Abstract
A field experiment was conducted to determine the recommended application rate of nitrogen fertilizer for mixed sown meadow of perennial ryegrass (Lolium perenne L.) and white clover (Trifolium repens L.) in Tenpoku Region in 2002-2004. The meadow was cut three times per year, and nitrogen fertilizer was applied at four levels : 0, 60, 90 and 120kgN/ha/year. The increase in DM yield per unit nitrogen applied was greatest at the 90kg application rate. However, nitrogen fertilizer reduced the proportion of legumes in the pasture, especially at the third cut in the 120kg treatment when the proportion was less than 10% in every year. At the second cut especially, higher rates of nitrogen fertilizer increased in vitro dry matter digestibility and water soluble carbohydrate contents, and decreased fiber content. We conclude that the recommended rate of nitrogen fertilizer is 90kgN/ha per year. At this rate, we estimate that the clover supplies about 40kgN/ha per year for grass growth.
