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.     

Atmospheric ammonia,volatile fatty acids,and other odorants near beef feedlots

Intensive livestock operations can release odorous gases from stored or land-applied manure. We measured concentrations of dust and 14 odor-causing gases at increasing distances from four feedlots near Lethbridge, southern Alberta, Canada. Concentration was determined from the amount of total dust or gas accumulated in the sampIers, and the volume of air sampled. Adjacent the feedlots, the maximum concentration of many volatile fatty acids exceeded reported odor detection thresholds; the maximum ammonia concentration was close to the threshold. Ammonia and butyric acid approached or exceeded their individual odor thresholds as far as 200 m downwind of the feedlots. Highest concentrations were measured adjacent to land where manure was being applied. None of the odorant concentrations exceeded their irritation threshold. There was a positive relationship between ammonia concentration and odor intensity as well as dry deposition. Much of the emitted ammonia was deposited to soil immediately downwind, enough to supply all the nitrogen needed for crop growth. Odorant concentrations declined sharply with distance, though measurable odor occasionally persisted to 1 km from the feedlot, beyond the minimum separation guidelines (Alberta) for a single residential dwelling. The weekly averaged total suspended particulates (> 5 microm) were below the Alberta guideline criterion except for one period. Differences among feedlots in odorant plume concentrations were partly related to the stocking density of feedlots, which presumably affects manure moisture and amount of volatiles within the pens.     

Tillage, cropping systems, and nitrogen fertilizer source effects on soil carbon sequestration and fractions

Quantification of soil carbon (C) cycling as influenced by management practices is needed for C sequestration and soil quality improvement. We evaluated the 10-yr effects of tillage, cropping system, and N source on crop residue and soil C fractions at 0- to 20-cm depth in Decatur silt loam (clayey, kaolinitic, thermic, Typic Paleudults) in northern Alabama, USA. Treatments were incomplete factorial combinations of three tillage practices (no-till [NT], mulch till [MT], and conventional till [CT]), two cropping systems (cotton [Gossypium hirsutum L.]-cotton-corn [Zea mays L.] and rye [Secale cereale L.]/cotton-rye/cotton-corn), and two N fertilization sources and rates (0 and 100 kg N ha(-1) from NH(4)NO(3) and 100 and 200 kg N ha(-1) from poultry litter). Carbon fractions were soil organic C (SOC), particulate organic C (POC), microbial biomass C (MBC), and potential C mineralization (PCM). Crop residue varied among treatments and years and total residue from 1997 to 2005 was greater in rye/cotton-rye/cotton-corn than in cotton-cotton-corn and greater with NH(4)NO(3) than with poultry litter at 100 kg N ha(-1). The SOC content at 0 to 20 cm after 10 yr was greater with poultry litter than with NH(4)NO(3) in NT and CT, resulting in a C sequestration rate of 510 kg C ha(-1) yr(-1) with poultry litter compared with -120 to 147 kg C ha(-1) yr(-1) with NH(4)NO(3). Poultry litter also increased PCM and MBC compared with NH(4)NO(3). Cropping increased SOC, POC, and PCM compared with fallow in NT. Long-term poultry litter application or continuous cropping increased soil C storage and microbial biomass and activity compared with inorganic N fertilization or fallow, indicating that these management practices can sequester C, offset atmospheric CO(2) levels, and improve soil and environmental quality.     

