Herbage yield, tiller number and root system activity after defoliation of prairie grass (Bromus catharticus Vahl)

Abstract

The effects of defoliation upon root and shoot systems of prairie grass (Bromus catharticus Vahl) were examined in both field and pot studies. The varieties used were 78–32 (HY), a high‐yielding variety; 79–42 (LY), a low‐yielding variety; and the commercial variety Grasslands Matua. In the field, the presence of roots in early and late spring was estimated by measuring uptake of [32P]phosphate by roots; herbage yields and tiller numbers were recorded. In a pot study, root and shoot dry‐matter (DM) yields were analysed. In the field, roots were detected to a depth of 1·2 m. After defoliation to a height of 0·1 m, root presence decreased more than 50% at depths of 0·6 m for LY and 1·0 m for Matua in early spring and at several depths for each variety in late spring. After a second defoliation, the apparent growth rate of shoots decreased by 35% in relation to the first regrowth period. In pots, shoot DM and root DM of control plants (undefoliated) had the following allometric relationship of the form: In (shoot DM) = 0·61 + 1·14 ln (root DM) (r2= 0·81). After defoliation, compared with undefoliated controls, the relative growth rate of shoots and total herbage yields were higher, but root and stubble DM were lower in all three varieties. Pooled root DM means were 10·3 and 6·8 g plant−1 and pooled stubble DM means were 12·7 and 7·6 g plant−1 for control and defoliated plants respectively. HY produced heavier tillers than LY, pooled means being 0·94 and 0·53 g DM tiller−1 (field study) and 3·44 and 2·05 g DM tiller−1 (pot study) for HY and LY respectively. HY had 5–6 green leaves per tiller, whereas LY had 3–4. Developed green leaves were heavier in HY (58 g m−2) than in LY (48 g m−2). It is suggested that differences in both leaf parameters may be related to higher herbage yields for HY than LY.

Wildlife Habitat Quality (Sward Structure and Ground Cover) Response of Mixed Native Warm-Season Grasses to Harvesting

“…Sward heights in these previously harvested plots were shorter than their corresponding Y109 plots (control), except for the Y208 at 60-d interval. Shorter sward heights for previously harvested stands were expected due to preferential resource allocation to shoot growth at the expense of roots, as grasses respond to defoliation [32]. Root growth cessation is a plant's response to defoliation that enhances the reestablishment of photosynthetic canopy and root to shoot balance, so bunch grasses can tolerate herbivory [33].…”

Recovery from short-term complete submergence in temperate pasture grasses

“…It is tolerant of shade and mild drought but sensitive to waterlogging (Ploschuk et al 2017). Bromus catharticus (common name prairie grass) is a tufted, short-lived perennial or biennial grass with erect culms (up to 55-84 cm tall), unbranched, and widely distributed in temperate regions of the world (Jatimliansky et al 1997). It is considered sensitive to excess soil water (Ploschuk et al 2017).…”

Seasonal distribution of herbage mass and nutritive value of Prairiegrass (Bromus catharticus Vahl)

“…Defoliation based on leaf appearance rates enables prairiegrass plants to achieve a balance between shoot and root production (Slack et al ., 2000), and nutritive value (Turner et al ., 2006c). Balancing regrowth interval with herbage use sustained available herbage production (Turner et al ., 2006a) and enabled plants to tolerate defoliation and persist in pastures (Jatimliansky et al ., 1997). Careful autumn management, allowing Matua prairiegrass stands the opportunity to reseed in late summer, increased their persistence (Jung et al ., 1994).…”