield. Ryelage compared to cover crop conserved more %ManureN‐R (2.6‐fold) and despite reduced corn yield, ryelage‐corn treatments with 3.6‐fold greater rye biomass produced 20% greater total harvested forage than cover crops. Compared to broadcasted manure (BM), injected manure (IM) reduced NH3 losses and increased ryelage biomass (42%) after September (EARLY) applications, %ManureN‐R (50%), %ManureN‐S at multiple depths, and total harvested forage (20%). Corn silage yield with IM compared to BM was also greater after all cover crop treatments (23%), all ryelage treatments in 2015 (35%), and ryelage with a November application (LATE) in 2014 (30%). Compared to EARLY, LATE applications increased %ManureN‐R in ryelage after BM (44%) and IM (50%), %ManureN‐S at multiple depths in both rye treatments, and corn silage yields with IM following cover crops (21%). Following ryelage, corn yields were not larger following greater %ManureN‐S in LATE IM versus BM, suggesting potential for more soil NO3 leaching loss with LATE IM. However, multiple management options reduced fall manure–N losses and conserved manure–N for crop utilization, allowing for farm management flexibility.

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.

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.

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 >10°C, and NO3− contents >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 >10 to 12°C, and soil NO3− contents >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.

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.

Ammonia Volatilization, Rice Yield, and Nitrogen Uptake Responses to Simulated Rainfall and Urease Inhibitor

Core Ideas Rainfall between preflood urea‐N application and flooding can be detrimental to rice grain yield. Use of the NBPT reduces yield loss from N transformations facilitated by rainfall between the urea application and flooding. Rainfall after urea application appears to reduce NH3 loss but enhance denitrification. The effect of rainfall between urea application and flood establishment on rice (Oryza sativa L.) grain yield has not been studied. We compared the effects of simulated rainfall amount and N‐(n‐butyl) thiophosphoric triamide (NBPT) urease inhibitor rate on NH3 volatilization and rice growth. Three field experiments were conducted and NH3 volatilization was measured in two trials for 11 d after urea application (DAA). Untreated urea (Urea) or NBPT‐treated urea (NBPT‐Urea) was subjected to six simulated rainfall amounts (0–25.4 mm) applied 5 to 15 h after fertilizer application and flooded 7 to 12 DAA. Cumulative NH3 loss from Urea accounted for 8.6% of the applied N (112–118 kg N ha−1) with no simulated rainfall and decreased quadratically to 0.6% with 25.4 mm of simulated rainfall. Cumulative NH3 loss from NBPT‐Urea decreased quadratically as simulated rainfall amount increased but loss was 0.2 to 2.0% of the applied N. Depending on the site, yields of rice fertilized with Urea decreased linearly or nonlinearly as simulated rainfall increased with the greatest yield produced by rice receiving no simulated rainfall. The yields of rice fertilized with NBPT‐Urea were not affected by simulated rainfall amount in two trials. In the third trial, the yields of rice receiving NBPT‐Urea decreased nonlinearly as simulated rainfall amount increased but were 8.9 to 18.1% (746–1376 kg ha−1) greater than the yields of Urea‐fertilized rice. Rainfall following urea application reduces NH3 loss but appears to increase N loss via denitrification. Based on yield results, total N loss was reduced when urea was treated with NBPT.

Urease Inhibitor NBPT on Ammonia Volatilization and Crop Productivity: A Meta‐Analysis

Core Ideas The volatilization losses averaged 31.0% of applied N for urea and 14.8% for NBPT‐treated urea. NBPT‐treated urea showed a potential yield increase of 5.3% for major crops. The effect of NBPT in reducing volatilization losses were reduced under high N rates. NBPT had a limited effect on increasing yield in coarse‐textured soils and for NBPT rates >1060 mg kg−1. The urease inhibitor N‐(n‐butyl) thiophosphoric triamide (NBPT) slows urea hydrolysis, reduces NH3 volatilization loss, and enhances N availability to plants. Even though most studies have proved the potential of NBPT‐treated urea to reduce NH3 loss, the benefits to increase crop yield have been less consistent, mainly because N is not always the limiting factor. A meta‐analysis was carried out to evaluate the effect of soil properties (e.g., soil pH, soil texture, soil organic C [SOC]), N rate, and NBPT concentration on NH3 volatilization loss and crop yield when comparing urea with NBPT‐treated urea. Regression analysis indicated cumulative NH3 loss of 31.0 and 14.8% of applied N for urea and NBPT‐treated urea, respectively, a 52% reduction in NH3 loss by using the urease inhibitor. The use of NBPT delayed NH3 loss. It took 4.8 and 8.3 d for 50% of the total NH3 loss to occur for urea and NBPT‐treated urea, respectively. The meta‐analyses indicated that when compared with urea, NBPT‐treated urea reduced NH3 volatilization loss across all soil pH classes, soil texture classes, SOC contents, N rates, and NBPT concentrations. The meta‐analysis indicated an average crop yield increase of 5.3% for NBPT‐treated urea compared with urea. This trend was observed for all classes of soil pH, SOC content, and N rate, but yield increases were limited in coarse‐textured soils and NBPT rates >1060 mg kg−1.

