Herbage measurement in situ by electronics. 1. The multiple‐probe‐type capacitance meter: a brief review

The history and development of the multiple‐probe capacitance meter used for in situ, non‐destructive estimations of herbage mass is reviewed. An elementary, semi‐theoretical electric‐field analysis focuses attention on the inherent difficulties associated with the multiple‐probe approach. This report establishes the background for the introduction of an ‘earth‐plate’ capacitancemeter.