Limitations of the electronic capacitance meter in measuring yields of grazed tropical pastures

Abstract

AbstractRelationships between readings of the electronic (capacitance) pasture meter and descriptions of pasture yield were examined over the yearly growth cycle in grazed pastures of Setaria anceps cv. Nandi, with or without Macroptilium atropurpurem cv. Siratro and Desmodium intortum cv. Greenleaf. There was a poor relationship between meter reading and pasture dry matter yield (r =+0.574 pooled over pastures and seasons) but this relationship was improved to r=+0.750 by inclusion of other regressors describing pasture height and proportion of inert material. Meter reading was more closely related to fresh pasture yield (r =+0.830), water yield (r =+0.885) or dried green yield (r =+0.830), although inclusion of a pasture height term still improved the relationship slightly. Suggestions are made about using the meter to estimate dried green yield rather than total dry matter yield, and taking more consideration of the proportion of inert material when relating the meter reading to total dry matter yield.Visual estimation was also compared with actual pasture yield measured by cutting. Even though prior training for yield estimation was inadequate, the relationships between visually estimated and actual yield were as good as those from the pasture meter. It is concluded that the pasture meter will not find a regular use as a sampling tool in most grazed tropical pastures.