THE EFFECTS OF VARIOUS INCREMENTS OF N, P AND K ON THE YIELD AND BOTANICAL COMPOSITION OF PERMANENT PASTURES

Abstract

Applications of N, P and K to an area grazed and unfertilized for over 30 years resulted in some immediate and marked improvements in yields and botanical composition. Phosphorus, at rates up to 80 pounds per acre, brought about the most marked improvement. This element was responsible for highly significant increases in yield, increased wild white clover and useful grasses and decreased weeds, moss and bare ground markedly. Potassium, up to 60 pounds per acre, also gave highly significant increases in yield. Potassium had relatively little effect on the prevalence of species at first, but by the fourth year had maintained white clover better than phosphorus and had also decreased weeds and moss. Nitrogen, at 15 pounds per acre, increased yields each year but only during the early part of the season. Thirty pounds per acre was superior to the 15-pound rate one year only and this was also during the early part of the season. It actually tended to decrease yields during July and August. The effect of nitrogen on botanical composition was largely to decrease the percentage of wild white clover with a corresponding increase in grasses.