Use of nitrogen process inhibitors for reducing gaseous nitrogen losses from land-applied farm effluents

Applications of dairy farm effluents to land may lead to ammonia (NH₃) volatilization and nitrous oxide (N₂O) emissions. Nitrogen (N) transformation process inhibitors, such as urease inhibitors (UIs) and nitrification inhibitors (NIs), have been used to reduce NH₃ and N₂O losses derived from agricultural N sources. The objective of this study was to examine the effects of amending dairy effluents with UI (N-(n-butyl) thiophosphoric triamide (NBTPT)) and NI (dicyandiamide (DCD)) on NH₃ and N₂O emissions. Treatments included either fresh or stored manure and either fresh or stored farm dairy effluent (FDE), with and without NBTPT (0.25 g kg^?1 N) or DCD (10 kg ha^?1), applied to a pasture on a free-draining volcanic parent material soil. The nutrient loading rate of FDE and manure, which had different dry matter contents (about 2 and 11 %, respectively) was 100 kg N ha^?1. Application of manure and FDE led to NH₃ volatilization (15, 1, 17 and 0.4 % of applied N in fresh manure, fresh FDE, stored manure and stored FDE, respectively). With UI (NBTPT), NH₃ volatilization from fresh manure was significantly (P?<?0.05) decreased to 8 % from 15 % of applied N, but the UI did not significantly reduce NH₃ volatilization from fresh FDE. The N₂O emission factors (amount of N₂O–N emitted as a percentage of applied N) for fresh manure, fresh FDE and stored FDE were 0.13?±?0.02, 0.14?±?0.03 and 0.03?±?0.01 %, respectively. The NI (DCD) was effective in decreasing N₂O emissions from stored FDE, fresh FDE and fresh manure by 90, 51 and 46 % (P?<?0.05), respectively. All types of effluent increased pasture production over the first 21 days after application (P?<?0.05). The addition of DCD resulted in an increase in pasture production at first harvest on day 21 (P?<?0.05). This study illustrates that UIs and NIs can be effective in mitigating NH₃ and N₂O emissions from land-applied dairy effluents.     

Nitrous oxide emissions from dairy farm effluent applied to a New Zealand pasture soil

A field experiment on permanent ryegrass–white clover pasture at AgResearch's Ruakura dairy farm near Hamilton, New Zealand quantified nitrous oxide (N₂O) emissions from different types of dairy effluent applied to soil at three seasons and evaluated the potential of dicyandiamide (DCD) (a nitrification inhibitor) to decrease gaseous N₂O emissions. Fresh or stored manure and farm dairy effluent (FDE; from dairy shed washings), with or without DCD (10 kg/ha), were applied at approximately 100 kg N/ha to plots on a well‐drained soil on volcanic parent material. A field chamber technique was used to measure N₂O emissions. Application of manure or FDE, both in fresh and stored forms, to pasture generally increased N₂O emissions. Overall N₂O emission factors (EF) varied between 0.01% and 1.87%, depending on application season and effluent type. EFs in spring and autumn were greater than those in summer (P < 0.05). Among the effluents, N₂O EFs were largest from fresh FDE (1.65%) during the spring measurement period, stored manure (1.87%) during the autumn and stored FDE (0.25%) during the summer. DCD was effective in decreasing N₂O EFs from fresh FDE, fresh manure, stored FDE and stored manure by 40–80%, 69–76%, 24–84% and 60–70%, respectively. DCD reduced N₂O emissions during the spring and autumn seasons more effectively than in the summer season.     

