Alternative N fertilizers that produce low greenhouse gas (GHG) emissions from soil are needed to reduce the impacts of agricultural practices on global warming potential (GWP). We quantified and compared growing season fluxes of NO, CH, and CO resulting from applications of different N fertilizer sources, urea (U), urea-ammonium nitrate (UAN), ammonium nitrate (NHNO), poultry litter, and commercially available, enhanced-efficiency N fertilizers as follows: polymer-coated urea (ESN), SuperU, UAN + AgrotainPlus, and poultry litter + AgrotainPlus in a no-till corn ( L.) production system. Greenhouse gas fluxes were measured during two growing seasons using static, vented chambers. The ESN delayed the NO flux peak by 3 to 4 wk compared with other N sources. No significant differences were observed in NO emissions among the enhanced-efficiency and traditional inorganic N sources, except for ESN in 2009. Cumulative growing season NO emission from poultry litter was significantly greater than from inorganic N sources. The NO loss (2-yr average) as a percentage of N applied ranged from 0.69% for SuperU to 4.5% for poultry litter. The CH-C and CO-C emissions were impacted by environmental factors, such as temperature and moisture, more than the N source. There was no significant difference in corn yield among all N sources in both years. Site specifics and climate conditions may be responsible for the differences among the results of this study and some of the previously published studies. Our results demonstrate that N fertilizer source and climate conditions need consideration when selecting N sources to reduce GHG emissions.

proximately 70% of the broiler chickens produced nationally in 1999 were produced in Arkansas, Georgia, Temperate forages are used throughout the southeastern USA to Alabama, Mississippi, North Carolina, Texas, Tennesprovide feed for livestock when tropical and subtropical grasses are dormant and as a hay source. Long-term utilization of broiler litter see, and South Carolina (Natl. Agric. Statistics Serv., as a fertilizer in some areas of the region has elevated soil levels of 1999). A large proportion of the litter (a mixture of P and micronutrients. Our objective was to compare P, Cu, and Zn manure, wasted feed, feathers, and wood shavings or uptake among temperate forage species from a Savannah fine sandy other crop residue) is applied to hay fields and pastures. loam soil (fine-loamy, siliceous, semiactive, thermic Typic Fragiudult) Litter application may occur anytime during the year, amended with litter under a single-harvest system. Dry weight of depending on when a flock is removed from the house. ryegrass (Lolium multiflorum Lam.) herbage was greater than all If litter is applied to a dormant perennial or dead annual other species except ball clover (Trifolium nigrescens Viv.) in 1997 and tropical grass hay field or pasture during the winter and oat (Avena sativa L.) in 1998. Clovers were susceptible to Sclerotinia spring, the presence of an actively growing temperate crown and stem rot (Sclerotinia trifoliorum Erikss.) that reduced forage will reduce the potential for P loss, largely by plant density, vigor, and dry herbage weight. Although forage P concentration of all species was similar to or greater than ryegrass, only reducing sediment movement in runoff (Sharpley et crimson clover (T. incarnatum L.) had P uptake equal to ryegrass al., 1994). during both years (mean of 23.4 kg ha Ϫ1 ). This was attributed to the Frequent litter application also contributes to the achigh correlation between dry herbage weight and P uptake (r ϭ 0.95 cumulation of P and metals in the soil such as Cu and and 0.89 in 1997 and 1998, respectively). Legumes typically had greaterZn, which are added to poultry diets to improve weight Cu and Zn concentrations than ryegrass, but only crimson clover and gain and prevent diseases (Han et al., 2000). A benefit hairy vetch (Vicia villosa Roth) had comparatively greater Cu and of utilizing temperate species is that when harvested for Zn uptake during both years. The combination of desirable agronomic hay, they provide a means of exporting these minerals traits and nutrient uptake capacity make annual ryegrass a superior from fields where manure is applied (Brink and Rowe, temperate forage species for use in southeastern pastures fertilized 1999). Temperate forages can thus serve in both a feed with broiler litter. and nutrient management role (Daniel et al., 1998) in hay and pasture systems receiving broiler litter as a fertilizer source.

