Harvest Effects on Switchgrass Persistence.

Perennial grasslands have been converted to crop production, which has decreased available forage resources.  Interest in using switchgrass (Panicum virgatum L.) as a forage is increasing because of its high dry matter (DM) yield and its wide adaption. A 3-yr. study was conducted at Mead, NE from 2004 through 2006 on established ‘Cave-In-Rock’ switchgrass to determine the effect of harvest timing on switchgrass herbage mass and persistence. The experiment was conducted as a randomized complete block design with three replications in a split arrangement of the treatments.  The four whole-plot treatments were month of harvest (Aug. through Nov.) and the five sub-plot treatments were weekly harvests during week of the month (1, 2, 3, 4, or 5). Plots were fertilized with 112 kg N ha^-1 after burning, but before 15 May.  Herbicides were applied as needed for weed control.  Sub-plots were harvested weekly using a flail harvester.  Switchgrass herbage mass peaked during the third week of August and averaged 17,396 kg DM ha^-1 across three years.  Herbage mass declined by about 785 kg DM ha^-1 each month after peak production. These DM reductions were likely from a combination of seed shatter, leaf senescence, and nutrient translocation.  Harvest timing had a small, but inconsistent effect on switchgrass persistence.  Switchgrass herbage mass was influenced by harvest date with the ideal harvest date for maximum switchgrass herbage mass occurring in mid-August.