RESPONSE OF PERMANENT AND RESEEDED GRASSLAND TO FERTILIZER NITROGEN .1. HERBAGE PRODUCTION AND HERBAGE QUALITY

The productivity of permanent swards of mixed species composition was compared with that of sown Lolium perenne, cv. Melle at five fertilizer‐N rates (0, 150, 300, 450 and 900 kg N ha−1) and with L. perenne/Trifolium repens, cv. Grasslands Huia at 0 kg N ha−1. The investigation was conducted under two cutting frequencies at sixteen sites in England and Wales, representing a range of grassland environments. Annual total herbage dry matter (DM) production from both permanent and reseeded swards increased with successive increments of fertilizer‐N up to 450 kg N ha−1. Herbage DM production from reseeded swards in the first year after sowing was signficantly higher than from the permanent swards, at all fertilizer‐N treatments. In subsequent years the production advantage of the L. perenne reseeds was maintained only at the higher N rates, though sown L. perenne/T. repens was the most productive sward type at 0 N. Average differences in modified acid‐detergent fibre suggested small advantages in herbage quality to the reseeded swards. It is concluded that, while reseeded swards are more productive in the year after sowing, many permanent swards are capable of high levels of production and that reseeding to a L. perenne sward cannot always be justified, particularly for grassland receiving low or moderate inputs of fertilizer‐N. Copyright © 1990, Wiley Blackwell. All rights reserved