Treating farm dairy effluent with poly-ferric sulphate dramatically reduces phosphorus and E. coli leaching through subsurface drains—A physical drainage model study

Land application of farm dairy effluent (FDE) may lead to water contamination, by contaminants such as phosphorus (P) and E. coli. A new FDE treatment technology using poly-ferric sulphate (PFS) has been developed to recycle wastewater in FDE for washing the farmyard. A physical drainage model study was conducted to investigate the effect of treating FDE with PFS on phosphorus and E. coli leaching through model subsurface drains. Dissolved reactive phosphorus (DRP) and total phosphorus (TP) leaching losses from untreated effluent (FDE) averaged 3.48 kg P ha⁻¹ and 11.44 kg P ha⁻¹, respectively. The application of PFS-treated effluent (TE) resulted in significantly lower DRP and TP leaching losses at 0.24 kg P ha⁻¹ and 4.52 kg P ha⁻¹ for fresh TE and 0.27 kg P ha⁻¹ and 6.31 kg P ha⁻¹ for TE stored for 3 weeks before application (TE-S). Cumulative DRP lost to drainage water from the TE and TE-S treatments was 93.1% and 92.2% lower than that from the FDE treatments. Compared with the FDE treatment, there was a 98.27% and 99.99% reduction in E. coli in the drainage water from the TE and TE-S treatments. Plant biomass and P uptake were not affected by the effluent treatments. These results indicate that land application of PFS-treated effluent, fresh or stored, on drained pasture soils can produce significant environmental benefits by reducing the concentration and amount of P and E. coli in the drainage water, without adversely impacting plant growth.     

Ammonia volatilization from poultry manure-amended soil

Summary Poultry manure (PM) is commonly applied to cropland as a fertilizer, usually at rates determined by the nitrogen content of the manure. Limited information is available, however, on the volatilization of ammonia from poultry manure-amended soils, despite the effect these losses may have on the fertilizer value of the manure. This study was initiated to determine the influence of incorporation and residue cover on NH₃ losses from PM-amended soils. In the first experiment, a dynamic flow technique was used to measure NH₃ losses from 18 manures applied to a bare soil surface at a rate of 12 Mg ha^-1. In the second experiment, 3 of the 18 manures were incorporated either immediately, 24 h or 72 h after application. The third experiment compared the same three manures applied to a bare soil surface or to corn or soybean residues. Surface application of the manures resulted in the loss of from 4 to 31% of the total N applied in the manures. Incorporation of the PM with soil significantly reduced NH₃ loss with the greatest decrease following immediate incorporation. Crop residues either had no effect or slightly reduced NH₃ volatilization losses relative to PM application to a bare soil surface. Ammonia volatilization was not well correlated with individual manure properties, but a multiple regression approach using manure pH and total N content offered some promise as a means to segregate manures of the basis of volatilization potential.     

Effect of treated farm dairy effluent on E. coli,phosphorus and nitrogen leaching and greenhouse gas emissions: a field lysimeter study

Purpose

Land application of farm dairy effluent (FDE) to pasture soils is the preferred practice in New Zealand. Recently, a new FDE treatment technology has been developed to recycle the water for washing the yard Cameron and Di (J Soils Sediments 2018). Here we report a lysimeter study to compare the leaching losses of Escherichia coli, phosphorus (P), and nitrogen (N) and emissions of greenhouse gases from the treated FDE compared with the untreated original FDE.

Materials and methods

Lysimeters were collected from a Balmoral silt loam soil (Typic Dystrudept, USDA) and installed in a field trench facility. Treatments included (1) treated effluent (TE), (2) a mixture of TE and recycled water (M), (3) untreated original FDE (FDE), and (4) water as control. The effluents were applied at a surface application rate of 24 mm on each lysimeter in May and again in September 2017. Measurements included leaching losses of E. coli, total phosphorus (TP), dissolved reactive phosphorus (DRP), total mineral nitrogen (TN), ammonium-N (NH₄⁺-N), and nitrate-N (NO₃^?-N); emissions of nitrous oxide (N₂O), carbon dioxide (CO₂), and methane (CH₄); herbage yield; and N uptake.

