Pasture degeneration. II.* The importance of superphosphate, nitrogen and grazing management

Abstract

Fertilizer application and grazing management were shown to be important factors affecting trends in botanical composition in a 5-year-old perennial ryegrass–white clover pasture showing signs of pasture degeneration. In the absence of continuing superphosphate application, native and weed species invaded the pasture, irrespective of grazing management. However, where superphosphate was applied at 500 kg ha-1 year-1, the subsequent trends in botanical composition were dependent on the grazing strategy used. Pastures which were intensively grazed during the winter-spring period were invaded by red grass and other native grass species following a decline in the perennial ryegrass component, whatever the grazing management of other times of the year. In contrast, lax grazing, or pasture spelling, during this winter-spring period led to an increase in the basal area of ryegrass and checked the encroachment of unsown species. The role of superphosphate and grazing management in maintaining stable and productive pastures on the Northern Tablelands of New South Wales is discussed. Part I, Aust. J. Agric. Res., 29: 9 (1978).