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 amm onia (NH3) volatilization from pig (sus scrofa) slurry applied to wint er wheat (Triticum aestivum Lam.). The slurry was applied with trail h oses on the soil below the canopy or by a splash plate technique sprea ding the slurry on both plants and soil. The two application technique s were compared in parallel experiments of 7 d duration on each of nin e occasions in the period from April 1993 to June 1995. The loss of NH 3 varied from 4 to 26% of the ammonium (NH4+) in slurry applied with t rail hoses and from 11 to 26% when applied with splash plates. Trail h ose application reduced NH3 volatilization by up to 80% compared with the losses from splash plate applied slurry. The greatest reduction wa s 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 v olatilization with increasing crop height was due to a reduced wind sp eed above the slurry surface, promoted slurry infiltration due to incr eased drying of the top soil and increasing leaf absorption of volatil ized NH3. Wind speed and air temperature above the canopy and the chem ical composition of the slurry had little influence on NH3 volatilizat ion from trail hose applied slurry. On the contrary, these factors inc reased NH3 volatilization from splash plate applied slurry. The NH3 vo latilized from trail hose applied slurry was absorbed by the wheat pla nts 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 responsibl e for up to 25% of the reduction in NH3 loss when using trail hose app lication. The wheat plants did not absorb NH3 during stent elongation in the vegetative growth period.