Ammonia volatilization from marsh-pond-marsh constructed wetlands treating swine wastewater

Ammonia (NH3) volatilization is an undesirable mechanism for the removal of nitrogen (N) from wastewater treatment wetlands. To minimize the potential for NH3 volatilization, it is important to determine how wetland design affects NH3 volatilization. The objective of this research was to determine how the presence of a pond section affects NH3 volatilization from constructed wetlands treating wastewater from a confined swine operation. Wastewater was added at different N loads to six constructed wetlands of the marsh-pond-marsh design that were located in Greensboro, North Carolina, USA. A large enclosure was used to measure NH3 volatilization from the marsh and pond sections of each wetland in July and August of 2001. Ammonia volatilized from marsh and pond sections at rates ranging from 5 to 102 mg NH3-N m(-2) h(-1). Pond sections exhibited a significantly greater increase in the rate of NH3 volatilization (p < 0.0001) than did either marsh section as N load increased. At N loads greater than 15 kg ha(-1) d(-1), NH3 volatilization accounted for 23 to 36% of the N load. Furthermore, NH3 volatilization was the dominant (54-79%) N removal mechanism at N loads greater than 15 kg ha(-1) d(-1). Without the pond sections, NH3 volatilization would have been a minor contributor (less than 12%) to the N balance of these wetlands. To minimize NH3 volatilization, continuous marsh systems should be preferred over marsh-pond-marsh systems for the treatment of wastewater from confined animal operations.     

Ammonia volatilization from surface-applied poultry litter under conservation tillage management practices

Land application of poultry litter can provide essential plant nutrients for crop production, but ammonia (NH(3)) volatilization from the litter can be detrimental to the environment. A multiseason study was conducted to quantify NH(3) volatilization rates from surface-applied poultry litter under no-till and paraplowed conservation tillage managements. Litter was applied to supply 90 to 140 kg N ha(-1). Evaluation of NH(3) volatilization was determined using gas concentrations and the flux-gradient gas transport technique using the momentum balance transport coefficient. Ammonia fluxes ranged from 3.3 to 24% of the total N applied during the winter and summer, respectively. Ammonia volatilization was rapid immediately after litter application and stopped within 7 to 8 d. Precipitation of 17 mm essentially halted volatilization, probably by transporting litter N into the soil matrix. Application of poultry to conservation-tilled cropland immediately before rainfall events would reduce N losses to the atmosphere but could also increase NO(3) leaching and runoff to streams and rivers.     

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.     

Cattle feedlot soil moisture and manure content: I. Impacts on greenhouse gases, odor compounds, nitrogen losses, and dust

Beef cattle feedlots face serious environmental challenges associated with manure management, including greenhouse gas, odor, NH3, and dust emissions. Conditions affecting emissions are poorly characterized, but likely relate to the variability of feedlot surface moisture and manure contents, which affect microbial processes. Odor compounds, greenhouse gases, nitrogen losses, and dust potential were monitored at six moisture contents (0.11, 0.25, 0.43, 0.67, 1.00, and 1.50 g H2O g(-1) dry matter [DM]) in three artificial feedlot soil mixtures containing 50, 250, and 750 g manure kg(-1) total (manure + soil) DM over a two-week period. Moisture addition produced three microbial metabolisms: inactive, aerobic, and fermentative at low, moderate, and high moisture, respectively. Manure content acted to modulate the effect of moisture and enhanced some microbial processes. Greenhouse gas (CO2, N2O, and CH4) emissions were dynamic at moderate to high moisture. Malodorous volatile fatty acid (VFA) compounds did not accumulate in any treatments, but their persistence and volatility varied depending on pH and aerobic metabolism. Starch was the dominant substrate fueling both aerobic and fermentative metabolism. Nitrogen losses were observed in all metabolically active treatments; however, there was evidence for limited microbial nitrogen uptake. Finally, potential dust production was observed below defined moisture thresholds, which were related to manure content of the soil. Managing feedlot surface moisture within a narrow moisture range (0.2-0.4 g H2O g(-1) DM) and minimizing the accumulation of manure produced the optimum conditions that minimized the environmental impact from cattle feedlot production.     

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.     

