Pasture degeneration. I. Effect on total and seasonal pasture production

Abstract

The cessation of superphosphate dressings to a perennial ryegrass-white clover pasture which had received more than 1300 kg superphosphate per hectare resulted in pasture degeneration. Within 2½ years of the last superphosphate dressing, the sown species comprised less than 15% of the harvested forage, compared with 53% in the forage from plots receiving 500 kg superphosphate per hectare per year. Only where superphosphate was applied at either 250 or 500 kg per hectare per year did the ryegrass persist. As perennial ryegrass was the only species to contribute to pasture production in winter, this botanical degeneration significantly reduced winter production. The phosphate-deficient pastures were invaded by summer-growing native grasses such as red grass, which, although contributing substantially to summer production, made little or no growth in the 6 months April to September inclusive.