An Improved Electronic Instrument for Estimation of Pasture Yield

Abstract

CAMPBELL et al.¹ have described an electronic instrument which can be used to estimate the yield of pasture in situ. The change in electrical capacitance of a probe, which is placed on the pasture, is converted to an audio frequency, This is in effect the difference in frequency between a valve oscillator attached to the probe and a transistor oscillator held by the operator. Both oscillators are initially set to about 3 Mc/s. Calibration was carried out for 15 sward types. The capacitance change was related by linear regression to the yield of fresh, dry and organic matter. Within types the instrument reading accounted for approximately 90 per cent of the variation in yield. Significant differences were found to exist, however, between the sward types. It was considered that the use of an overall linear regression for the estimation of fresh, dry or organic matter yield would lead to biased estimates for any particular sward type.