Management of Switchgrass‐Dominated Conservation Reserve Program Lands for Biomass Production in South Dakota

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Abstract
Switchgrass (Panicum virgatum L.) has been planted on land enrolled in the Conservation Reserve Program (CRP). Management strategies for conversion of this land from CRP to biomass energy require evaluation. Objectives of this study were to: (i) determine the effect of harvest timing and N rate on biomass production and characteristics of switchgrass land enrolled in or managed similarly to CRP and (ii) evaluate the impact of harvest management on species composition and persistence. Five N rates (spring applications of 0, 56, 112, and 224 kg ha−1 and 224 kg ha−1 split between spring and postharvest) and two harvest timings (anthesis and post‐killing frost) were applied to plots from 2001 to 2003 at three South Dakota locations. Harvesting after a killing frost produced higher total yields and improved switchgrass persistence compared with anthesis harvests. The concentration of neutral detergent fiber (NDF), acid detergent fiber (ADF), and acid detergent lignin (ADL) increased between anthesis and killing‐frost harvests, while total nitrogen (TN) and ash decreased. Nitrogen applied at 56 kg ha−1 increased total biomass without affecting switchgrass persistence, but there was no additional benefit with N above 56 kg ha−1 Harvesting long‐established switchgrass stands once per year after a killing frost and applying N at 56 kg ha−1 was an effective system for switchgrass biomass production and persistence on land enrolled in or managed similarly to CRP in South Dakota.