Ammonia loss from urea in grassland and its mitigation by the new urease inhibitor 2-NPT

SUMMARYFollowing the surface application of granulated urea to grassland, high ammonia (NH3) losses of up to 30% have been reported. The addition of a urease inhibitor (UI) to urea granules could be a way to abate these losses. Field experiments were conducted at two intensive grassland sites in 2007 and 2008 to evaluate the potential of the new UI N-(2-nitrophenyl) phosphoric triamide (2-NPT; concentrations of 0·75, 1·0 and 1·5 g N/kg) to reduce NH3 emissions resulting from the application of granulated urea. Ammonia losses were continuously measured on plots fertilized with urea, urea + 2-NPT, calcium ammonium nitrate and a control (0N). The measurements were made with a dynamic chamber system. All measurement periods were started after a period of precipitation with a following rainless period being forecasted. Results over measurement periods of 10 days following fertilization are presented. Ammonia losses following the application of granulated urea varied between 4·6 and 11·8 kg N/ha, corresponding to 4·2 up to 14·0% of the applied nitrogen. The addition of 2-NPT to urea granules at three concentrations significantly reduced NH3 losses by 69–100%. Comparable losses of NH3 were observed for urea containing the UI 2-NPT as well as calcium ammonium nitrate, and were not significantly different from the control treatment. No relationships between losses, meteorological factors and soil moisture were observed. The addition of the UI 2-NPT to urea granules applied on grassland effectively reduced NH3 losses.

Combined use of nitrification inhibitor and struvite crystallization to reduce the NH3 and N2O emissions during composting

Struvite crystallization (SCP) is combined with a nitrification inhibitor (dicyandiamide, DCD) to mitigate the NH3 and N2O emission during composting. The MgO and H3PO4 were added at a rate of 15% (mole/mole) of initial nitrogen, and the DCD was added at rates of 0%, 2.5%, 5.0%, 7.5% and 10% (w/w) of initial nitrogen respectively. Results showed that the combination use of SCP and DCD was phytotoxin free. The SCP could significantly reduce NH3 losses by 45–53%, but not the DCD. The DCD significantly inhibits nitrification when the content was higher than 50mgkg−1, and that could reduce the N2O emission by 76.1–77.6%. The DCD degraded fast during the thermophilic phase, as the nitrification will be inhibited by the high temperature and high free ammonia content in this stage, the DCD was suggested to be applied in the maturing periods by 2.5% of initial nitrogen.

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.

A new cost-effective method to mitigate ammonia loss from intensive cattle feedlots: application of lignite.

In open beef feedlot systems, more than 50% of dietary nitrogen (N) is lost as ammonia (NH3). Here we report an effective and economically-viable method to mitigate NH3 emissions by the application of lignite. We constructed two cattle pens (20 × 20 m) to determine the effectiveness of lignite in reducing NH3 emissions. Twenty-four steers were fed identical commercial rations in each pen. The treatment pen surface was dressed with 4.5 kg m−2 lignite dry mass while no lignite was applied in the control pen. We measured volatilised NH3 concentrations using Ecotech EC9842 NH3 analysers in conjunction with a mass balance method to calculate NH3 fluxes. Application of lignite decreased NH3 loss from the pen by approximately 66%. The cumulative NH3 losses were 6.26 and 2.13 kg N head−1 in the control and lignite treatment, respectively. In addition to the environmental benefits of reduced NH3 losses, the value of retained N nutrient in the lignite treated manure is more than $37 AUD head−1 yr−1, based on the current fertiliser cost and estimated cost of lignite application. We show that lignite application is a cost-effective method to reduce NH3 loss from cattle feedlots.