Results and discussion

The results showed that E. coli, TP, and DRP leaching losses from the TE were 1.31?×?10¹⁰ cfu/ha, 0.26 kg P/ha, and 0.009 kg DRP/ha and from M treatments were 6.96?×?10⁸ cfu/ha, 0.18 kg P/ha, and 0.004 kg DRP/ha, respectively, which were significantly (P?<?0.05) lower than those from the FDE which were 4.21?×?10¹⁰ cfu/ha, 1.75 kg P/ha, and 0.034 kg DRP/ha, respectively. There were no significant differences in NO₃^?-N leaching losses amongst the different forms of effluents. There were no significant differences in total N₂O, CO₂ emissions, and CH₄ uptakes from the different effluents (P?<?0.05). Herbage dry matter yields and N uptakes were also similar in the different effluent-treated lysimeters.

Conclusions

Results from this research indicate that land application of the treated effluents (TE) or a mixture of TE plus clarified water (M) would result in significant environmental benefits by reducing E. coli and P leaching without increasing greenhouse gas emissions.

     

Use of CaCl2 to decrease ammonia volatilization after application of fresh and anaerobic chicken slurry to soil

Ammonia losses after surface application of fresh chicken slurry (15% solids) and anaer-obically stored chicken slurry (10% solids) to a silty clay soil (pH 6.9) at a rate equivalent to 34 m³ ha^?1 were studied in a laboratory incubation experiment. Total NH₃-N losses amounted to 29% of the initial uric acid-N+urea-N+NH⁺₄-N content of the fresh slurry and 28% of the initial NH⁺₄-N content of the anaerobic slurry. Peak rates of ammonia volatilization took place between 24 h and 48 h after application of the fresh slurry and within 5 h of application of the anaerobic slurry. The addition of CaCl₂ at a rate of 36 mg Ca g^?1 (dry wt) slurry decreased peak rates of ammonia volatilization from the fresh slurry by 73% and total losses by 37%. The decrease in total ammonia losses through CaCl₂ addition to the anaerobic slurry was only 8 %. The addition of CaCl₂ decreased CO₂ output from both slurries through precipitation of HCO₃^? as CaCO₃, thereby removing a source of alkalinity from the solution. The failure of the CaCl₂ addition to decrease significantly ammonia losses from the anaerobic slurry suggested that HCO₃^? was an important source of alkalinity driving ammonia volatilization in the fresh slurry, but not in the anaerobic slurry. CaCl₂, addition did not affect urea hydrolysis, nor net nitrogen mineralization. The decrease in ammonia loss achieved through CaCl₂ addition was however not associated with a parallel increase in ammonium concentrations in the soil. Further experiments showed that the ammonia retained by the CaCl₂, was probably fixed by the soil and rendered non-extractable by KCl.     

A new method to treat farm dairy effluent to produce clarified water for recycling and to reduce environmental risks from the land application of effluent

Purpose

There is increasing public concern about the amount of fresh water used on New Zealand dairy farms and the adverse impacts that farm dairy effluent (FDE) has on the environment. FDE mainly consists of fresh water (99%) with a small amount of solid material (1%). There is an opportunity to treat FDE to remove the colloidal solid material and recycle the water to wash the farm yard.

Materials and methods

A new method of treating FDE has been developed. The method uses a coagulant to flocculate and settle the colloidal particles in the FDE and thus produce the clarified water for recycling. The research and development programme involved three stages: (i) standard laboratory jar tests to establish the amount of coagulant required to treat the FDE, (ii) large tank tests to confirm the effectiveness of the coagulant at a larger scale and (iii) construction and testing of two pilot plants. A pasture field trial was conducted to test the effect of the clarified water and treated effluent on plant production.

Results and discussion

The new method of treating FDE was highly successful in removing the colloidal material and producing clarified water that can be recycled to wash the farm yard. The average turbidity of the clarified water from the first pilot plant was 52 nephelometric turbidity units (NTU) (a 97% reduction in NTU compared to the original FDE) and the average Escherichia coli concentration was 9 cfu per 100 mL (a 99.99% reduction compared to the original untreated FDE). The average total-phosphorus (P) concentration of the clarified water was 1.8 g m^?3 (94% reduction), dissolved reactive phosphorus (DRP) was <?0.1 g m^?3 (99% reduction) and total nitrogen (N) was reduced by >?70% (from 200 to 61 g m^?3). The average turbidity of the clarified water from the second pilot plant was <?20 NTU (a 99.5% reduction). There was no adverse impact from the land application of the clarified water or the treated FDE on plant growth.

