Abstract
Pasture brome (Bromus valdivianus Phil.) has the potential to increase current levels of herbage production and pasture persistence in New Zealand dryland, well-drained soils. However, there is little literature on the effect of defoliation management on growth of this grass under contrasting soil-water restriction levels. The growth physiology and performance of pasture brome were evaluated in pots in a glasshouse. Defoliation frequency (DF) treatments were applied based on three different accumulated growing degree-days (AGDD): 250, 500 and 1000 AGDD (high, medium, and low DF). At end of the first growing cycle (1000 AGDD), water availability was restricted to 20–25% of field capacity (FC) in half of the pots, while the other pots were maintained between 80–85% FC. Total accumulated herbage mass was positively related with the low DF and well-watered conditions (p < 0.05). At the final harvest, plants subjected to low DF had greater root mass than high and medium DF (p < 0.05). At each harvest, the leaf regrowth stage (LS) for low DF was 3.5, while for high and medium DF, the LS was 1.5 and 2.0; respectively. Tiller water-soluble carbohydrates were highest at the low DF and under 20–25% FC. Regardless of soil-water conditions, defoliation at 3.5 LS supports production, enhancing survival during a drought.
Highlights
Bromes (Bromus spp.) are genus of grass species that include some useful forage types, as well as some weedy species
Unsuitable defoliation frequency leads to depletion of perennial grass species soluble carbohydrate reserves and low root mass resulting in poor survival during drought and slow recover after it [5]
Accumulated herbage mass per pot increased by 32% under low defoliation frequency, with no significant differences between the high and medium defoliation frequencies
Summary
Bromes (Bromus spp.) are genus of grass species that include some useful forage types, as well as some weedy species. Previous research on Bv in New Zealand has shown it produced less total herbage mass than other perennial grasses, such as Dactylis glomerata L. and Festuca arundinacea Schreb., when grown in hill country under dry summer conditions [2]. D. glomerata when sown in a mix with Medicago sativa L. in hill country in the Canterbury region with an average rainfall of 643 mm/year [3] In both of these studies, all the species were defoliated at the same time without considering species-specific defoliation intervals. Unsuitable defoliation frequency leads to depletion of perennial grass species soluble carbohydrate reserves and low root mass resulting in poor survival during drought and slow recover after it [5]
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