SOME EFFECTS OF FERTILIZATION ON THE YIELD, BOTANICAL AND CHEMICAL COMPOSITION OF IRRIGATED GRASS AND GRASS-CLOVER PASTURE SWARDS

In an irrigated pasture experiment on Vancouver Island, on a soil deficient in available nitrogen and potassium but apparently containing sufficient available phosphorus, calcium and magnesium for adequate plant growth, an irrigated Ladino clover-grass mixture greatly outproduced a grass mixture on a forage, protein and mineral nutrient yield basis. In order to attain even a moderate yield with a grass mixture, heavy fertilization with nitrogen and potassium was necessary. Nitrogen fertilization was not essential to high yields with the Ladino clover-grass mixture. Nitrogen fertilization tended to decrease the per cent Ladino clover and the protein and calcium content in the clover-grass forage and increased the protein content of the grass herbage. The calcium content of the grass herbage was decreased by nitrogen fertilization. The phosphorus and magnesium contents of the clover-grass and grass herbage were not appreciably altered by nitrogen fertilization. Decreasing the time interval between nitrogen applications resulted in a more even production of dry matter over the growing season but did not increase the total seasonal yield. Potassium fertilization increased the yield of both mixtures and increased the per cent clover in the grass-clover sward. Multi-annual potassium applications were required for the elimination of plant potassium deficiency symptoms and the applied potassium was quickly absorbed by the plants. Grass herbage contained more potassium, slightly more phosphorus and less calcium, magnesium and nitrogen than grass-clover herbage.