Ammonia volatilization from arable land after application of catt'e slurry. 1. Field estimates

Cattle slurry was surface-applied to bare soil in two experiments in the period September­ November 1987, while in April-May 1988 two experiments were carried out in which the slur­ ry was mixed with the upper 6 an of the soil with a cultivator immediately after spreading. The 1987 experiments both lasted 18 days, the 1988 experiments 9 days. A micrometcorologi· cal technique, which did not disturb the dynamics of the air flow, was employed for the NH) volatilization measurements. In addition, volatilization. losses were determined in­ directly from mineral-N contents of soil/slurry samples collected at intervals after applica· tion.~ Diurnal fluctuations in the NH) flux occurred throughout the experimental period, with maxima around midday and minima at midnight. The magnitude of the daily flux values decreased with time. The amounts of N lost through volatilization from surface·applied cattle slurry were 18 and 33 "0 of the total N, respectively, during the first 9 days, corresponding to 32 and 67 If. of the ammoniacal N applied with the slurry. Volatilization became negligible after day 9.lncor­ paration of the slurry into the soil considerably decreased the loss of N through volatilization: volatile losses of N after 9 days amounted to 6 and 7 01. of the total N, which corresponds to 11 and 16 .,. of the ammoniacal N applied with the slurry.