Ammonia volatilization from pig slurry applied with trail hoses or broadspread to winter wheat: Effects of crop developmental stage, microclimate, and leaf ammonia absorption

A micrometeorological mass balance technique was used to determine ammonia (NH3) volatilization from pig (sus scrofa) slurry applied to winter wheat (Triticum aestivum Lam.). The slurry was applied with trail hoses on the soil below the canopy or by a splash plate technique spreading the slurry on both plants and soil. The two application techniques were compared in parallel experiments of 7 d duration on each of nine occasions in the period from April 1993 to June 1995. The loss of NH3 varied from 4 to 26% of the ammonium (NH4+) in slurry applied with trail hoses and from 11 to 26% when applied with splash plates. Trail hose application reduced NH3 volatilization by up to 80% compared with the losses from splash plate applied slurry. The greatest reduction was observed when slurry was applied to a tall and dense crop, while the trail hose technique did not reduce losses when slurry was applied to a 10 cm high crop with a leaf area index of 0.3. The decreasing NH3 volatilization with increasing crop height was due to a reduced wind speed above the slurry surface, promoted slurry infiltration due to increased drying of the top soil and increasing leaf absorption of volatilized NH3. Wind speed and air temperature above the canopy and the chemical composition of the slurry had little influence on NH3 volatilization from trail hose applied slurry. On the contrary, these factors increased NH3 volatilization from splash plate applied slurry. The NH3 volatilized from trail hose applied slurry was absorbed by the wheat plants in rates from 0 to 0.74 g NH3-N m(-2) leaf surface during a period of 7 d after slurry application. Canopy NH3 absorption was responsible for up to 25% of the reduction in NH3 loss when using trail hose application. The wheat plants did not absorb NH3 during stent elongation in the vegetative growth period.