Application technique and slurry co-fermentation effects on ammonia,nitrous oxide,and methane emissions after spreading: II. Greenhouse gas emissions

The aim of this study was to investigate the effect of different application techniques on greenhouse gas emission from co-fermented slurry. Ammonia (NH3), nitrous oxide (N2O), and methane (CH4) emissions were measured in two field experiments with four different application techniques on arable and grassland sites. To gather information about fermentation effects, unfermented slurry was also tested, but with trail hose application only. Co-fermented slurry was applied in April at a rate of 30 m3 ha(-1). Measurements were made every 4 h on the first day after application and were continued for 6 wk with gradually decreasing sampling frequency. Methane emissions were <150 g C ha(-1) from co-fermentation products and seemed to result from dissolved CH4. Only in the grassland experiment were emissions from unfermented slurry significantly higher, with wetter weather conditions probably promoting CH4 production. Nitrous oxide emission was significantly increased by injection on arable and grassland sites two- and threefold, respectively. Ammonia emissions were smallest after injection or trail shoe application and are discussed in the preceding paper. We evaluated the climatic relevance of the measured gas emissions from the different application techniques based on the comparison of CO2 equivalents. It was evident that NH3 emission reduction, which can be achieved by injection, is at least compensated by increased N2O emissions. Our results indicate that on arable land, trail hose application with immediate shallow incorporation, and on grassland, trail shoe application, bear the smallest risks of high greenhouse gas emissions when fertilizing with co-fermented slurry.     

Crusting of stored dairy slurry to abate ammonia emissions: pilot-scale studies

Storage of cattle slurry is a significant source of ammonia (NH3) emissions. Emissions can be reduced by covering slurry stores, but this can incur significant costs, as well as practical and technical difficulties. In this pilot-scale study, slurry was stored in small tanks (500 L) and the effectiveness of natural crust development for reducing NH3 emissions was assessed in a series of experiments. Also, factors important in crust development were investigated. Measurements were made of crust thickness and specially adapted tank lids were used to measure NH3 emissions. Slurry dry matter (DM) content was the most important factor influencing crust formation, with no crust formation on slurries with a DM content of <1%. Generally, crusts began to form within the first 10 to 20 d of storage, at which time NH3 emission rates would decrease. The formation of a natural crust reduced NH3 emissions by approximately 50%. The type of bedding used in the free stall barn did not influence crust formation, nor did ambient temperature or air-flow rate across the slurry surface. There was a large difference in crust formation between slurries from cattle fed a corn (Zea mays L.) silage-based diet and those fed a grass silage-based diet, although dietary differences were confounded with bedding differences. The inclusion of a corn starch and glucose additive promoted crust formation and reduced NH3 emission. The maintenance of a manageable crust on cattle slurry stores is recommended as a cost-effective means of abating NH3 emissions from this phase of slurry management.     

Effects of cattle slurry acidification on ammonia and methane evolution during storage

Slurry acidification before storage is known to reduce NH(3) emissions, but recent observations have indicated that CH(4) emissions are also reduced. We investigated the evolution of CH(4) from fresh and aged cattle slurry during 3 mo of storage as influenced by pH adjustment to 5.5 with sulfuric acid. In a third storage experiment, cattle slurry acidified with commercial equipment on two farms was incubated. In the manipulation experiments, effects of acid and sulfate were distinguished by adding hydrochloric acid and potassium sulfate separately or in combination, rather than sulfuric acid. In one experiment sulfur was also added to slurry as the amino acid methionine in separate treatments. In each treatment 20-kg portions of slurry (n = 4) were stored for 95 d. All samples were subsampled nine to 10 times for determination of NH(3) and CH(4) evolution rates using a 2-L flow-through system. In all experiments, the pH of acidified cattle slurry increased gradually to between 6.5 and 7. Acidification of slurry reduced the evolution of CH(4) by 67 to 87%. The greatest reduction was observed with aged cattle slurry, which had a much higher potential for CH(4) production than fresh slurry. Sulfate and methionine amendment to cattle slurry without pH adjustment also significantly inhibited methanogenesis, probably as a result of sulfide production. The study suggests that complex microbial interactions involving sulfur transformations and pH determine the potential for CH(4) emission during storage of cattle slurry, and that slurry acidification may be a cost-effective greenhouse gas mitigation option.     

