OPEN-AIR FUMIGATION OF FIELD CROPS - CRITERIA AND DESIGN FOR A NEW EXPERIMENTAL SYSTEM

The criteria for designing open-air systems to expose field crops to gaseous air pollutants were examined. A computer simulation of gas dispersion was then used to investigate the distribution of gas concentration produced by different source patterns and to develop a new design which permitted a spatially uniform exposure of an experimental area. A system constructed to the new design has been operated to fumigate winter cereals with sulphur dioxide throughout two complete growing seasons. Rates of gas release were controlled by a small computer to follow Predetermined patterns of concentration, and spatial uniformity of exposure was achieved. Effective control of concentration was demonstrated with examples of how frequency distributions of concentration and diurnal patterns can be reproduced experimentally.