Conclusions

A new method for treating farm dairy effluent was successfully developed that produced clarified water that could be recycled to wash the farm yard and had a lower potential risk of environmental impacts when applied to land than untreated FDE. Land application of the clarified water or the treated FDE had no adverse impact on plant growth.

     

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.     

Application of hydrochar and pyrochar to manure is not effective for mitigation of ammonia emissions from cattle slurry and poultry manure

Nitrogen (N) loss as ammonia (NH₃) from agricultural systems is one of the major sources of atmospheric pollutants and is responsible for more than 50% of global NH₃ emissions. Ammonia volatilization from animal manures may be altered by amendment with chars derived from pyrolysis (pyrochars) or hydrothermal carbonization (hydrochars) by providing exchange sites for ammonium (NH₄⁺) or changing the pH of manure. Pyrochar and hydrochar differ in chemical and structural composition, specific surface area, and pH and therefore may affect NH₃ volatilization differently. In a laboratory incubation experiment, we investigated the effect of pyrochar (pH 9.0) and hydrochar (pH 3.8) from Miscanthus on NH₃ emission after addition to poultry manure and cattle slurry. We analyzed manure treatments with and without char addition and acidification and determined the effect of char addition on immobilization of manure-derived NH₄⁺. Ammonia emission from pure poultry manure amounted 84% of the applied NH₄⁺-N, while 67% of the applied NH₄⁺-N was lost as NH₃ from cattle slurry. Addition of pyrochar or hydrochar had no or only marginal effects on NH₃ emissions except for a reduction in NH₃ emissions by 19% due to hydrochar application to CS (p?<?0.05), which seems to be primarily related to the char pH. Sorption of NH₄⁺ by admixture of chars to manure was generally small: between 0.1- and 0.5-mg NH₄⁺-N g^?1 chars were sorbed. This corresponds to between 0.1 and 3.5% of the NH₄⁺ applied, which obviously was not strong enough to reduce emissions of NH₃. Overall, our results do not provide evidence that addition of pyrochar or hydrochar to cattle slurry and poultry manure is an effective measure to reduce NH₃ volatilization.     

Presubmergence and green manure affect the transformations of nitrogen‐15‐labeled urea under lowland soil conditions

The effect of presubmergence and green manuring on various processes involved in [¹⁵N]‐urea transformations were studied in a growth chamber after [¹⁵N]‐urea application to floodwater. Presubmergence for 14 days increased urea hydrolysis rates and floodwater pH, resulting in higher NH₃ volatilization as compared to without presubmergence. Presubmergence also increased nitrification and subsequent denitrification but lower N assimilation by floodwater algae caused higher gaseous losses. Addition of green manure maintained higher NH₄⁺‐N concentration in floodwater mainly because of lower nitrification rates but resulted in highest NH₃ volatilization losses. Although green manure did not affect the KCl extractable NH₄⁺‐N from applied fertilizer, it maintained higher NH₄⁺‐N content due to its decomposition and increased mineralization of organic N. After 32 days about 36.9 % (T₁), 23.9 % (T₂), and 36.4 % (T₃) of the applied urea N was incorporated in the pool of soil organic N in treatments. It was evident that the presubmergence has effected the recovery of applied urea N.     

MSW Compost Reduces Nitrogen Volatilization During Dairy Manure Composting

Manures lose N through volatilization almost immediately after deposit. Attempts to control losses include the addition of a C source to stimulate nitrogen immobilization. Composting is a treatment process that recommends the addition of carbonaceous materials to achieve a C:N ratio of 30:1 to stimulate degradation and immobilize nitrogen. Dairies near cities may be able to reduce N loss from manures by composting with urban carbonaceous residues such as municipal solid waste (MSW) or MSW compost that, by themselves, have little agronomic value. Studies were conducted using a self-heating laboratory composter where dairy solids were mixed with MSW compost to determine the reduction of N loss during composting. One-to-one mixtures (v/v) of dairy manure solids and MSW compost were composted and NH₃ volatilization, CO₂ evolution and temperatures were compared to composting of manure alone. Addition of MSW compost resulted in increased CO₂ evolution and reduced N loss. Nitrogen loss from composting dairy manure alone was four to ten times greater than that from composting dairy manure mixed with MSW compost. Adjustment of the C:N ratio to 25 by adding MSW compost to manure appeared to be the major factor in reducing N losses.     

