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In rapidly changing conditions repeated calibration of the pasture disc meter is necessary for reasonably accurate estimates of standing forage. Estimates of dry matter yield determined from the disc height of the meter depend on many factors, mainly disc height but also the moisture and fibre contents of the herbage and the degree to which it has been trampled. Daily calibration of the disc meter will automatically take care of these factors but this takes time. Five other methods for describing the changes in dry matter yield with time are discussed: two are multiple regressions with dry mass dependent on disc height, moisture and fibre content and a dummy variate for factors such as trampling and fouling. The use of a multiple regression, which is less laborious than repeated calibration, gave a reasonably accurate estimation of the dry matter yield and time relationship in rapidly changing conditions.