Effect of cattle slurry separation on greenhouse gas and ammonia emissions during storage

Storage of cattle slurry leads to emissions of methane (CH(4)), nitrous oxide (N(2)O), ammonia (NH(3)), and carbon dioxide (CO(2)). On dairy farms, winter is the most critical period in terms of slurry storage due to cattle housing and slurry field application prohibition. Slurry treatment by separation results in reduced slurry dry matter content and has considerable potential to reduce gaseous emissions. Therefore, the efficiency of slurry separation in reducing gaseous emissions during winter storage was investigated in a laboratory study. Four slurry fractions were obtained: a solid and a liquid fraction by screw press separation (SPS) and a supernatant and a sediment fraction by chemically enhanced settling of the liquid fraction. Untreated slurry and the separated fractions were stored in plastic barrels for 48 d under winter conditions, and gaseous emissions were measured. Screw press separation resulted in an increase of CO(2) (650%) and N(2)O (1240%) emissions due to high releases observed from the solid fraction, but this increase was tempered by using the combined separation process (CSP). The CSP resulted in a reduction of CH(4) emissions ( approximately 50%), even though high emissions of CH(4) (46% of soluble C) were observed from the solid fraction during the first 6 d of storage. Screw press separation increased NH(3) emissions by 35%, but this was reduced to 15% using the CSP. During winter storage greenhouse gas emissions from all treatments were mainly in the form of CH(4) and were reduced by 30 and 40% using SPS and CSP, respectively.     

Nitrogen fertilizer replacement value of cattle slurry in grassland as affected by method and timing of application

Slurry application with methods such as trailing shoe (TS) results in reduced emissions of ammonia (NH3) compared with broadcast application using splashplate (SP). Timing the application during cool and wet weather conditions also contributes to low NH3 emissions. From this perspective, we investigated whether reduced NH3 emissions due to improved slurry application method and timing results in an increase in the nitrogen (N) fertilizer replacement value (NFRV). The effects of application timing (June vs. April) and application method (TS vs. SP) on the apparent N recovery (ANR) and NFRV from cattle slurry applied to grassland were examined on three sites over 3 yr in randomized block experiments. The NFRV was calculated using two methods: (i) NFRV(N) based on the ANR of slurry N relative to mineral N fertilizer; and (ii) NFRV(DM) based on DM yield. The TS method increased the ANR, NFRV(N), and NFRV(DM) compared with SP in the 40- to 50-d period following slurry application by 0.09, 0.10, and 0.10 kg kg(-1), respectively. These values were reduced to 0.07, 0.06, and 0.05 kg kg(-1), respectively, when residual harvests during the rest of the year were included. The highest NFRV(DM) for the first harvest period was with application in April using STS (0.30 kg kg(-1)), while application in June with SP had the Slowest (0.12 kg kg(-1)). The highest NFRV(DM) for the cumulative harvest period was with application in April using TS (0.38 kg kg(-1)), while application in June with SP had the lowest (0.17 kg kg(-1)). Improved management of application method, by using TS instead of SP, and timing, by applying slurry in April rather than June, offer potential to increase the NFRV(DM) of cattle slurry applied to grassland.     

Dairy slurry application method impacts ammonia emission and nitrate in no-till corn silage

Reducing ammonia (NH3) emissions through slurry incorporation or other soil management techniques may increase nitrate (NO3) leaching, so quantifying potential losses from these alternative pathways is essential to improving slurry N management. Slurry N losses, as NH3 or NO3 were evaluated over 4 yr in south-central Wisconsin. Slurry (i.e., dairy cow [Bos taurus] manure from a storage pit) was applied each spring at a single rate (-75 m3 ha(-1)) in one of three ways: surface broadcast (SURF), surface broadcast followed by partial incorporation using an aerator implement (AER-INC), and injection (INJ). Ammonia emissions were measured during the 120 h following slurry application using chambers, and NO3 leaching was monitored in drainage lysimeters. Yield and N3 uptake of oat (Avena sativa L.), corn (Zea mays L.), and winter rye (Secale cereale L.) were measured each year, and at trial's end soils were sampled in 15- to 30-cm increments to 90-cm depth. There were significant tradeoffs in slurry N loss among pathways: annual mean NH3-N emission across all treatments was 5.3, 38.3, 12.4, and 21.8 kg ha(-1) and annual mean NO3-N leaching across all treatments was 24.1, 0.9, 16.9, and 7.3 kg ha' during Years 1, 2, 3, and 4, respectively. Slurry N loss amounted to 27.1% of applied N from the SURF treatment (20.5% as NH3-N and 6.6% as NO,-N), 23.3% from AER-INC (12.0% as NH3-N and 11.3% as NO3-N), and 9.19% from INJ (4.4% as NH3-N and 4.7% as NO3-N). Although slurry incorporation decreased slurry N loss, the conserved slurry N did not significantly impact crop yield, crop N uptake or soil properties at trial's end.     

