Influence of fertiliser and grazing management on North Island moist hill country 4. Pasture species abundance

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Abstract
A grazing trial was conducted on steep, moist, low fertility hill country in the southern Hawke's Bay during 1975–81. There were 2 fertiliser treatments: low (LF) and high (HF) superphosphate application (plus lime on HF), and 3 grazing managements — rotational grazing by sheep (RGS) or cattle (RGC), and set stocking by sheep (SSS). Annual measurements of pasture species abundance (plant unit density and size) were made in each year during 1976–81. Density of plant units was greater in HF than LF (27.8 cf. 25.3 × 103/m2) pastures and, for the 3 different grazing managements, SSS > RGS > RGC (30.1, 25.2, and 17.1 × 103/m2 respectively). In addition, plant density decreased with increasing slope of measurement site, and was influenced by aspect. In most instances, lower plant unit density was compensated for by increases in plant unit size, in accordance with the ‘3/2 thinning law’. This did not occur under RGC because of severe treading damage, and the depression in herbage accumulation rate in these pastures was attributed to this lack of complete compensation. Density of species categories within the total pasture was closely related to botanical composition results presented elsewhere. Moss incidence in pastures was decreased by HF application and RGC management. Several white clover stolon characteristics were measured, of which manipulation of stolon length per unit area of pasture was thought most likely to have effects on white clover productivity.

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