Effects of cotton (Gossypium hirsutum L.) straw and its biochar application on NH3 volatilization and N use efficiency in a drip-irrigated cotton field

Reducing ammonia (NH₃) volatilization is a practical way to increase nitrogen (N) fertilizer use efficiency (NUE). In this field study, soil was amended once with either cotton (Gossypium hirsutum L.) straw (6 t ha^?1) or its biochar (3.7 t ha^?1) unfertilized (0 kg N ha^?1) or fertilized (450 kg N ha^?1), and then soil inorganic N concentration and distribution, NH₃ volatilization, cotton yield and NUE were measured during the next two growing seasons. In unfertilized plots, NH₃ volatilization losses in the straw-amended and biochar-amended treatments were 38–40% and 42–46%, respectively, less than that in control (i.e., unamended soil) during the two growing seasons. In the fertilized plots, NH₃ volatilization losses in the straw-amended and biochar-amended treatments were 30–39% and 43–54%, respectively, less than that in the control. Straw amendment increased inorganic N concentrations, cotton yield, cotton N uptake and NUE during the first cropping season after application, but not during the second. In contrast, biochar increased cotton N uptake and NUE during both the first and the second cropping seasons after application. Furthermore, the effects of biochar on cotton N uptake and NUE were greater in the second year than in the first year. These results indicate that cotton straw and cotton straw biochar can both reduce NH₃ volatilization and also increase cotton yield, N uptake and NUE. In addition, the positive effects of one application of cotton straw biochar were more long-lasting than those of cotton straw.     

Estimation of Ammonia Volatilization from a Paddy Field after Application of Controlled-Release Urea Based on the Modified Jayaweera–Mikkelsen Model Combined with the Sherlock–Goh Model

The continuous airflow enclosures with an acid trap method was widely used to investigate ammonia (NH₃) volatilization in field; however, it could be time-consuming for the estimation of NH₃ volatilization in field with the application of controlled-release urea (CRU) because NH₃ volatilization with CRU application could occur during the entire crop growth period. An NH₃ volatilization estimation method based on the modified Jayaweera–Mikkelsen (J-M) model combined with the Sherlock–Goh model was used to simulate NH₃ volatilization in a paddy field after 255 kg N ha^?1 as CRU (polymer-coated urea with the concentration of 43% nitrogen, 100% for basal) and urea (70% for basal, 30% for topdressing) during the rice growth period including flooded and non-flooded periods in Wuxi, China. Results indicated that NH₃ volatilization can be modeled with the proposed measure because no significant difference (P< 0.001) was observed between the simulated values and the observed values; the correlation coefficient (r²) was 0.615 for CRU and 0.840 for urea during the flooded period, and 0.991 for CRU and 0.946 for urea during the non-flooded period. Compared with urea, NH₃ volatilization was minimized by 43.2% with the application of CRU based on simulated value within the rice growth period, which was 40.40 kg N ha^?1 for CRU and 78.62 kg N ha^?1 for urea during the flooded period, and 5.52 kg N ha^?1 for CRU and 2.33 kg N ha^?1 for urea during the non-flooded period. Therefore, CRU could be a promising nitrogen fertilizer to prevent NH₃ losses in the rice paddies at the investigated area.     