Nitrogen loss through lateral seepage in near-trench paddy fields

A near-trench paddy field experiment with five urea application rates (0-360 kg N ha(-1) in 90-kg increments) was conducted on a paddy soil in the Taihu Lake Region of China to elucidate N losses through lateral seepage during three rice (Oryza sativa L.) growing seasons. The total N (Nt), NH4(+) -N, and NO3(-) -N concentrations in the lateral seepage water increased with increasing N rates. The seasonal Nt fluxes by lateral seepage varied from 6.8 to 25.6 kg N ha(-1) for urea application rates of 90 to 360 kg N ha(-1). Lateral seepage accounted for 4.7 to 6.6% of the Nt applied, implying that lateral seepage was an important pathway of N loss from near-trench paddy fields. The cumulative N loss via lateral seepage was significantly related to N fertilization rate (P = 0.05). Floodwater level was also identified as a main factor affecting N losses via lateral seepage from paddy fields, as indicated by a positive linear relationship (R2 = 0.43) between floodwater level and daily lateral flow during the flooded period (P = 0.05). Under the conditions of these experiments, a shallow floodwater depth of 50 mm, urea application rates of 90 kg N ha(-1) or less, and no rainfall within 1 wk after N application reduced N losses by lateral seepage from paddy fields.     

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.     

Ammonia emission factors from broiler litter in barns, in storage, and after land application

We measured NH? emissions from litter in broiler houses, during storage, and after land application and conducted a mass balance of N in poultry houses. Four state-of-the-art tunnel-ventilated broiler houses in northwest Arkansas were equipped with NH? sensors, anemometers, and data loggers to continuously record NH? concentrations and ventilation for 1 yr. Gaseous fluxes of NH?, N?O, CH?, and CO? from litter were measured. Nitrogen (N) inputs and outputs were quantified. Ammonia emissions during storage and after land application were measured. Ammonia emissions during the flock averaged approximately 15.2 kg per day-house (equivalent to 28.3 g NH?per bird marketed). Emissions between flocks equaled 9.09 g NH? per bird. Hence, in-house NH? emissions were 37.5 g NH? per bird, or 14.5 g kg(-1) bird marketed (50-d-old birds). The mass balance study showed N inputs for the year to the four houses totaled 71,340 kg N, with inputs from bedding, chicks, and feed equal to 303, 602, and 70,435 kg, respectively (equivalent to 0.60, 1.19, and 139.56 g N per bird). Nitrogen outputs totaled 70,396 kg N. Annual N output from birds marketed, NH? emissions, litter or cake, mortality, and NO? emissions was 39,485, 15,571, 14,464, 635, and 241 kg N, respectively (equivalent to 78.2, 30.8, 28.7, 1.3, and 0.5 g N per bird). The percent N recovery for the N mass balance study was 98.8%. Ammonia emissions from stacked litter during a 16-d storage period were 172 g Mg(-1) litter, which is equivalent to 0.18 g NH? per bird. Ammonia losses from poultry litter broadcast to pastures were 34 kg N ha (equivalent to 15% of total N applied or 7.91 g NH? per bird). When the litter was incorporated into the pasture using a new knifing technique, NH? losses were virtually zero. The total NH? emission factor for broilers measured in this study, which includes losses in-house, during storage, and after land application, was 45.6 g NH? per bird marketed.     

Chemical and physical changes following co-composting of beef cattle feedlot manure with phosphogypsum

Nitrogen (N) loss during beef cattle (Bos taurus) feedlot manure composting may contribute to greenhouse gas emissions and increase ammonia (NH(3)) in the atmosphere while decreasing the fertilizer value of the final compost. Phosphogypsum (PG) is an acidic by-product of phosphorus (P) fertilizer manufacture and large stockpiles currently exist in Alberta. This experiment examined co-composting of PG (at rates of 0, 40, 70, and 140 kg PG Mg(-1) manure plus PG dry weight) with manure from feedlot pens bedded with straw or wood chips. During the 99-d composting period, PG addition reduced total nitrogen (TN) loss by 0.11% for each 1 kg Mg(-1) increment in PG rate. Available N at the end of composting was significantly higher for wood chip-bedded (2180 mg kg(-1)) than straw-bedded manure treatments (1820 mg kg(-1)). Total sulfur (TS) concentration in the final compost increased by 0.19 g kg(-1) for each 1 kg Mg(-1) increment in PG rate from 5.2 g TS kg(-1) without PG addition. Phosphogypsum (1.6 g kg(-1) P) addition had no significant effect on total phosphorus (TP) concentration of the final composts. Results from this study demonstrate the potential of PG addition to reduce overall N losses during composting. The accompanying increase in TS content has implications for use of the end-product on sulfur-deficient soils. Co-composting feedlot manure with PG may provide an inexpensive and technologically straightforward solution for managing and improving the nutrient composition of composted cattle manure.     

