The regrowth of Aberystwyth S. 23 perennial ryegrass, S. 24 perennial ryegrass, S. 59 red fescue and S. 170 tall fescue was studied in field swards, comparing four levels of applied nitrogen, for 8 weeks following a clearing cut. The clearing cuts were in midOctober, mid-February and mid-March in each of 3 years, different plots being used on each occasion.The application of N increased the number of leaf primordia, the number of unemerged leaves, the rate of leaf emergence and death, leaf blade length, width and weight, sheath length, number of leaves per unit area of ground and proportion of green tissue in total yield. The application of N had little effect on the number of leaves per tiller and tended to reduce weight per unit area of leaf blade. The increase in size, weight and number of leaf blades appeared to be major reasons for the positive effect of applied N on yield, previously reported; and the increase in sheath length contributed to the increase in proportion of yield above 4 cm. Rate of leaf extension was not closely related to yield and was more sensitive to temperature than was yield. Changes during regrowth in blade and sheath length helped to explain changes in weight per tiller, previously reported. The effects of improving weather conditions in late winter/early spring were similar to the effects of applied N: larger, heavier leaf blades, longer sheaths, a taller canopy, a lower proportion of dead material, younger leaves. The length of shoot apex per leaf primordium was relatively constant. Leaves continued to emerge, at a slow rate, in the period December-February. S. 170 had the biggest leaves, particularly in May, and the slowest rate of leaf turnover. Rate of leaf extension was increased by applied N more, on average, in the ryegrasses than in the fescues.indirectly, with grassland management to develop a fuller understanding of reasons for yield differIn an earlier paper (Wiknan, 1980) a field experi-ences so that management decisions can be more ment concerned with early spring and late autumn soundly based, response to applied nitrogen in four grasses was described and the results for yield, number of tillers EXPERIMENTAL PROCEDURE and chemical composition presented and discussed. In the same experiment leaf initiation, rates of leafThe experimental treatments, field procedures emergence and extension, leaf blade area and weight, and weather have been described previously sheath length and proportion of green tissue in total (Wilman, 1980). Regrowth after a cut in field swards yield were studied in order to gain a more com-of grass sown as pure stands was studied for 8 weeks plete view of the effects of applied N, grass species at three times of year in each of 3 years, using and variety, stage of regrowth, time of year and different plots on each occasion. All combinations weather. The two papers together present a much of four levels of applied N and four grasses were more comprehensive set of data on this topic, for compared. A randomized-block design was used, early spring and la...