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Land application of poultry litter provides essential nutrients for hybrid bermudagrass [Cynodon dactylon (L.) Pers.] production, but ammonia (NH 3) volatilization and N mineralization influence the amount of litter N available for plant uptake. Our objective was to determine the combination of broiler litter and fertilizer N, which maximizes the yields of forage and N, P, and K by 'Coastal' bermudagrass. Studies were conducted for 3 yr (1999-2001) in pastures at Newton and Mize, MS that differed widely in soil test P (STP) due to history of litter application (0 vs. 301 yr, respectively.). Litter rates of 0, 4.5, 8.9, 13.4, and 17.9 Mg ha 21 were obtained by up to four monthly (April-July) applications of 4.5 Mg ha 21 and were supplemented with ammonium nitrate (NH 4-NO 3) to provide the same total N in each treatment. At Newton, combining litter with fertilizer N increased forage yield by 10% in 1999, 25% in 2000, and 34% in 2001, as compared to fertilizer N. At Mize, K uptake increased as litter rate increased in 2001 only. These responses to litter were related to increased soil P and K at Newton, and increased soil N, P, and Ca at Mize. Averaged across years, maximum P uptake of about 40 kg ha 21 was obtained by applying 8.9 Mg litter 1 134 kg N ha 21 at Newton and 4.5 Mg litter 1 202 kg N ha 21 at Mize. Safe and effective management of major plant nutrients in broiler litter may require the use of commercial N fertilizer.

Microbial populations within poultry litter have been largely ignored with the exception of potential human or livestock pathogens. A better understanding of the community structure and identity of the microbial populations within poultry litter could aid in the development of management practices that would reduce populations responsible for toxic air emissions and pathogen incidence. In this study, poultry litter air and physical properties were correlated to shifts in microbial community structure as analyzed by principal component analysis (PCA) and measured by denaturing gradient gel electrophoresis (DGGE). Litter samples were taken in a 36-point grid pattern at 5 m across and 12 m down a 146 m x 12.8 m chicken house. At each sample point, physical parameters such as litter moisture, pH, air and litter temperature, and relative humidity were recorded, and samples were taken for molecular analysis. The DGGE analysis showed that the banding pattern of samples from the back and water/feeder areas of poultry house were distinct from those of samples from other areas. There were distinct clusters of banding patterns corresponding to the front, middle front, middle back, back, and waterer/feeder areas. The PCA analysis showed similar cluster patterns, but with more distinct separation of the front and midhouse samples. The PCA analysis also showed that moisture content and litter temperature (accounting for 51.5 and 31.5% of the separation of samples, respectively) play a major role in spatial diversity of microbial community in the poultry house. Based on analysis of DGGE fingerprints and cloned DGGE band sequences, there appear to be differences in the types of microorganisms over the length of the house, which correspond to differences in the physical properties of the litter.

Poultry litter provides a rich nutrient source for crops, but the usual practice of surface-applying litter can degrade water quality by allowing nutrients to be transported from fields in surface runoff while much of the ammonia (NH3)-N escapes into the atmosphere. Our goal was to improve on conventional titter application methods to decrease associated nutrient losses to air and water while increasing soil productivity. We developed and tested a knifing technique to directly apply dry poultry litter beneath the surface of pastures. Results showed that subsurface litter application decreased NH3-N volatilization and nutrient losses in runoff more than 90% (compared with surface-applied litter) to levels statistically as low as those from control (no litter) plots. Given this success, two advanced tractor-drawn prototypes were developed to subsurface apply poultry litter in field research. The two prototypes have been tested in pasture and no-till experiments and are both effective in improving nutrient-use efficiency compared with surface-applied litter, increasing crop yields (possibly by retaining more nitrogen in the soil), and decreasing nutrient losses, often to near background (control plot) levels. A paired-watershed study showed that cumulative phosphorus losses in runoff from continuously grazed perennial pastures were decreased by 55% over a 3-yr period if the annual poultry litter applications were subsurface applied rather than surface broadcast. Results highlight opportunities and challenges for commercial adoption of subsurface poultry litter application in pasture and no-till systems.

potential for decreasing the amount of symbiotic N 2 fixation. In contrast, Lory et al. (1992) reported that Although most of the N required by soybean [Glycine max (L.) topdressed manure addition to alfalfa (Medicago sativa L.)

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