Estimating Ammonia Volatilization from Swine-Effluent Droplets in Sprinkle Irrigation

homa State University Research Station in Goodwell, OK to measure volatilization losses of ammoniacal N Irrigation of swine effluent is one of the most economical ways to from swine-effluent applied to the land surface by flood dispose of swine manure. The determination of appropriate application rates requires the quantification of volatilization losses of ammoirrigation. Wu et al. (2003) developed a mechanistic niacal N. In this research, a mechanistic model was developed to model to predict N transport in a soil profile and ammoestimate droplet volatilization loss (excluding drift losses) of ammoninia volatilization from liquid and soil surfaces. The simuacal N from swine effluent in sprinkler irrigation. Field experiments lated ammonia-volatilization rate and cumulative volawere conducted to validate the model. The model combined energy tilization from the model agreed well with the measured balance, mass balances of ammoniacal N, and water to predict equilibdata from the flood irrigation experiments. A major rium temperature of a droplet, and losses of ammoniacal N and water purpose of the mechanistic model is to predict ammonia from a droplet. Trajectory analysis was employed in the model to esvolatilization under the condition of sprinkler irrigation timate a droplet’s exposure time in air. Mass and heat transfer coeffiusing parameters from field experiments with flood irricients developed in boundary layer theory were incorporated in the gation. In sprinkler irrigation losses from droplet volatilmass and energy balance equations to predict fluxes of heat, ammoniacal N, and water. Equilibrium constants of transformation reactions ization, wind drift, and canopy interception are in addiwere used in the model to establish relationships among component tion to soil-surface volatilization loss with flood species of ammoniacal N. Field experiments measured concentrations irrigation. Losses from wind drift and canopy intercepof ammoniacal N in swine-effluent samples collected at the nozzles tion represent the portion of volatilization losses from and ground surface to determine the loss of ammoniacal N caused droplets falling outside the targeted area while the losses by droplet volatilization. The measured concentration decreases were from droplet volatilization and soil-surface volatilizacombined with water loss percentages to estimate percentage losses of tion represent the portion of losses from droplets falling ammoniacal N. Results from both field experiment and mathematical on the irrigated area. Droplet volatilization and soilmodeling indicated that loss of ammoniacal N from droplet volatilizasurface volatilization occur before and after the on-tartion was only a few percentages which was considered insignificant get droplets hit the ground. Losses from wind drift and compared with common soil surface volatilization loss of 20 to 50% at the end of 1 wk after application. canopy interception can be evaluated directly from estimations of water losses. They are the amount of water losses multiplied by the initial concentration of ammoniacal N in the effluent. Methods for estimating the M of animal wastes from animal conamount of water losses from wind drift and canopy finement facilities is a very important issue in interception were developed by irrigation scientists and swine and poultry farming. If inadequately handled, anihydrologists (Brooks et al., 1991; Keller and Bliesner, mal manure poses a significant threat to the quality of 1990; van Dijk and Bruijnzeel, 2001a,b). air and water nearby the storage and disposal areas. Pote et al. (1980) developed a numerical model to When properly managed, animal manure is a valuable estimate ammonia volatilization from a droplet during source of fertilizer for crop production. Swine-effluent its exposure time (i.e., the interval from the time a dropirrigation is considered one of the most economic ways let leaves a sprinkler nozzle to the time it hits the of swine-manure disposal (Zhang and Hamilton, 2000). ground). However, the model ignored the temperature One of the key issues in swine-effluent irrigation is the dependence of the equilibrium constant, Ka, in the NH3 determination of a proper application rate because (aq) ↔ NH 4 (aq) reaction, and therefore, may not be applying lagoon effluent at a rate exceeding the limit applicable for temperatures significantly different from of the growing crop’s N need may cause nitrate leaching 25 C. In this research, we developed an analytical model to ground water. The amount of ammoniacal N added to predict droplet concentration of ammoniacal N at to a soil system from a swine-effluent-irrigation event different times and to evaluate the volatilization loss of is dependent on the initial amount of ammoniacal N in ammonia from a droplet. The model was derived from the effluent applied and the losses of ammoniacal N mass balance of ammoniacal N in a droplet and incorpoduring the irrigation event. Zupancic et al. (1999) and rated temperature dependence of the transport and reWarren (2001) conducted field experiments at the Oklaaction parameters. Energy balance and mass balance of water were also incorporated into the model to preDep. of Plant and Soil Sciences, Oklahoma State Univ., Stillwater, dicted equilibrium temperature of a droplet and evapoOK 74078. This research was supported in part by funds from the ration loss of water, which were needed for evaluating Oklahoma Agricultural Experiment Station and from CSREES Projvolatilization loss of ammonia. Mass and heat transfer ect Number OKL02445. Received 19 Aug. 2002. *Corresponding author ([email protected]). coefficients developed from boundary layer theory (Incropera and DeWitt, 1990) were used in the mass and Published in Soil Sci. Soc. Am. J. 67:1352–1360 (2003).  Soil Science Society of America 677 S. Segoe Rd., Madison, WI 53711 USA Abbreviations: LDN, low drift nozzle.