Nitrogen fertilization of north coastal grassland—yield, per cent protein, total uptake

The primary benefit of nitrogen fertilization to grassland areas of north coastal California was the increase in production of forage during the winter season when grass was short and legumes grew very slowly. According to these tests, not more than 80 pounds N per acre should be applied since near maximum forage yields were produced at this rate and little increase in winter production resulted from additional amounts. However, carryover into the second year was measurable only with applications of the 160-pound maximum used in these tests on two soil types. Protein percentages in the nonleguminous plants increased with increasing N application rates during the vegetative stage, but at maturity, the nitrogen percentages in these plants were less where 40 pounds of N per acre had been applied than on the non-treated check plots. The 160-pound rate increased the protein percentage in mature plants. Total nitrogen uptake of all forage species combined, increased during the winter with increasing rates of N applied. However, uptake on the unfertilized plots during the warm spring months, when the clovers grew rapidly, was about the same as that on plots fertilized with 40 pounds of nitrogen per acre.