Efficient use of fertilizer nitrogen on grass swards: effects of timing, cutting management and secondary grasses

Abstract

Efficient use of nitrogen (N) is necessary for cost effective grass production and to minimise risks of water pollution. A guide to spring N application, the Dutch T sum 200°, has been compared with two accumulated soil temperature systems. When used in conjunction with soil and weather conditions, all the systems are of practical value. The temperature targets require adjustment for altitude, and allow a degree of flexibility in timing of N application. Potential herbage yield and quality from a series of silage cutting systems were assessed. By manipulating the date of first cut, level of N, regrowth interval and number of cuts, it was possible to devise multi-cutting systems which would attain specified yield and quality targets for various livestock systems. Certain grasses common in permanent grassland e.g. Holcus, Festuca and Agrostis species, can outyield Lolium perenne at N levels up to 120 kg N ha⁻¹ yr⁻¹ but not above. However, the digestibility of L. perenne is superior to the other species. Several secondary grasses had high N concentrations because they did not metabolize high N uptakes into high dry matter yields. In certain situations, better management of the existing species may be preferable to reseeding.