Agroscope, Institute for Plant Production Sciences IPS, 1260 Nyon, Switzerland

Estimation of herbage yield based on sward height

Sward height measurements were made on a variety of Swiss grassland plots in 1997-98. Between values measured with a French and a New Zealand rising plate meter (RPM), very good correlation was found whereas it was less strong with ruler measurements. For two different grassland types, regression analysis was applied to estimate dry matter (DM) yield using vegetation height. Equations differed considerably between herbage types, but also between years for the same plot. Height and yield measurements also give evidence that lower cutting leads to shorter and denser regrowth. At one location (La Frêtaz) sward density (kg DM/ha/ cm) declined strongly during the season. Therefore, when height measurements are converted into yield estimates, there should be sufficient differentiation for measuring conditions. However, the rising plate meter is appropriate for the determination of grass growth curves and as an aid to better pasture management in terms of time and area.

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