THE EFFECT OF INCREASING WINDS ON THE DISTRIBUTION OF OVERSOWN SEED AND FERTILISER

Abstract

Distribution patterns of white clover, perennial ryegrass and cocksfoot were measured when oversown with granulated superphosphate in contrasting cross wind speeds, under both airfield and hill country conditions. Increasing velocity of cross wind reduced the variability of spread of all components. Swath width increased, and maximum seed rate declined, with increasing cross wind. Some separation of seed types occurred, with the tighter fractions being moved further downwind. Measured distribution patterns from single flights were used to estimate paddock scale applications by overlapping swaths at normal flight path spacings for a Fletcher FU24-950 aircraft (12 m centres). The proportion of land receiving less than half the target application rate declined from 50%, under near calm conditions, to nil, under conditions of medium cross winds (e.g. l0-12 km/h). Wind is therefore a desirable factor during oversowing operations and significantly reduces variability of overall distribution. Keywords: hill country. superphosphate, PAPR, oversowing, topdressing