The effect of cattle slurry electroflotation products as fertilizers on gaseous emissions and grassland yield

The climatic conditions of the Basque Country (northern Spain) provide the favorable conditions for the growth of grasslands and the development of livestock enterprises. The intensification of the farms is leading to serious environmental risks due to the great generation of manures and slurries and their subsequent inefficient management. Their application involves N losses that can be pollutant. The environmental company ADE BIOTEC S.L. is developing the process called "electroflotation" with the aim of reducing the volume of slurries from intensive livestock farms. The process consists basically of an electrolysis of the slurry catalyzed by iron which leads to the flocculation of the solid particles, giving as a final result a solid and a liquid fraction. The objective of this work was to assess the usefulness of these two fractions as fertilizers. With this aim, the environmental risk of their application was determined regarding gaseous emissions to the atmosphere (i.e., of NO, NH(3), N(2)O, and CO(2)) and their fertilizer capacity was investigated by determining their effects on grassland yield and N uptake in comparison to the untreated slurry. The untreated slurry and the solid and the liquid fractions were all applied at a rate of 70 kg NH(4)(+)-N ha(-1). The application of the products of electroflotation did not affect N(2)O and CO(2) losses, being of the same magnitude as those caused by the application of the original slurry. However, after their application, a reduction in NH(3) volatilization losses was induced in the short term and a reduction in NO losses was caused in the long term. The solid and liquid fractions both increased biomass yield with respect to the untreated slurry. The solid fraction even induced a higher N uptake than the liquid fraction and the untreated slurry.     

3,4-Dimethylpyrazol phosphate effect on nitrous oxide, nitric oxide, ammonia, and carbon dioxide emissions from grasslands

Intensively managed grasslands are potentially a large source of NH3, N2O, and NO emissions because of the large input of nitrogen (N) in fertilizers. Addition of nitrification inhibitors (NI) to fertilizers maintains soil N in ammonium form. Consequently, N2O and NO losses are less likely to occur and the potential for N utilization is increased, and NH3 volatilization may be increased. In the present study, we evaluated the effectiveness of the nitrification inhibitor 3,4-dimethylpyrazol phosphate (DMPP) on NH3, N2O, NO, and CO2 emissions following the application of 97 kg N ha(-1) as ammonium sulfate nitrate (ASN) and 97 kg NH4+ -N ha(-1) as cattle slurry to a mixed clover-ryegrass sward in the Basque Country (northern Spain). After slurry application, 16.0 and 0.7% of the NH4+ -N applied was lost in the form of N2O and NO, respectively. The application of DMPP induced a decrease of 29 and 25% in N2O and NO emissions, respectively. After ASN application 4.6 and 2.8% of the N applied was lost as N2O and NO, respectively. The application of DMPP with ASN (as ENTEC 26; COMPO, Münster, Germany) unexpectedly did not significantly reduce N2O emissions, but induced a decrease of 44% in NO emissions. The amount of NH4+ -N lost in the form of NH3 following slurry and slurry + DMPP applications was 7.8 and 11.0%, respectively, the increase induced by DMPP not being statistically significant. Levels of CO2 emissions were unaffected in all cases by the use of DMPP. We conclude that DMPP is an efficient nitrification inhibitor to be used to reduce N2O and NO emissions from grasslands.     

