Carbohydrate Reserves and Tillering of Switchgrass Following Clipping

Abstract

AbstractStands of switchgrass (Panicum virgatum L.) often decline following defoliation, a response often attributed to a high fertile/vegetative stem ratio and a paucity of basal shoots and foliage. Information is lacking on interactions among meristem removal, tiller development, and energy reserves. Field studies on a Mexico silt loam soil (Udollic Ochraqualf) were conducted for 2 yr to examine tillering and total nonstructural carbohydrate (TNC) trends of ‘Pathfinder’ switchgrass following clipping. Harvests were taken on six dates between the vegetative and heading stage during two consecutive years. In Year 2, tiller density was determined periodically during the season. First‐harvest yield increased 699 kg ha−1, and regrowth yield decreased 281 kg ha−1 with each week delay of first harvest. When apical meristems were removed, TNC in aboveground tissue declined more (28 vs. 5 g kg−1) during regrowth and to a lower concentration (51 vs. 43 g kg−1) than when apical meristems remained intact. By the end of the growing season, all clipped plants had similar TNC concentrations, but uncut plants contained 22 and 40% more TNC in above‐ and belowground tissue, respectively, than clipped plants. Tiller development appeared to be unrelated to TNC or to date of first harvest when harvested between vegetative and heading stages. However, clipping during the first year reduced yield during the second year by 34 to 60%. Lengthy regrowth periods following severe defoliation, defoliation that allows apical meristems or leaf area, or both, to remain, and control of weeds are likely to enhance stand maintenance and plant vigor of switchgrass.