Minimizing ammonia volatilization from urea, improving lowland rice (cv. MR219) seed germination, plant growth variables, nutrient uptake, and nutrient recovery using clinoptilolite zeolite

The anionic nature and high cation exchange capacity (CEC) of clinoptilolite zeolite can be exploited to reduce ammonia (NH3) loss from urea and to improve soil chemical properties to increase nutrient utilization efficiency in lowland rice cultivation. A closed-dynamic airflow system was used to determine NH3 loss from treatments (20, 40, and 60 g clinoptilolite zeolite pot−1). Seed germination study was conducted to evaluate the effects of clinoptilolite zeolite on rice seed germination. A pot study was conducted to determine the effects of clinoptilolite zeolite on rice plant growth variables, nutrient uptake, nutrient recovery, and soil chemical properties. Standard procedures were used to determine NH3 loss, rice plant height, number of leaves, number of tillers, dry matter production, nutrient uptake, nutrient recovery, and soil chemical properties. Application of clinoptilolite zeolite (15%) increased shoot elongation of seedlings and significantly reduced NH3 loss (up to 26% with 60 g zeolite pot−1), and increased number of leaves, total dry matter, nutrient uptake, nutrient recovery, soil pH, CEC, and exchangeable Na+. Amending acid soils with clinoptilolite zeolite can significantly minimize NH3 loss and improve rice plant growth variables, nutrient uptake, nutrient recovery, and soil chemical properties. These findings are being validated in our ongoing field trials.

Controlled-release fertilizer, floating duckweed, and biochar affect ammonia volatilization and nitrous oxide emission from rice paddy fields irrigated with nitrogen-rich wastewater

It is of great concern that nitrogen-rich (N-rich) wastewater irrigation increases ammonia (NH3) volatilization from rice (Oryza sativa L.) paddy fields. A pilot-scale field trial was conducted to study the impact of different management practices on reducing NH3 volatilization and their subsequent impacts on nitrous oxide (N2O) emission from a paddy field irrigated with N-rich wastewater generated by livestock production and supplemented with urea N fertilizer. A total of 225 kg N ha−1 combined with urea and N-rich wastewater was split into basal, the first, and second supplementary applications for the following five treatments: urea N mixed with controlled-release N fertilizer (BBF), floating duckweed (FDW), biochar alone (BC), biochar mixed with calcium superphosphate (BCP), and control with no amendment (CK). Results showed that each treatment had similar pattern of NH3 volatilization and N2O emission after N application. Treatments of BBF, FDW, and BCP effectively reduced NH3 losses by 22.8, 55.2, and 39.2 %, respectively, compared with the CK. BBF treatment decreased NH3 volatilization after the first supplementary N fertilization; BCP treatment reduced NH3 volatilization after the basal fertilization; and FDW treatment reduced NH3 volatilization after both the basal and first supplementary fertilization. Besides controlling the NH3 volatilization, BCP treatment also reduced 19.5 % of N2O loss. However, BC alone suppressed N2O emission by 24.3 %, but did not reduce NH3 loss. The findings can practically guide farmers to choose the appropriate management practices in improving N use efficiency and minimizing the impact of fertilization on environmental quality.

Gaseous emissions from management of solid waste: a systematic review.

The establishment of sustainable soil waste management practices implies minimizing their environmental losses associated with climate change (greenhouse gases: GHGs) and ecosystems acidification (ammonia: NH3). Although a number of management strategies for solid waste management have been investigated to quantify nitrogen (N) and carbon (C) losses in relation to varied environmental and operational conditions, their overall effect is still uncertain. In this context, we have analyzed the current scientific information through a systematic review. We quantified the response of GHG emissions, NH3 emissions, and total N losses to different solid waste management strategies (conventional solid storage, turned composting, forced aerated composting, covering, compaction, addition/substitution of bulking agents and the use of additives). Our study is based on a meta-analysis of 50 research articles involving 304 observations. Our results indicated that improving the structure of the pile (waste or manure heap) via addition or substitution of certain bulking agents significantly reduced nitrous oxide (N2O) and methane (CH4) emissions by 53% and 71%, respectively. Turned composting systems, unlike forced aerated composted systems, showed potential for reducing GHGs (N2O: 50% and CH4: 71%). Bulking agents and both composting systems involved a certain degree of pollution swapping as they significantly promoted NH3 emissions by 35%, 54%, and 121% for bulking agents, turned and forced aerated composting, respectively. Strategies based on the restriction of O2 supply, such as covering or compaction, did not show significant effects on reducing GHGs but substantially decreased NH3 emissions by 61% and 54% for covering and compaction, respectively. The use of specific additives significantly reduced NH3 losses by 69%. Our meta-analysis suggested that there is enough evidence to refine future Intergovernmental Panel on Climate Change (IPCC) methodologies from solid waste, especially for solid waste composting practices. More holistic and integrated approaches are therefore required to develop more sustainable solid waste management systems.