Ammonia volatilization following surface application of urea to tilled and no-till soils: A laboratory comparison

Broadcasting of urea to agricultural soils can result in considerable losses by NH₃ volatilization. However, it is unclear if the impact of this practice on NH₃ emissions is further enhanced when performed on no-till (NT) soils. The objective of this study was to compare NH₃ volatilization following broadcasting of urea to NT and moldboard plowed (MP) soils. Intact soil cores were taken shortly after harvest from NT and MP plots of three long-term tillage experiments in Québec (Canada) and stored for 4.5 months prior to incubation. Urea (14 g N m⁻²) was applied at the soil surface and NH₃ volatilization was measured for 30 d using an open incubation system. Mean cumulative NH₃ losses were greater (P < 0.001) in NT (3.00 g N m⁻²) than in MP (0.52 g N m⁻²). Several factors may have contributed to the higher emissions from the NT soils. Urease activity in the top 1 cm of soils was on average 4.2 times higher in NT than in MP soils. As a result, hydrolysis of urea occurred very rapidly in NT soils as indicated by enhanced NH₃ emissions 4 h after application of urea. The presence of crop residues at the surface of NT soils also decreased contact of the urea granules with the soil, possibly reducing adsorption of NH₄⁺ on soil particles. Lower volatilization on the MP soils may also have partly resulted from a fraction of urea granules falling into shallow cracks. Field trials are needed to confirm our finding that NT soils bear greater potential for NH₃ volatilization following surface application of urea than MP soils.     

Nitrification and acidification from urea application in red soil (Ferralic Cambisol) after different long-term fertilization treatments

Purpose

Long-term manure applications can prevent or reverse soil acidification by chemical nitrogen (N) fertilizer. However, the resistance to re-acidification from further chemical fertilization is unknown. The aim of this study was to examine the effect of urea application on nitrification and acidification processes in an acid red soil (Ferralic Cambisol) after long-term different field fertilization treatments.

Materials and methods

Soils were collected from six treatments of a 19-year field trial: (1) non-fertilization control, (2) chemical phosphorus and potassium (PK), (3) chemical N only (N), (4) chemical N, P, and K (NPK), (5) pig manure only (M), and (6) NPK plus M (NPKM; 70 % N from M). In a 35-day laboratory incubation experiment, the soils were incubated and examined for changes in pH, NH₄ ⁺, and NO₃ ^?, and their correlations from urea application at 80 mg N kg^?1(?80) compared to 0 rate (?0).

Results and discussion

From urea addition, manure-treated soils exhibited the highest acidification and nitrification rates due to high soil pH (5.75–6.38) and the lowest in the chemical N treated soils due to low soil pH (3.83–3.90) with no N-treated soils (pH 4.98–5.12) fell between. By day 35, soil pH decreased to 5.21 and 5.81 (0.54 and 0.57 unit decrease) in the NPKM-80 and M-80 treatments, respectively, and to 4.69 and 4.53 (0.43 and 0.45 unit decrease) in the control-80 and PK-80 treatments, respectively, with no changes in the N-80 and NPK-80 treatments. The soil pH decrease was highly correlated with nitrification potential, and the estimated net proton released. The maximum nitrification rates (K _max) of NPKM and M soils (14.7 and 21.6 mg N kg^?1 day^?1, respectively) were significantly higher than other treatments (2.86–3.48 mg N kg^?1 day^?1). The priming effect on mineralization of organic N was high in manure treated soils.

Conclusions

Field data have shown clearly that manure amendment can prevent or reverse the acidification of the red soil. When a chemical fertilizer such as urea is applied to the soil again, however, soil acidification will occur at possibly high rates. Thus, the strategy in soil N management is continuous incorporation of manure to prevent acidification to maintain soil productivity. Further studies under field conditions are needed to provide more accurate assessments on acidification rate from chemical N fertilizer applications.     

