Summary -ZusammenfassungField experiments under various conditions were carried out in Hohenheim and the Allgiu t o measure the effects of liquid manure properties and meteorological factors on ammonia losses. The micrometeorological method ( I H F ) and the wind tunnel method were used.Depending on the prevailing conditions the ammonia losses varied between 14 and YYVin of the applied ammonium nitrogen.The relationship between the ammonia loss and the logarithm of the dry matter content of' liquid manure was highly significant. The dry matter

A wind tunnel was constructed for measurement of NH3− N volatilization after application of liquid manure. It combines the advantages of micrometeorological field methods with those of customary wind tunnel methods. The wind tunnel, as specified in part I (Braschkat et al., 1993), is characterized by: ‐the same (or higher) reliability of results as in field measurement by the IHF method (Integrated Horizontal Flux, also known as Mass Balance) ‐universal applicability independent of topographical conditions ‐a higher temporal and spatial density of experiments compared to micrometeorological methods The reliability of the NH3− N measurements obtained by the wind tunnel was tested under controlled conditions in a greenhouse (calibration) as well as under field conditions by direct comparison with the IHF method. The rate of recovery of NH3− N inserted into the wind tunnel is almost 100 % (± 3 %). In field experiments, no differences between the measurements of the wind tunnel and the IHF method were observed under standard conditions. The higher precision in the determination of the NH3− N background concentration with the wind tunnel resulted in a higher accuracy in measurements of the time course of NH3− N emissions. Intensity and timing of precipitation may cause an overestimation of NH3− N volatilization by the wind tunnel. In contrast to the IHF method. NH3− N emissions can be measured with the wind tunnel at wind speeds below 1 m s−1 at 2 m height. No reliable data were obtained with the wind tunnel at wind speeds below 0.3 m s−1 in 0.3 m height.

A windtunnel system is presented applicable for measuring ammonia emissions under field conditions. With this system two objectives are achieved: No alteration of the microclimatic conditions in the testing area Reliable determination of the volumetric air flow and the ammonia concentration The use of a transparent foil, the precise adjustment of the flow velocity to the windspeed outside, and the constant cross‐sectional area over the whole length of the tunnel are the most important constructional details of the system.

Field studies of the oilseed crops canola, Indian mustard, and linseed/Linola were conducted over 2 seasons at 2 contrasting sites in the cropping regions of central and southern NSW to determine the uptake of mineral nutrients and quantities removed in seed. The sites were in the Junee region where production of these oilseeds is common, and at Condobolin, which is regarded as marginal for production of the crops. The 2 rates of nitrogen (N) fertiliser applied were either none or rates that growers in the Condobolin and Junee regions would apply to achieve high seed yields after a cereal crop in the rotation when soil mineral N is low. Concentrations of total N, the major cations (K, Ca, Mg, Na) and major anions (P, S, Cl), and the micronutrients Fe, Mn, Zn, and Cu were determined in shoots harvested at flowering and maturity. Nitrate and sulfate were also measured, and estimates were made of excess cation concentrations in the plant material. The ranges of concentrations of excess cations in shoots of the oilseeds at flowering were 83–206 cmolc/kg and 43–121 cmolc/kg for straw at maturity. Linola had lower concentrations of excess cations in vegetative material (83–108 and 43–82 cmolc/kg at flowering and maturity, respectively) than canola or Indian mustard. Concentrations of excess cations in seed of the crops were lower than for vegetative material, and ranged from 30 to 49 cmolc/kg. Nitrogen fertiliser had relatively little effect on concentrations of mineral nutrients or excess cations in either shoots at flowering and maturity, or in seed. However, N fertiliser increased the growth and seed yields of the crops, and thus the amounts of mineral nutrients and excess cations in shoots and seed. The results are discussed in the context of the depletion of soil nutrients due to their removal in harvested seed of the N-fertilised crops. The contribution of excess cation removal in seed to soil acidification is also discussed. It is estimated that the quantity of lime required to neutralise the acidity resulting from removal of 1 t seed is 22.4 kg for canola, 17.0 for Indian mustard, and 20.8 for linseed/Linola. Estimates of the relative contributions of seed removal and N fertiliser to soil acidification are presented.

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