Seasonality of production limits when warm-season grass biomass can be provided to the bio-refinery. Delaying harvest after occurrence of a freeze extends this period, but the utility of this practice depends on its effect on biomass yield and composition. The objective was to quantify the effect of delaying harvest after first freeze on biomass dry matter (DM) harvested and composition of two perennial grasses. During a 3-yr experiment, elephantgrass (Pennisetum purpureum Schum.) and energycane (Saccharum spp. hybrid) were harvested shortly before or immediately after first freeze plus an additional two to three times during the subsequent 50 to 60 d in northern Florida. Extending the harvest period did not affect energycane biomass yield (avg. 27.6 Mg DM ha -1 ) during 2 yr, but elephantgrass yield decreased on average from 30.7 to 21.5 Mg DM ha -1 as harvest was delayed. Elephantgrass biomass DM concentration was greater than energycane (377 vs. 356 g kg -1 , respectively, in Year 1; 515 vs. 370 g kg -1 , respectively, in Year 2). Concentrations of cell wall constituents in both grasses increased as harvest was delayed after freezing, and the increase was generally greater for elephantgrass than for energycane. Delaying harvest of energycane after a freeze is effective in increasing the period when biomass can be supplied to the bio-refinery, but elephantgrass is less well suited for this management approach because biomass harvested declines with time after a freeze event.
Blackberry (Rubus fruticosas L.) can be a weed in rhizoma peanut (Arachis glabrata Benth.)–grass pastures. Goats (Capra hircus) have provided effective control of Rubus spp. in other environments, but their efficacy has not been tested in legume‐grass swards in this context. The objective was to evaluate rotational stocking by goats alone or with cattle (Bos spp.) for blackberry control. Treatments stocked at 2.6 animal units (AU) ha−1 included a cattle‐alone control, goats alone, concurrent stocking of cattle and goats, sequential stocking of cattle followed by goats, and sequential stocking of goats followed by cattle. The final treatment was concurrent stocking at a stocking rate of 3.5 AU ha−1. Goats grazed blackberry readily, but cattle avoided it. Blackberry selection was greatest when goats followed cattle sequentially. The blackberry proportion of total biomass increased 10% when cattle grazed alone but was reduced 11% with goats alone and 13% with mixed concurrent grazing at a high stocking rate. Treatments including goats resulted in reductions or smaller increases in blackberry mass than for cattle alone. Goats alone or with cattle resulted in greater removal of blackberry leaf and in reduced height and stem density than cattle alone. Goats reduced the blackberry contribution more than cattle, but it was not eliminated from initially heavily infested pastures across 2 yr of grazing. A greater goat stocking rate or a combination of grazing and mowing may be needed for complete eradication.
Sand blackberry (Rubus cuneifolius Pursh) is a troublesome perennial weed in Florida rhizoma peanut (Arachis glabrata Benth.)–grass pastures. The degree to which it can be controlled by defoliation is not well understood. In 2011 and 2012, blackberry regrowth and persistence responses were assessed by clipping every 35 d to three stubble heights (8, 16, and 24 cm), with or without simultaneous removal of all leaf from remaining stubble. Blackberry dry matter harvested decreased linearly (12.8 to 8.5 g m−2) as clipping stubble height increased when remaining stubble leaf was removed, but there was a linear increase in blackberry harvested with increasing clipping stubble height (12.1 to 26.0 g m−2) if remaining stubble leaf was not removed. Across stubble heights, cumulative change in blackberry cover across the 2 yr was −15% units if stubble leaf was removed compared with +1% unit when leaf remained intact. As stubble height increased from 8 to 24 cm, blackberry cover increased linearly, both when stubble leaf was removed (−18 to 0% units, respectively) and when leaf remained intact (−12 to +17% units, respectively). In Year 1, blackberry stem density decreased 10 stems m−2 when stubble leaf was removed and 4 stems m−2 when leaf remained intact, but there was no effect of leaf removal in Year 2. Both clipping stubble height and removal of leaf mass affected blackberry regrowth and cover responses, suggesting that combining leaf removal by browsing animals with periodic close mowing will reduce blackberry cover, mass, and stem density.
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