| Abstract: | Regrowth characteristics of a cocksfoot (Dactylis glomerata L.) sward after initial defoliation at different stages of development Over 2 two-year period (1984-1985) the productivity of Dactylis glomerata (cv. Baraula) swards as influenced by variations in time of the initial defoliation was studied. The stages at which the initial cuts were taken were: (a) before stem apices were raised to defoliation level (5 cm), (b) about two weeks later, when the reproductive tillers reached ear emergence, (c) about 4 weeks after (a), when the reproductive tillers reached flowering stages. Subsequent production was measured by weekly harvesting of representative sward samples over a 6-7 weeks lastening growth period. Furtheron patterns of growth in a second regrowth in August and a third regrowth in September/October were studied. The growth behaviour in the investigation was described by calculations of curves concerning mainly the development of dry matter yield (DM), leaf area index (LAI), crop growth rate (C), relative growth rate (R) and net assimilation rate (E) during the growth period. The leaf area ratio (F) and leaf weight ratio (LWR) were derived from fitted curves. The highest dry matter yield and the highest growth rate (more than 20 g m?2day?1) was estimated in the spring growth and in the earliest regrowth (a). About 30 % of the tillers in these swards became reproductive. The main difference between regrowths of primary defoliations at successively later dates was between the earliest, after cutting on 8.-13. May, on the one hand, and, on the other hand, the two later regrowths after primary cuts from 31. May to 12. June. The two latter and the second regrowth in August were in most respects very similar: no reproductive development; herbage yield of about 400-500 g m?2; highest C of about 15-20 g m?2day?1; maximum LAI- values from 8-9. In respect to the E there were some differences between the stands. The E was at the time when C was highest somewhat higher in the reproduction stands (spring growth and first regrowth) compared with the vegetative regrowths. The relationship between C and LAI could in all stands be described by an relatively optimum curve, which means that C did not differ much within a wide range of LAI. |
