Compensatory Growth of Tall Fescue Following Drought1

Abstract

AbstractEnhancement of growth following short periods of drought stress has been reported in several crop species. If such enhancement follows summer drought‐stress of cool‐season forage grasses, the increased yield from summer irrigation may be offset partially by compensatory growth during fall. Therefore, a 3 year field study was conducted to compare growth responses of tall fescue (Festuca arundinacea Schreb.) grown with and without supplemental irrigation from June through August. Soil was Mexico silt loam (Udollic Ochraqualf) and fertilizer was applied in spring and following each cutting. Plots were harvested six times in 1971, five times in 1972, and four times in 1973. A residual harvest was made on 21 May 1974.During summer the plants that were irrigated had greater forage yields, greater tiller density, greater weight per tiller, higher leaf elongation rates, and higher concentration of water‐soluble carbohydrates (WSC) in leaf tissue as compared with plants that were water‐stressed. Concentration of WSC in stem bases during summer was higher in the water‐stressed plants. Fall growth of plants that had been water‐stressed during summer was greater than that of those that had been irrigated. The enhancement of growth or compensatory effect was associated with higher concentration of WSC in stem bases during late summer, and faster leaf elongation and greater weight per tiller during fall of the previously water‐stressed plants as compared with the summer‐irrigated plants.Compensatory growth following drought stress was still evident the following spring, as indicated by the higher tiller density and greater forage yield. However, the collective compensatory yield of the water‐stressed plants during fall and spring was not great enough to compensate for lower yields during summer. In the third year of the study normal rainfall during summer was higher than duing the first 2 years, and no compensatory growth was noted during fall or the following spring.During the 3‐year study, total yield for the irrigated treatments was 4% larger than that for the water‐stressed treatment. The major response to irrigation was a shift in season of production. Management and breeding objectives should consider the effect of summer irrigation or summer drought on the subsequent performance of cool‐season forage grasses.