NH3 Volatilization,N2O Emission and Microbial Biomass Turnover from 15N-Labeled Manure Under Laboratory Conditions

On irrigated agricultural soils from semi-arid and arid regions, ammonia (NH₃) volatilization and nitrous oxide (N₂O) emission can be a considerable source of N losses. This study was designed to test the capture of ¹⁵N loss as NH₃ and N₂O from previous and recent manure application using a sandy, calcareous soil from Oman amended one or two times with ¹⁵N labeled manure to elucidate microbial turnover processes under laboratory conditions. The system allowed to detect ¹⁵N enrichments in evolved N₂O-N and NH₃-N of up to 17% and 9%, respectively, and total N, K₂SO₄ extractable N and microbial N pools from previous and recent ¹⁵N labeled manure applications of up to 7%, 8%, and 15%. One time manured soil had higher cumulative N₂O-N emissions (141 µg kg^?1) than repeatedly manured soil with 43 µg kg^?1 of which only 22% derived from recent manure application indicating a priming effect.     

Gaseous losses of fertilizer nitrogen from a citrus orchard in the red soil hilly region of Southeast China

The gaseous losses of fertilizer nitrogen (N) applied to agroecosystems are a major contributor to a host of environmental problems, inefficient production systems, and decreased N-use efficiency. These losses lead to the wastage of resources, increasing the greenhouse effect and harming human health. The red soil hilly region of Southeast China houses the biggest orchard area of the world, and nitrogen fertilizers are usually heavily applied to the orchard systems in China. Therefore, this study aimed to measure the gaseous losses of the fertilizer N by ammonia (NH₃) volatilization and denitrification losses using the venting method and acetylene inhibition method respectively, and to assess the potential environmental risk of NH₃ and nitrous oxide (N₂O) emission from this orchard system based on the recent orchard management practices. An experiment was conducted in an Ougan citrus (Citrus reticulata Blanco ‘Suavissima’) orchard in the red soil hilly region of Southeast China. Three fertilization treatments, including the control (no N fertilizer, CK), poultry manure (at a rate of 6.3 t/ha, OM), and conventional fertilization (OM 6.3 t/ha + chemical fertilizer 393 kg N/ha, CF), were used. In all treatments, the fertilizers were incorporated into the soil after application. The test results, which were continuously determined within one year, indicated that the NH₃ volatilization losses accounted for 4.5% of the OM nitrogen (OM-N) and 2.9% of the CF nitrogen (CF-N), whereas the denitrification N losses accounted for 2.1% of the OM-N and 2.9% of the CF-N. Overall, the total gaseous N losses (including NH₃ volatilization losses and denitrification N losses) were 5.8% in the CF treatment. A relatively higher N₂O flux, accounting for 1.8% of the CF-N, emitted from the CF treatment.     

Ammonia volatilization and carbon dioxide emission from poultry litter: Effects of fractionation and storage time

Abstract

In many poultry producing areas, the amounts of poultry litter generated exceeds the amounts needed for application to soil, as fertilizer, at environmentally safe rates. To reduce the amounts of litter produced, Ndegwa et al. (1991) proposed fractionating the litter to generate a fine fraction that could be used as fertilizer, and a coarser fraction that could be recycled into poultry houses as bedding material. Because the fine fraction may need to be stored for several months before land application, knowledge of the changes that occur during storage would be important from the point of view of litter utilization. The objective of this study was to monitor water and inorganic nitrogen (N) contents, as well as potential ammonia (NH₃) volatilization and carbon dioxide (CO₂) emission in samples of whole litter and fine fraction stored in an unheated building for 16 weeks. Potential NH₃ volatilization and CO₂ emission were measured at unamended water contents and at a water content of 0.5 kg kg^‐1. Water and inorganic N contents of the whole litter and fine fractions showed some fluctuations during the first 4 weeks, but remained relatively stable from weeks 4 to 16. At unamended water contents, potential NH₃ volatilization and CO₂ emission were relatively low and similar for the whole litter and the fine fraction. Also, potential NH₃ volatilization remained stable whereas CO₂ emission decreased with time. Increasing the water content to 0.5 kg kg^‐1significantly increased potential NH₃ volatilization and CO₂ emission in the whole litters and fine fractions, with larger increases usually observed in the fine fractions. At 0.5 kg kg^‐1, both potential NH₃ volatilization and CO₂emission decreased with time. These results suggest that the fine fraction and the whole litter should be stored at relatively low water contents to prevent N losses through NH₃ volatilization and possibly denitrification.     