Water Quality and Nitrogen Mass Loss from Anaerobic Lagoon Columns Receiving Pretreated Influent

Control methods are needed to abate NH losses from swine anaerobic lagoons to reduce the contribution of confined swine operations to air pollution. In a 15-mo meso-scale column study, we evaluated the effect of manure pretreatment on water quality, reduction of N losses, and sludge accumulation in swine lagoons using (i) enhanced solid-liquid separation with polymer (SS) and (ii) solid-liquid separation plus biological N treatment using nitrification-denitrification (SS + NDN). A conventional anaerobic lagoon was included as a control. Concentrations of total Kjeldahl N (TKN), total ammoniacal N (TAN), and NO-N were monitored during the course of the study, and the volumes of column liquid and sludge were used to estimate N mass flows. At the end of the study, TKN and TAN concentrations in the liquid of SS columns were 35 and 37% lower than the control, respectively, and TKN and TAN concentrations in SS + NDN were 97 and 99% lower than the control. The N mass flow analysis revealed that SS reduced total N inflow by 30% and SS + NDN by 82% compared with the control. The SS was ineffective at reducing NH losses compared with the control. Instead, SS + NDN effectively reduced total NH losses by 50%, most of which occurred during the first 6 mo of the study. Although both pretreatments can stop the mass accumulation of total N in sludge, SS + NDN had the advantage of improving water quality and abating NH emissions from treated lagoons. As an additional environmental benefit, SS + NDN effluents could be used for crop irrigation without the risk of NH losses during land application.

Effects of form of effluent, season and urease inhibitor on ammonia volatilization from dairy farm effluent applied to pasture

Purpose With land application of farm effluents from cows during housing or milking as an accepted practice, there are increasing concerns over its effect on nitrogen (N) loss through ammonia (NH3) volatilization. Understanding the relative extent and seasonal variation of NH3 volatilization from dairy effluent is important for the development of management practices for reducing NH3 losses. The objectives of this study were to determine potential NH3 losses from application of different types of dairy effluent (including both liquid farm dairy effluent (FDE) and semi-solid dairy farm manure) to a pasture soil during several contrasting seasons and to evaluate the potential of the urease inhibitor (UI)—N-(n-butyl) thiophosphoric triamide (NBTPT, commercially named Agrotain®) to reduce gaseous NH3 losses.

Potential of aeration flow rate and bio-char addition to reduce greenhouse gas and ammonia emissions during manure composting

Aeration is an important factor influencing CO2, CH4, N2O and NH3 emissions from the composting process. Both CH4 and N2O are potent greenhouse gases (GHG) of high importance. Here, we examined the effects of high and low aeration rates together with addition of barley straw with and without bio-char on GHG and NH3 emissions from composting cattle slurry and hen manure in small-scale laboratory composters. Depending on treatment, cumulative C losses via CO2 and CH4 emissions accounted for 11.4–22.5% and 0.004–0.2% of initial total carbon, while N losses as N2O and NH3 emissions comprised 0.05–0.1% and 0.8–26.5% of initial total nitrogen, respectively. Decreasing the flow rate reduced cumulative NH3 losses non-significantly (by 88%) but significantly increased CH4 losses (by 51%) from composting of cattle slurry with barley straw. Among the hen manure treatments evaluated, bio-char addition to composting hen manure and barley straw at low flow rates proved most effective in reducing cumulative NH3 and CH4 losses. Addition of bio-char in combination with barley straw to hen manure at both high and low flow rates reduced total GHG emissions (as CO2-equivalents) by 27–32% compared with barley straw addition alone. Comparisons of flow rates showed that low flow could be an alternative strategy for reducing NH3 losses without any significant change in N2O emissions, pointing to the need for well-controlled composting conditions if gaseous emissions are to be minimised.