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)

Abstract

A small-plot experiment was made to assess the influence on dry-matter output from grass of a wide range of fertilizer nitrogen and defoliation interval treatments. There were five defoliation treatments, 22, 28, 45, 75 and 112-day regrowth intervals throughout the growing season each at six levels of nitrogen application, ranging by 300 kg increments from 0 to 1500 kg/ha/year.There was a marked interaction effect between treatments; a positive dry-matter response was maintained to a higher level of applied nitrogen with more frequent defoliation. In 2 years out of 3 maximum dry-matter yield was produced under a 75-day defoliation interval although the mean yield advantage over a 45-day defoliation system was only 11 %. Mean yield of digestible dry matter appeared to reach a maximum under a 45-day defoliation interval at 600 kg N/ha but at the lower levels of N the maximum yield was reached at the longest growth interval.Seasonal response to nitrogen under the 22-and 28-day defoliation systems measured as the increase in yield resulting from increased N at each cutting date reached its peak in July-August. Application for these short growth periods early and late in the growing season appeared to be a relatively inefficient use of nitrogen.The less frequently the sward was harvested and the higher the nitrogen application the greater was the reduction in ground cover as estimated by eye at the end of the growing season, this reached an estimated 25% reduction under 112-day defoliation at 300 kg N/ha/year.In relation to published figures nitrate content of herbage did not reach dangerous levels until nitrogen application reached levels beyond those at which maximum dry-matter yield was achieved.

An assessment of the influence on net herbage accumulation, herbage consumption and individual animal performance of two lengths of grazing rotation and three herbage allowances for grazing beef cattle

“…Cutting experiments have shown that a significant proportion of the difference between long and short defoliation intervals may arise from differences in yield at first defoliation (Bartholomew & Chestnutt, 1977). The difference in defoliation interval in the present experiment was nominally 15 days but, since grazing on both interval treatments started on the same day, mean difference in time of initial defoliation over the first cycle of each rotation length treatment was only 6 days.…”

“…The extent to which these manipulations may have affected production is difficult to assess although, since variation in herbage allowance throughout the experiment had little influence on NHA, the effect of grazing pressure manipulation on grass yield is likely to be small. It is estimated that under a cutting regime the difference in initial defoliation date would reduce the difference in total yield over the season at the two defoliation intervals from 30 to 24% (Bartholomew & Chestnutt, 1977;Binnie, Chestnutt & Murdoch (1980). It was perhaps rather surprising to find that herbage allowance treatments produced no significant effect on NHA, since increasing degree of defoliation is considered to reduce D.M.…”

The influence of nitrogen and defoliation on production and water‐use efficiency ofLolium multiflorumcv. Midmar

“…Maximum DM production in a study on perennial ryegrass was obtained with a 10.5-week cutting interval (Bartholomew & Chestnutt 1977), which was only 11% more than the production obtained with a 6.5-week interval. In another study, Wilman (1975) obtained maximum DM production with Italian ryegrass after an 11 »week regrowth period.…”

“…Increased N fertilisation results in an increase in dry matter (DM) production, but this increase levels off above a certain critical N application level. For ryegrass this critical level is reached with approximately 400 to 500 kg N ha 4 a" 1 (Cowling & Lockyer 1970;Bartholomew & Chestnutt 1977;Smith 1977;Pimentai et at. 1978;Hart & Widdowson 1981;Ehlig & Hagemann 1982;Eckard 1989).…”

Comparative productivity of irrigated short-term ryegrass (Lolium multiflorum) pasture receiving nitrogen, grown alone or in a mixture with white (Trifolium repens) and Persian (T. resupinatum) clovers

“…In other environments, yield of these pastures has been related to total N applied, rather than to an application rate per defoliation. The recommended rate is generally about 300-500 kg N/ha.year (Bartholomew and Chestnutt 1977;Morrison 1980;Eckard 1989); this is equivalent to the local recommendations of 5-8 applications at 60 kg N/ha.application.…”