Nitrogen and Harvest Management for Switchgrass Quantity and Quality.

Switchgrass (panicum virgatum) is widely acknowledged as a realistic raw material for bioenergy production on marginal lands. Growing switchgrass for bioenergy production will distinctively alter management strategies from those of the past, specifically for nitrogen fertilizer inputs and harvest timing. Managing switchgrass for quality components (e.g. ash content), as opposed to strictly for yield, is important for growers because energy producers will not accept plant material that may risk clogging up boilers. To address these management concerns on switchgrass quality, a two year field project was conducted in southwest Wisconsin. The objectives of this study were to: (1) determine optimal N fertilizer rates and harvest timings to maximize switchgrass production, (2) evaluate the effects of N fertilizer rate and harvest timing on switchgass moisture, ash, alkali metal and chlorine content and (3) develop management recommendations for switchgrass producers and energy producers. Four N rates (0, 56, 112, 168 and 224 kg ha^-1) and three harvest timings (early October, late November and mid-April) were evaluated. Results indicate there is a trade-off between switchgrass quantity and quality.