Application technique and slurry co-fermentation effects on ammonia,nitrous oxide,and methane emissions after spreading: I. Ammonia volatilization

Ammonia emissions after spreading animal manure contribute a major share to N losses from agriculture. There is an increasing interest in anaerobic co-digestion of liquid manure with organic additives. This fermentation results in a change of physical and chemical parameters of the slurry. Among these are an increased pH and ammonium content, implying a higher risk of NH3 losses from fermentation products. To compare different application techniques and the effect of fermentation on NH3 volatilization, we used the standard comparison method and tested it for reliability. This method seems to be perfectly suited for experiments with a large number of treatments and replicates if prerequisites concerning the experimental layout are considered. We tested four different application techniques on arable and grassland sites. The more the substrate was incorporated into the soil or applied near the soil surface on the grassland site, the less NH3 was lost. Injection of the substrate reduced losses to less than 10% of applied NH4+ on both sites, whereas losses after splash plate application amounted to more than 30%. Trail shoe application on grassland performed as well as injection. Harrowing on arable land also reduced emissions efficiently, if harrowing occurred within the first 2 h after application. Emissions from trail hose-applied co-fermentation product were not greater than from unfermented slurry. Better infiltration of the less viscous substrate seemed to have compensated for the increased loss potential.     

Low-disturbance manure incorporation effects on ammonia and nitrate loss

Low-disturbance manure application methods can provide the benefits of manure incorporation, including reducing ammonia (NH3) emissions, in production systems where tillage is not possible. However, incorporation can exacerbate nitrate (NO3?) leaching. We sought to assess the trade-offs in NH3 and NO3? losses caused by alternative manure application methods. Dairy slurry (2006-2007) and liquid swine manure (2008-2009) were applied to no-till corn by (i) shallow (<10 cm) disk injection, (ii) surface banding with soil aeration, (iii) broadcasting, and (iv) broadcasting with tillage incorporation. Ammonia emissions were monitored for 72 h after application using ventilated chambers and passive diffusion samplers, and NO3? leaching to 80 cm was monitored with buried column lysimeters. The greatest NH3 emissions occurred with broadcasting (35-63 kg NH3-N ha?), and the lowest emissions were from unamended soil (<1 kg NH-N ha?1). Injection decreased NH-N emissions by 91 to 99% compared with broadcasting and resulted in lower emissions than tillage incorporation 1 h after broadcasting. Ammonia-nitrogen emissions from banding manure with aeration were inconsistent between years, averaging 0 to 71% that of broadcasting. Annual NO3? leaching losses were small (<25 kg NO3-N ha?1) and similar between treatments, except for the first winter when NO3? leaching was fivefold greater with injection. Because NO3? leaching with injection was substantially lower over subsequent seasons, we hypothesize that the elevated losses during the first winter were through preferential flow paths inadvertently created during lysimeter installation. Overall, shallow disk injection yielded the lowest NH3 emissions without consistently increasing NO3? leaching, whereas manure banding with soil aeration conserved inconsistent amounts of N.     

Evaluating slurry broadcasting and injection to ley for phosphorus losses and fecal microorganisms in surface runoff

The recent growth in the size of dairy cattle farms and the concentration of farms into smaller areas in Finland may increase local water pollution due to increased manure production and slurry application to grass. Therefore, a field study was conducted to monitor losses of total phosphorus (TP), dissolved reactive phosphorus (DRP), and fecal microorganisms in surface runoff from a perennial ley. Cattle slurry was added once a year in June 1996-1997 (Study I) and biannually in June and October 1998-2000 (Study II). The slurry was surface broadcast or injected into the clay soil. The field had a slope of 0.9 to 1.7%. Mineral fertilizer was applied on control plots. Biannual slurry broadcasting increased DRP (p < 0.001) and TP losses (p < 0.001) and numbers of fecal microorganisms in surface runoff waters. The highest losses of TP (2.7 kg ha(-1) yr(-1)) and DRP (2.2 kg ha(-1) yr(-1)) and the highest numbers of fecal coliforms (880 colony-forming units [CFU] per 100 mL) and somatic coliphages (2700 plaque-forming units [PFU] per 100 mL) were measured after broadcasting slurry to wet soil followed by rainfall in fall 1998. Injection reduced the TP and DRP losses in surface runoff by 79 and 86%, respectively, compared with broadcasting (17 Oct. 1998-27 Oct. 1999). Corresponding numbers for fecal coliforms were 350 CFU (100 mL)(-1) and for somatic coliphages were 110 PFU (100 mL)(-1) in surface runoff after injection in October 1998. Slurry injection should be favored when spreading slurry amendments to grassland to avoid losses of P and fecal microorganisms in runoff to surface waters.     