Effects of rainfall and manure application on phosphorus leaching in field lysimeters during fallow season

Purpose

Transformation and transport of soil phosphorus (P) from chemical fertilizer or manure are affected by agronomic practices (i.e., fertilization, irrigation, and tillage) and numerous abiotic factors (i.e., temperature, drought, and rainfall). Previous studies on the effects of manure application on P loss were mostly conducted during cultivation and often using the laboratory column approach. Validated field observations by integrating P availability with the risk of P loss are few. This study aimed to evaluate the effects of rainfall and manure application on P leaching during fallow season.

Materials and methods

An in situ field lysimeter experiment was performed. Leachate was collected and analyzed for total P (TP) and dissolved reactive P (DRP). At the end of the lysimeter trial, soils were sampled incrementally to a depth of 40 cm with the following depth intervals: 0–4, 4–10, 10–20, 20–30, and 30–40 cm. Soil water extractable P (P_w) was analyzed and degree of P saturation (DPS) was calculated after oxalate and Mehlich-3 (M3) extractions.

Results and discussion

Phosphorus loading was found below 40 cm in all treatments and P was most concentrated in the 4–10 cm soil layer. High rainfall enhanced P leaching and consequently led to lower P_w and higher leachate DRP and TP than low rainfall. Furthermore, P leaching was observed regardless of manure application, with the highest leachate DRP (1.83 mg L^?1) and TP (7.46 mg L^?1) concentrations found at the end of experiment (day 53). Observed P leaching loads during fallow season (53 days) varied between 0.08 and 1.21 kg ha^?1. The thresholds of DPS indicating P leaching were identified at 18.9% DPS_M3(Ca) and 12.9% DPS_M3(Ca+Mg), respectively. In this study, the DPS_M3(Ca) and DPS_M3(Ca+Mg) values exceeded the corresponding thresholds in the upper 30-cm soil layer but did not reach the thresholds at 30–40 cm. Nevertheless, the leachate DRP and TP indicated soil P leaching.

Conclusions

The results showed that intensive rainfall could significantly increase P leaching from manure application. Moreover, P leaching could occur in fallow season even in the absence of manure input, which should be assessed by not only soil P sorption capacities, but also soil fertilization history and hydrologic conditions. Implementation of soil P level evaluation is critical before spreading manure on land to avoid P pollution. Cost-effective and applicable soil test methods are required to generate environmental indicators to classify agricultural lands for risk of P loss, providing basis to safe manure disposal.     

Nitrogen Fertilizers and NH3 Volatilization: Effect of Temperature and Soil Moisture

ABSTRACT

The volatilization of ammonia is the main reaction that decreases the efficiency of nitrogen fertilization and in order to reduce losses. new technologies such as addition of N-n-butyltriamide thiophosphate (NBPT) to the conventional urea granule (UNBPT) or the covering with polymer and sulfur (UPS) have been developed with the aim to optimize nitrogen fertilization. This work aimed to evaluate the volatilization of ammonia (NH₃) in conventional urea (CU) and fertilizers with associated technology under: (a) three temperature conditions (b) and three soil moisture management. The fertilizer CU presented the highest losses by volatilization of 25.93 mg dm^?3 while fertilizers with associated technology registered 23.93 mg dm^?3 and 8.26 mg dm^?3 for UNBPT and UPS. respectively. The highest volatilization of NH₃ was registered at 45°C for all fertilizers. Fertilizers with associated technology extended the N-release time. delaying the volatilization peak up to the 6^th day or even promoted the gradual release of fertilizer in the soil. such as UPS. The UNBPT showed the lowest volatilization values in the 1^st water application. while the CU had lower volatilization values at 25°C (14.48 mg dm^?3 NH₃) and 35°C (16.99 mg dm^?3 NH₃) when the matric potential was increased from ?100 to ?50 kPa in the 1^st application of water. The UPS did not differ from the volatilization values for the three times of water application.