Stockpiled Prairiegrass‐Brassica Hybrid Mixtures Tolerate Repeated Defoliation in Autumn

Abstract

Stockpiling herbage helps redistribute nutrient availability and supplements quantity to sustain or finish livestock, depending on production objectives. In the Appalachian region of the USA, autumn stockpiled herbage is harvested, with little expectation for useable regrowth. Brassica spp. and prairiegrass (Bromus catharticus Vahl.) grow vigorously in autumn and tolerate defoliation providing a means to extend productivity in autumn. Mixed stands of prairiegrass and a brassica hybrid were established in late June of 2003 and 2004, with clipping begun in mid‐September to determine production and nutritive value of regrowth herbage. Stockpiled prairiegrass‐brassica hybrid stands tolerated repeated clipping, but stockpiled yield and the number of regrowth harvests decreased with increased duration of the stockpile interval, and no regrowth harvests were obtained when the stands were stockpiled until mid‐November (130 days after planting). Regrowth accounted for as much as 35% of total yield in autumn when stockpiled harvests were made prior to late October (about 115 days after planting). Nutritive value expressed in terms of nonstructural carbohydrates, crude protein, and total digestible nutrients varied depending on year, but decreased with successive clippings or increased stockpiling duration. Herbage and nutrient yield of a prairiegrass‐brassica hybrid mixed stand declined substantially after mid‐October, in part, reflecting a shift in growth from leaf to tuber in the brassica component of the stand. Stockpiling stands of prairiegrass‐brassica hybrid beyond mid‐October essentially eliminates any meaningful regrowth production. Regrowth from stands clipped prior to mid‐October extends the duration of growth of the mixture and makes a modest contribution to total herbage production in autumn.