Reduction of ammonia emission by shallow slurry injection: injection efficiency and additional energy demand

Ammonia (NH3) emission from livestock production causes undesirable environmental effects and a loss of plant-available nitrogen. Much atmospheric NH3 is lost from livestock manure applied in the field. The NH3 emission may be reduced by slurry injection, but slurry injection in general, and especially on grassland, increases the energy demand and places heavy demands on the slurry injection techniques used. The reduction in NH3 emission, injection efficiency, and energy demand of six different shallow slurry-injection techniques was examined. The NH3 emission from cattle slurry applied to grassland was reduced by all the injectors tested in the study, but there were major differences in the NH3 reduction potential of the different types of injectors. Compared with the trailing hose spreading technique, the NH3 loss was reduced by 75% when cattle slurry was injected using the most efficient slurry injection technique, and by 20% when incorporated by the least efficient injection technique. The reduction in NH3 emission was correlated with injection depth and the volume of the slot created. The additional energy demand for reducing ammonia emissions by slurry injection was approximately 13 000 kJ ha(-1) for a 20% reduction and 34 000 kJ ha(-1) for a 75% reduction. The additional energy demand corresponds to additional emissions of, respectively, 5.6 and 14.5 kg CO2 per ha injected.     

Management factors affecting ammonia volatilization from land-applied cattle slurry in the Mid-Atlantic USA

Ammonia (NH3) volatilization commonly causes a substantial loss of crop-available N from surface-applied cattle slurry. Field studies were conducted with small wind tunnels to assess the effect of management factors on NH3 volatilization. Two studies compared NH3 volatilization from grass sward and bare soil. The average total NH3 loss was 1.5 times greater from slurry applied to grass sward. Two studies examined the effect of slurry dry matter (DM) content on NH3 loss under hot, summer conditions in Maryland, USA. Slurry DM contents were between 54 and 134 g kg(-1). Dry matter content did not affect total NH3 loss, but did influence the time course of NH3 loss. Higher DM content slurries had relatively higher rates of NH3 volatilization during the first 12 to 24 h, but lower rates thereafter. Under the hot conditions, the higher DM content slurries appeared to dry and crust more rapidly causing smaller rates of NH3 volatilization after 12 to 24 h, which offset the earlier positive effects of DM content on NH3 volatilization. Three studies compared immediate incorporation with different tillage implements. Total NH3 loss from unincorporated slurry was 45% of applied slurry NH4+-N, while losses following immediate incorporation with a moldboard plow, tandem-disk harrow, or chisel plow were, respectively, 0 to 3, 2 to 8, and 8 to 12%. These ground cover and DM content data can be used to improve predictions of NH3 loss under specific farming conditions. The immediate incorporation data demonstrate management practices that can reduce NH3 volatilization, which can improve slurry N utilization in crop-forage production.     

