Yield and canopy characteristics of switchgrass ( Panicum virgatum L.) as influenced by cutting management

Perennial warm season grasses, such as switchgrass ( Panicum virgatum L.), complement cool-season species by filling the period of low biomass production called summer-slump. Although switchgrass is widespread in the Great Plains of the USA, there is very little information available about its management in mountain regions. A field experiment was conducted in Blacksburg, VA, USA, to determine the influence of dates of first and regrowth harvest, and cutting height on the canopy structure of the winter hardy cv. ‘Pathfinder’. The number, height and weight of tillers, yield distribution, light penetration through the canopy, leafiness, specific leaf area and leaf area index were investigated. Harvested biomass yield increased as date of first harvest was delayed throughout June and cutting height was reduced from 300 mm to 200 mm, but the yield of regrowth declined accordingly. This decline was caused by the removal of an increasing percentage of apical meristems and increasing damage to the crop canopy, in particular the loss of a greater proportion of photosynthetically active leaf area. A lower cutting height also reduced the amount of biomass produced in the following year. Cutting at 300 mm in early June can maximise the amount of high quality (defined as high concentrations of in vitro digestible dry matter and crude protein) biomass available for use as animal feed as compensation for cool season grasses during the first half of July.