Modelling ammonia volatilization from animal slurry applied with trail hoses to cereals

In Europe ammonia (NH3), volatilization from animal manure is the major sou rce of NH3 in the atmosphere. From March to July 1997, NH3 volatilization f rom trail hose applied slurry was measured for seven days after application in six experiments. A statistical analysis of data showed that NH3 volatil ization rate during the first 4-5 h after slurry application increased sign ificantly (P < 5%) with wind speed and soil slurry surface water content. N H3 volatilization in the six measuring periods during the experiments incre ased significantly (P ( 5%) with relative water content of the soil slurry surface, global radiation, pH, and decreased with increasing rainfall durin g each measuring period and rainfall accumulated from onset of each experim ent. A mechanistic model of NH3 volatilization was developed. Model inputs are climate variables, soil characteristics and total ammoniacal nitrogen(T AN = ammonium + ammonia) in the soil surface layer. A pH submodel for predi cting pH at the surface of the soil slurry liquid was developed. The measur ed NH3 volatilization was compared with model simulations. The simulated re sults explained 27% of the variation in measured NH, volatilization rates d uring all seven days, but 48% of measured volatilization rates during the f irst 24h. Calculations with the model showed that applying slurry in the mo rning or in the afternoon reduced volatilization by 50% compared with a noo n application. Spreading the slurry with trail hoses to a 60 cm high crop r educed losses by 75% compared with a spreading onto bare soil. Ammonia vola tilization was 50% lower when the soil had dried out after slurry applicati on compared with a wet slurry surface. (C) 2000 Elsevier Science Ltd. All r ights reserved.