The effect of interval between harvests and nitrogen application on the numbers and weights of tillers and leaves in four ryegrass varieties

Abstract

The effect of six intervals between harvests and three levels of N application on the number of tillers was studied in four ryegrass (Loliutn) varieties in the first harvest year and in two varieties in the second and part of the third harvest years in a field experiment. Weight/tiller was recorded in the first 2 years and weight/green leaf and number of green leaves harvested were recorded in the first year.There was a large negative interaction between level of N and interval between harvests in respect of number of tillers, the number being increased by N with short intervals and tending to be reduced by N with long intervals. The interaction was larger in the second and third years than in the first. The negative interaction in respect of number of tillers and number of green leaves harvested was associated with a reduction in the percentage increase in yields of dry matter, digestible organic matter and N due to the application of N as the interval was increased. It is suggested that one should in general avoid a combination of high N and long intervals between harvests with present varieties of perennial ryegrass.The effects of interval between harvests, N application, variety and time of year on number of tillers and weight/tiller are discussed in relation to their effects on yield to show how tiller information can contribute to a better understanding of the ways in which yields are achieved. Rather low yields in the late summer and early autumn of the second harvest year were in many instances attributable to a rather low number of tillers rather than to low weight/tiller.There was a considerable increase in number of tillers between the end of one growing season and the early part of the next, suggesting that the period in which this increase is achieved may be an important one in relation to the continued vigour of the sown species.A reduction in annual yield of green leaf with extension of interval from 6 to 10 weeks with N applied resulted from a reduction in the number of green leaves harvested/ harvest and in the number of harvests, which outweighed an increase in number of green leaves harvested/tiller and in weight/green leaf. Increasing the level of N with intervals of 3-6 weeks increased the number of tillers, the number of green leaves harvested per tiller and per unit area of ground and weight/green leaf and hence consistently increased green leaf yield.

The effect of a wide range of fertilizer nitrogen application rates and defoliation intervals on the dry-matter production, seasonal response to nitrogen, persistence and aspects of chemical composition of perennial ryegrass (Lolium perennecv. S.24)

“…yield is likely to be obtained with defoliation intervals longer than 45 days. Considering nitrogen treatments no greater than 600 kg N/ha/year the mean effect of increasing defoliation interval was similar to that observed by Wilman, Koocheki & Lwoga (1976), yields of digestible D.M at 22, 28 and 45 days representing 67, 76 and 95 % respectively of the yield under a 75-day cutting system. Reith & Inkson (1961) and Heddle (1967) have observed that the response of grass to applied nitrogen may be limited without adequate potash application.…”

Some environmental effects on relationships betweenin saccodegradability of protein and dry matter and chemical composition of Italian ryegrass

“…Carbohydrates soluble in water represent a considerable soluble part of DM. Findings of some other studies (Wilman and Wright, 1978;Wilman et al, 1976) also confirmed that the content of easily soluble carbohydrates decreases as the intensity of N fertilizing increases.…”

The response of Italian ryegrass to nitrogenous fertilizer at different times of year, with particular reference to residual effects

“…Longer sheaths would increase the proportion of the total number of tillers in the sward which were present and identifiable as tillers in the harvested produce (Wilman, 1977) and would partly account for the very large effect of N on number of harvested tillers in the year in which these were recorded. The counts in the sward in the other 2 years, however, showed a moderately large effect of N on the number of tillers in the sward, which would be expected in the circumstances of these experiments (Wilman et al 1976c). From the limited number of counts in the present experiments it appeared that a positive residual effect of N on dry-matter yield may be associated more with a positive residual effect on size, and particularly D .…”