Response of herbage regrowth and water‐soluble carbohydrate concentration of ryegrass species to defoliation practices when grown in a Mediterranean environment

Abstract

Three experiments were conducted to determine the association between leaf number per tiller at defoliation, water-soluble carbohydrate (WSC) concentration and herbage mass of juvenile ryegrass plants when grown in a Mediterranean environment. Seedlings of ryegrass were grown in nursery pots arranged side-byside and located outside in the open-air to simulate a mini-sward in Experiments 1 and 2, and a mixture of annual ryegrass and subterranean clover (Trifolium subterraneum L.) was grown in a small plot field study in Experiment 3. Swards were defoliated mechanically with the onset of defoliation commencing within 28 d of germination. Frequency of defoliation ranged from one to nine leaves per tiller, whilst defoliation height ranged from 30 mm of pseudostem height that removed all leaf laminae in Experiment 1, to 50 mm of pseudostem height with some leaf laminae remaining postdefoliation in Experiments 2 and 3.A positive relationship between herbage mass of ryegrass, WSC concentration and leaf number per tiller at defoliation was demonstrated in all experiments. In Experiment 1, the herbage mass of leaf, pseudostem and roots of tillers defoliated at one leaf per tiller was reduced to 0AE10, 0AE09 and 0AE06 of those tillers defoliated less frequently at six leaves per tiller. However, the reduction in herbage mass from frequent defoliation was less severe in Experiment 2 and coincided with a 0AE20 reduction in WSC concentration of pseudostem compared with 0AE80 measured during Experiment 1. In Experiment 3, the highest harvested herbage mass of ryegrass occurred when defoliation was nine leaves per tiller. Although the harvested herbage from this sward contained senescent herbage, the in vitro dry-matter digestibility of the harvested herbage did not differ significantly compared with the remaining treatments that had been defoliated more frequently.Leaf numbers of newly germinated ryegrass tillers in a Mediterranean environment were positively associated with WSC concentration of pseudostem and herbage mass. A minimum period of two to three leaf appearances was required to restore WSC concentrations to levels measured prior to defoliation thereby avoiding a significant reduction in herbage mass. However, maximum herbage mass of a mixed sward containing ryegrass and subterranean clover was achieved when defoliation was delayed to nine leaves per tiller.

Changes in water‐soluble carbohydrates relative to crude protein in perennial ryegrass in response to defoliation frequency

“…These results are consistent with those observed by Hume (1991) and Callow et al (2005) who found that frequent defoliation reduced herbage mass and leaf size in various grass species. These results are consistent with those observed by Hume (1991) and Callow et al (2005) who found that frequent defoliation reduced herbage mass and leaf size in various grass species.…”

Harvest management based on leaf stage of a tetraploid vs. a diploid cultivar of annual ryegrass

“…() using perennial ryegrass ( Lolium ryegrass L.), Callow et al. () annual ryegrass ( Lolium rigidum Gaud.) and Italian ryegrass ( Lolium multiflorum Lam.…”

“…Defoliation treatments were imposed when greater than 50% of 10 randomly selected tillers attained the set number of fully expanded leaves, that is, 2, 3 and 4 leaves/tiller (Callow, Michell, Baker, Cocks, & Hough, ; Fulkerson & Slack, ; Turner, Donaghy, Lane, & Rawnsley, ). The expansion of each new leaf was termed “1‐leaf stage” and thus the respective treatments were referred to as 2‐leaf, 3‐leaf and 4‐leaf stages.…”

Effects of cutting frequency on plant production, N‐uptake and N2 fixation in above‐ and below‐ground plant biomass of perennial ryegrass–white clover swards

“…(1997), who also used a leaf‐labelling technique. Similar to the present study, Callow et al. (2005) found in pot and small plot experiments that the root biomass of perennial ryegrass constituted a considerable proportion of the total plant biomass with shoot:root ratios estimated to be in the range of 0·8–1·2.…”