Productivity, Persistence and Response to Nitrogen of Italian Ryegrass Varieties

The production of six varieties of Italian ryegrass was compared for three years by cutting 5 or 6 times during the growing season. All varieties showed falls in production of dry matter at high and low levels of N fertilization, but New Zealand HI and New Zealand Italian ryegrass showed significantly lower falls and gave top yields over the three years, in spite of severe frost damage in the first two. Crude protein and nitrogen absorption remained high at the lower level of fertilization (174–209 lb N/acre) and showed a fall only in the third year at the high level of N fertilization (348–418 lb N/acre). The significance of the high response of the New Zealand varieties is discussed.