ESTIMATING AMMONIA VOLATILIZATION FROM UNSATURATED UREA FERTILIZED AND URINE AFFECTED SOILS BY AN INDIRECT METHOD

An indirect method for evaluating the emission of ammonia from urea-fe rtilized upland crops or urine-affected pastures, without affecting th e plant's environment, was evaluated at Yanco, N.S.W., Australia and n ear Lincoln University, New Zealand. The parameters measured were the ammoniacal nitrogen concentration, pH and temperature in the aqueous p hase at the soil's surface, and windspeed at a reference height. The c ombined effect of these influences on volatilization rate were incorpo rated into a linear relationship of the form F = k U-z rho(o), where F is the vertical flux of ammonia, determined by a micrometeorological method, U-z is the wind speed at some reference height above the soil, po is the ammonia concentration in equilibrium with the liquid phase (calculated from the ammoniacal nitrogen concentration, pH and tempera ture) and k is a proportionality constant. Strong linear relationships of this kind were found for the data sets from both experiments. The respective correlation coefficients for the relationships at the two s ites were 0.870 and 0.879, and the respective k values were 6.3 x 10(- 5) and 7.5 x 10(-5). The field measurements require little in the way of specialized equipment (e.g. flat - surface pH electrode, ammonia el ectrode, anemometer) and are comparatively easy to carry out. The resu lts suggest that with some further refinement, this technique could ac hieve application in the calculation of ammonia losses from small plot s in the field.