Dependence of ammonia emissions from housing on the time cattle spent inside

Buildings housing cattle contribute 19% (42 kt NH3-N yr(-1)) of total UK ammonia (NH3) emissions. In the UK there is not usually an abrupt switch from cattle being kept inside to when they are turned out to graze 24 h a day. Moreover, during the summer dairy cows return to the farm twice a day to be milked and may spend some time inside buildings. Hence, there is uncertainty over the treatment of the transitional and summer periods when inventorying NH3 emissions. The aim of this study was to measure, under controlled and replicated conditions, the relationship between the number of hours cattle spend in buildings and the NH3 emissions from those buildings. Our results indicate that NH3 emissions decrease as the proportion of the day cattle spend in the buildings decreases, although the trend is not linear. Daily emission rates from cattle housed for 2 h ranged from 1.6 to 6.2 g NH3-N lu(-1) whereas emissions from cattle housed for 24 h ranged from 8.1 to 24.1 g NH3-N lu(-1). To significantly reduce NH3 emissions in comparison to those from buildings where cattle are housed for 24 h, the occupancy would have to be reduced to no more than 6 h each day. Thus, the strategy of extending the grazing season by allowing cattle to graze for c. 4 to 12 h during the winter is unlikely to reduce NH3 emissions from buildings or overall.     

Redistribution of slurry components as influenced by injection method, soil, and slurry properties

The distribution of moisture, degradable C, and N after direct injection of slurry can affect the turnover and plant availability of slurry N. This study examined effects of injection method, soil conditions, and slurry properties on the infiltration of several slurry components under practical conditions. The water retention capacity of 22 pig and cattle slurries was quantified by dialysis at -0.016, -0.047, and -0.100 MPa. All slurries followed the relationship: relative water loss = 1/(1 + aVS[volatile solids]), indicating that retention of liquids in the slurry injection zone can be predicted from slurry VS and soil water potential. Two-disc injection and harrow tine injection were simulated (no slurry applied) in five trials. Two trials indicated that disc injection resulted in higher permeability compared with harrow tine injection. In a separate experiment, soil moisture and dissolved ions were monitored in and around injection slits amended with pig or cattle slurry. Moisture gradients, which were recorded with small printed-circuit-board (PCB) time-domain-reflectometry (TDR) probes, were temporally stable and reestablished following rainfall. Slit sections with pig and cattle slurry containing 13C-acetate and 15N-ammonium showed a shift in the 13C to 15N ratio of the injection zone within 24 h, which was explained by removal of dissolved C and/or retention of NH4+. Cattle slurry was more concentrated around the injection slit than pig slurry, and greater contact between slurry and soil was obtained with harrow tine injection. The heterogeneity of slurry C and N distribution after direct injection should be accounted for in models describing slurry N turnover.     

Nitrous oxide and ammonia fluxes in a soybean field irrigated with swine effluent

In the United States, swine (Sus scrofa) operations produce more than 14 Tg of manure each year. About 30% of this manure is stored in anaerobic lagoons before application to land. While land application of manure supplies nutrients for crop production, it may lead to gaseous emissions of ammonia (NH3) and nitrous oxide (N2O). Our objectives were to quantify gaseous fluxes of NH3 and N2O from effluent applications under field conditions. Three applications of swine effluent were applied to soybean [Glycine max (L.) Merr. 'Brim'] and gaseous fluxes were determined from gas concentration profiles and the flux-gradient gas transport technique. About 12% of ammonium (NH4-N) in the effluent was lost through drift or secondary volatilization of NH3 during irrigation. An additional 23% was volatilized within 48 h of application. Under conditions of low windspeed and with the wind blowing from the lagoon to the field, atmospheric concentrations of NH3 increased and the crop absorbed NH3 at the rate of 1.2 kg NH3 ha(-1) d(-1), which was 22 to 33% of the NH3 emitted from the lagoon during these periods. Nitrous oxide emissions were low before effluent applications (0.016 g N2O-N ha(-1) d(-1)) and increased to 25 to 38 g N2O-N ha(-1) d(-1) after irrigation. Total N2O emissions during the measurement period were 4.1 kg N2O-N ha(-1), which was about 1.5% of total N applied. The large losses of NH3 and N2O illustrate the difficulty of basing effluent irrigation schedules on N concentrations and that NH3 emissions can significantly contribute to N enrichment of the environment.     