Physical and chemical properties of feedlot pen surfaces located on moderately coarse- and moderately fine-textured soils in southern Alberta

Southern Alberta has the highest density of feedlot cattle in Canada, and there is a concern that leaching of water and contaminants may be greater for feedlots located on coarser-textured than finer-textured soils. Our objective was to determine if infiltration and leaching were greater for a 4-yr-old feedlot located on a moderately coarse-textured (MC) soil compared with two feedlots located on moderately fine-textured (MF) soils (5- and 52-yr-old pens). Various soil physical properties of feedlot pen surfaces were measured, including field-saturated hydraulic conductivity (K(fs)) and near-saturated hydraulic conductivity at -0.9 and -3.9 cm water potential. Selected chemical properties of feedlot soil layers were measured, as well as the chloride content of the soil profile (0-100 cm). Mean K(fs), K(-0.9), and K(-3.9) values were not significantly (P > 0.10) greater at the MC site than the two MF sites, indicating no evidence of greater infiltration on coarser-textured soils. In addition, mean K(fs), K(-0.9), and K(-3.9) values of soils within feedlot pens at all three sites were significantly (P < or = 0.10) reduced by 46 to 78% compared with soil outside the pens. Depth of chloride accumulation was greatest at the 52-yr-old feedlot on MF soil (60-70 cm), followed by 4-yr-old feedlot on MC soil (40-50 cm) and 5-yr-old feedlot on MF soil (30-40 cm). Visual inspection determined that the black interface layer formed within 2 mo of cattle stocking at all three sites.     

Gaseous nitrogen emissions and forage nitrogen uptake on soils fertilized with raw and treated swine manure

Treatments to reduce solids content in liquid manure have been developed, but little information is available on gaseous N emissions and plant N uptake after application of treated liquid swine manure (LSM). We measured crop yield, N uptake, and NH3 and N2O losses after the application of mineral fertilizer (NH4 NO3), raw LSM, and LSM that was decanted, filtered, anaerobically digested, or chemically flocculated. The experiment was conducted from 2001 to 2003 on a loam and a sandy loam cropped to timothy (Phleum pratense L.) with annual applications equivalent to 80 kg N ha(-1) in spring and 60 kg N ha(-1) after the first harvest. Raw LSM resulted in NH3 emissions three to six times larger (P < 0.05) than mineral fertilizer. The LSM treatments reduced NH3 emissions by an average of 25% compared with raw LSM (P < 0.05). The N2O emissions tended to be higher with raw LSM than with mineral fertilizer. The LSM treatments had little effect on N2O emissions, except for anaerobic digestion, which reduced emissions by >50% compared with raw LSM (P < 0.05). Forage yield with raw LSM was >90% of that with mineral fertilizer. The LSM treatments tended to increase forage yield and N uptake relative to raw LSM. We conclude that treated or untreated LSM offers an alternative to mineral fertilizers for forage grass production but care must be taken to minimize NH3 volatilization. Removing solids from LSM by mechanical, chemical, and biological means reduced NH3 losses from LSM applied to perennial grass.     

Ammonia emissions from field-simulated cattle defecation and urination

Atmospheric ammonia (NH(3)) is a concern because of its environmental impact. The greatest contribution to atmospheric NH(3) comes from agricultural sources. This study quantified NH(3) volatilization from cattle defecation and urination on pasture under field conditions in Auburn, Alabama. Treatments consisted of beef feces, dairy feces, dairy urine, and a control. The experiment was conducted during four seasons from June 2003 to April 2004. Fresh feces or urine was applied onto grass swards, and NH(3) volatilization was measured up to 14 d after application using an inverted chamber method. Dairy urine was the only significant source of NH(3). Ammonia nitrogen (N) loss differed among seasons, ranging from 1.8% in winter to 20.9% during the warmer summer months. Cumulative volatilization was best described in this experiment by the equation % NH(3)-N loss = N(max) (1 - e(-ct))(i). The highest rate of NH(3) volatilization generally occurred within 24 h. This study suggests that NH(3) volatilization from cattle urine on pasture is significant and varies with season, whereas NH(3) volatilization from cattle feces is negligible.     

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.     

