Effect of a spring application of nitrogen on the performance of perennial ryegrass-white clover swards at two sites in the Netherlands

Abstract

In a field trial in 1989-93 on clay soil at Lelystad, Netherlands, a mixed sward of Lolium perenne cv. Profit and Magella and Trifolium repens cv. Retor was given annual applications of 0, 25, 50, 75 or 100 kg N ha-1 and was cut 4-5 or 6-7 times a year. In a trial in 1992-94 on sandy soil in Overijssel, a sward of L. perenne cv. Meltra, Citadel and Condesa oversown with T. repens cv. Retor in 1991 was given annual applications of 0, 50 or 100 kg N ha-1. Average annual dry matter (DM) yields were 14.66 and 13.76 t ha-1 year-1 for the clay and sandy soil, respectively. Yields increased with increasing N rate at both sites. Cutting frequency had no consistent effect on DM yield, and there was no significant interaction between N rate and cutting frequency. T. repens contents decreased with increasing N rate, reducing the DM yield in the cuts after the first in the fertilized treatments. Annual N yields were not affected by N application. The higher cutting frequency increased the T. repens content from 36 to 47% and the N yield from 458 to 524 kg ha-1, but did not affect the DM yield.