Daily, monthly, seasonal, and annual ammonia emissions from Southern High Plains cattle feedyards

Ammonia emitted from beef cattle feedyards adds excess reactive N to the environment, contributes to degraded air quality as a precursor to secondary particulate matter, and represents a significant loss of N from beef cattle feedyards. We used open path laser spectroscopy and an inverse dispersion model to quantify daily, monthly, seasonal, and annual NH emissions during 2 yr from two commercial cattle feedyards in the Panhandle High Plains of Texas. Annual patterns of NH fluxes correlated with air temperature, with the greatest fluxes (>100 kg ha d) during the summer and the lowest fluxes (<15 kg ha d) during the winter. Mean monthly per capita emission rate (PCER) of NH-N at one feedyard ranged from 31 g NH-N head d (January) to 207 g NH-N head d (October), when increased dietary crude protein from wet distillers grains elevated emissions. Ammonia N emissions at the other feedyard ranged from 36 g NH-N head d (January) to 121 g NH-N head d (September). Monthly fractional NH-N loss ranged from a low of 19 to 24% to a high of 80 to 85% of fed N at the two feedyards. Seasonal PCER at the two feedyards averaged 60 to 71 g NH-N head d during winter and 103 to 158 g NH-N head d during summer. Annually, PCER was 115 and 80 g NH-N head d at the two feedyards, which represented 59 and 52% of N fed to the cattle. Detailed studies are needed to determine the effect of management and environmental variables such as diet, temperature, precipitation, and manure water content on NH emissions.     

Quantifying ammonia emissions from a cattle feedlot using a dispersion model

Livestock manure is a significant source of ammonia (NH3) emissions. In the atmosphere, NH3 is a precursor to the formation of fine aerosols that contribute to poor air quality associated with human health. Other environmental issues result when NH3 is deposited to land and water. Our study documented the quantity of NH3 emitted from a feedlot housing growing beef cattle. The study was conducted between June and October 2006 at a feedlot with a one-time capacity of 22,500 cattle located in southern Alberta, Canada. A backward Lagrangian stochastic (bLS) inverse-dispersion technique was used to calculate NH3 emissions, based on measurements of NH3 concentration (open-path laser) and wind (sonic anemometer) taken above the interior of the feedlot. There was an average of 3146 kg NH3 d(-1) lost from the entire feedlot, equivalent to 84 microg NH3 m(-2) s(-1) or 140 g NH3 head(-1) d(-1). The NH3 emissions correlated with sensible heat flux (r2 = 0.84) and to a lesser extent the wind speed (r2 = 0.56). There was also evidence that rain suppressed the NH3 emission. Quantifying NH3 emission and dispersion from farms is essential to show the impact of farm management on reducing NH3-related environmental issues.     

Co-digestion of animal slurry can increase short-term nitrogen recovery by crops

Co-digestion changes slurry characteristics and is supposed to increase short-term nitrogen (N) uptake by crops after application. A higher N uptake from slurry reduces the need for additional mineral N fertilizer. If farmers apply co-digested slurry (CS), a higher N recovery has to be taken into account to prevent losses to the environment. Since data on the effects of co-digestion on N recovery by crops are scarce, a pot experiment was performed. The apparent N recovery (ANR) of five different co-digested pig slurries was compared with their raw source slurries (RS) during 105 d after a single fertilization of ryegrass (Lolium perenne L.), grown under controlled conditions. Slurry was mixed with sandy soil and grass was cut every 35 d. The results show that co-digestion increased (p < 0.05) the ANR at first cut on average from 39 to 50%, at second cut from 7 to 9% (p < 0.05), and had no effect on ANR at third cut (3%). The ANR increase at first cut was likely due to an increase of the NH(4)-N/total N ratio along with a decrease of the organic C/total N ratio of slurry during co-digestion. Field application may under certain circumstances decrease N fertilizer value of CS, due to a higher NH(3) emission compared to RS. A potential ANR increase may then be reduced, absent, or even become a decrease. Under comparable NH(3) emissions, however, CS can in the short term be more valuable as an N fertilizer than RS, and fertilizer savings can likely be realized.     