Long-term effects of poultry litter, alum-treated litter, and ammonium nitrate on aluminum availability in soils

Research has shown that alum [Al(2)(SO(4))(3).14H(2)O] applications to poultry litter can greatly reduce phosphorus (P) runoff, as well as decrease ammonia (NH(3)) volatilization. However, the long-term effects of fertilizing with alum-treated litter are unknown. The objectives of this study were to evaluate the long-term effects of normal poultry litter, alum-treated litter, and ammonium nitrate (NH(4)NO(3)) on aluminum (Al) availability in soils, Al uptake by tall fescue (Festuca arundinacea Schreb.), and tall fescue yields. A long-term study was initiated in April of 1995. There were 13 treatments (unfertilized control, four rates of normal litter, four rates of alum-treated litter, and four rates of NH(4)NO(3)) in a randomized block design. All fertilizers were broadcast applied to 52 small plots (3.05 x 1.52 m) cropped to tall fescue annually in the spring. Litter application rates were 2.24, 4.49, 6.73, and 8.98 Mg ha(-1) (1, 2, 3, and 4 tons acre(-1)); NH(4)NO(3) rates were 65, 130, 195, and 260 kg N ha(-1) and were based on the amount of N applied with alum-treated litter. Soil pH, exchangeable Al (extracted with potassium chloride), Al uptake by fescue, and fescue yields were monitored periodically over time. Ammonium nitrate applications resulted in reductions in soil pH beginning in Year 3, causing exchangeable Al values to increase from less than 1 mg Al kg(-1) soil in Year 2 to over 100 mg Al kg(-1) soil in Year 7 for many of the NH(4)NO(3) plots. In contrast, normal and alum-treated litter resulted in an increase in soil pH, which decreased exchangeable Al when compared to unfertilized controls. Severe yield reductions were observed with NH(4)NO(3) beginning in Year 6, which were due to high levels of acidity and exchangeable Al. Aluminum uptake by forage and Al runoff from the plots were not affected by treatment. Fescue yields were highest with alum-treated litter (annual average = 7.36 Mg ha(-1)), followed by normal litter (6.93 Mg ha(-1)), NH(4)NO(3) (6.16 Mg ha(-1)), and the control (2.89 Mg ha(-1)). These data indicate that poultry litter, particularly alum-treated litter, may be a more sustainable fertilizer than NH(4)NO(3).     

Residual soil nitrate after potato harvest

Nitrogen loss by leaching is a major problem, particularly with crops requiring large amounts of N fertilizer. We evaluated the effect of N fertilization and irrigation on residual soil nitrate following potato (Solanum tuberosum L.) harvests in the upper St-John River valley of New Brunswick, Canada. Soil nitrate contents were measured to a 0.90-m depth in three treatments of N fertilization (0, 100, and 250 kg N ha(-1)) at two on-farm sites in 1995, and in four treatments of N fertilization (0, 50, 100, and 250 kg N ha(-1)) at four sites for each of two years (1996 and 1997) with and without supplemental irrigation. Residual soil NO3-N content increased from 33 kg NO3-N ha(-1) in the unfertilized check plots to 160 kg NO3-N ha(-1) when 250 kg N ha(-1) was applied. Across N treatments, residual soil NO3-N contents ranged from 30 to 105 kg NO3-N ha(-1) with irrigation and from 30 to 202 kg NO3-N ha(-1) without irrigation. Residual soil NO3-N content within the surface 0.30 m was related (R2 = 0.94) to the NO3-N content to a 0.90-m depth. Estimates of residual soil NO3-N content at the economically optimum nitrogen fertilizer application (Nop) ranged from 46 to 99 kg NO3-N ha(-1) under irrigated conditions and from 62 to 260 kg NO3-N ha(-1) under nonirrigated conditions, and were lower than the soil NO3-N content measured with 250 kg N ha(-1). We conclude that residual soil NO3-N after harvest can be maintained at a reasonable level (<70 kg NO3-N ha(-1)) when N fertilization is based on the economically optimum N application.