Defoliation Management Effects on Productivity, Nutritive Value, and Persistence of 'performer' Switchgrass.

‘Performer’ switchgrass (Panicum virgatum L.) was released in 2006 by the USDA-NCSU forage program because of its greater digestibility compared to standard cultivars grown in the Southeastern U.S. Forages with greater digestibility have potential to positively impact animal responses and information on defoliation regimes is critical to ensure its persistence and productivity. The objectives of this study were to determine the effect of the factorial combination (4 x 4) of defoliation stubble height (SH, clipped to 10, 20, 30, and 40-cm) and defoliation frequency (DF, clipped every 3, 6, 9, and 12 wk) on herbage mass, crude protein (CP), digestibility (IVTD) on ‘Performer’ switchgrass and weed infestation. The experiment was conducted at the Central Crops Research Station, Clayton, NC. There was no SH effect on herbage mass for 3- and 6-wk DF (4.4 and 6.4 Mg ha^-1, respectively); nevertheless, herbage production increased from ~6.8 to ~12.1 Mg ha^-1 for both 9- and 12-wk DF when SH was lowered from 40 to 10 cm. The IVTD ranged from 723 to 755 g kg^-1 due to SH, being lowest and greatest for 10- and 40-cm SH, respectively; however, the IVTD range was greater due to DF, being lowest for 12-wk DF at 584 g kg^-1 and greatest for 3-wk DF at 882 g kg^-1. The CP ranged from 83 to 99 g kg^-1 for 9- and 12-wk DF and from 120 to 161 g kg^-1 for 3- and 6-wk DF. Weed infestation was mainly due to crabgrass (Digitaria spp.) and it was greater (~70% infestation) when defoliation occurred every 3-wk at 10-cm SH and remained below 15% for all other treatments. Frequent defoliation strategies such us every 3 wk to 20-cm SH or 10-cm SH for DF ≥ 6 wk are viable to ensure productive and persistent forage stands of ‘Performer’ switchgrass.