Comparisons of soil surface sealing methods to reduce fumigant emission loss

State and federal regulatory agencies depend on quality field data for determining the effects of agricultural management practices on fumigant emissions to develop sound, science-based policies and regulations on preplant soil fumigants. Field plot tests, using growers' standard field operation procedures, were used to simultaneously determine the effectiveness of several commonly proposed emission reduction methods, in a trial involving shank injection of Telone II [a.i. 1,3-dichloropropnene (1,3-D)] to a sandy loam soil to a target rate of 372 kg ha(-1). The experiment was conducted in late September 2008 in the San Joaquin Valley of California. Fumigant emissions were captured using dynamic flux chambers. The results showed that virtually impermeable film (VIF) reduced emissions >95% when compared to bare soil, and the glue joints in the film did not significantly affect the tarp performance. The VIF also created a more uniform distribution of gaseous fumigant in the soil profile, which would likely benefit pest control efficacy. Standard high-density polyethylene (HDPE) tarp reduced total 1,3-D emissions about 50% (higher than most reported values) in this trial, whereas postfumigation intermittent water treatments (seals) reduced cumulative emission losses by approximately 20%. Adding 49.4 Mg ha (equivalent to 20 tons per acre) of composted dairy manure to surface soils did not reduce 1,3-D emissions during this experiment. Use of VIF was the most promising technique in reducing emissions and has the potential to allow lower application rates while providing satisfactory pest control.     

Ammonia volatilization from surface-banded and broadcast application of liquid dairy manure on grass forage

Manure can provide valuable nutrients, especially N, for grass forage, but high NH, volatilization losses from standard surface-broadcast application limits N availability and raises environmental concerns. Eight field trials were conducted to evaluate the emission of NH, from liquid dairy manure, either surface broadcast or applied in narrow surface bands with a trailing-foot implement. Manure was applied using both techniques at rates of approximately 25 and 50 m3 ha(-1) on either orchardgrass (Dactylis glomerata L.) on a well-drained silt loam or reed canarygrass (Phalaris arundinacea L.) on a somewhat poorly drained clay soil. Ammonia emission was measured with a dynamic chamber/equilibrium concentration technique. High NH3 emission rates in broadcast treatments, especially at the high rate (2 to 13 kg ha(-1) h(-1)), occurred during the first few hours after spreading, followed by a rapid reduction to low levels (<0.5 kg ha(-1) h(-1) in most cases) by 24 h after spreading and in subsequent days. Band treatments often followed the same pattern but with initial rates substantially lower and with a less dramatic decrease over time. Total estimated NH3 losses from broadcast application, as a percent of total ammoniacal N (TAN) applied, averaged 39% (range of 20 to 59%) from the high manure rate and 25% (range of 9 to 52%) from the low rate. Band spreading reduced total NH3 losses by an average of 52 and 29% for the high and low manure rates, respectively. Results show that the trailing-foot band application method can reduce NH3 losses and conserve N for perennial forage production.     

Subsurface application of manures slurries for conservation tillage and pasture soils and their impact on the nitrogen balance

Injection of cattle and swine slurries can provide soil incorporation in no-till and perennial forage production. Injection is expected to substantially reduce N loss due to ammonia (NH3) volatilization, but a portion of that N conservation may be offset by greater denitrification and leaching losses. This paper reviews our current knowledge of the impacts of subsurface application of cattle and swine slurries on the N balance and outlines areas where a greater understanding is needed. Several publications have shown that liquid manure injection using disk openers, chisels, or tines can be expected to Sreduce NH, emissions by at least 40%, and often by 90% or more, relative to broadcast application. However, the limited number of studies that have also measured denitrification losses have shown that increased denitrification with subsurface application can offset as much as half of the N conserved by reducing NH3 emissions. Because the greenhouse gas nitrous oxide (N2O) is one product of denitrification, the possible increases in N2O emission with injection require further consideration. Subsurface manure application generally does not appear to increase leaching potential when manure is applied at recommended rates. Plant utilization of conserved N was shown in only a portion of the published studies, indicating that further work is needed to better synchronize manure N availability and crop uptake. At this time in the United States, the economic and environmental benefits from reducing losses of N as NH3 are expected to outweigh potential liability from increases in denitrification with subsurface manure application. To fully evaluate the trade-offs among manure application methods, a detailed environmental and agricultural economic assessment is needed to estimate the true costs of potential increases in NO2O emissions with manure injection.