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Response of Four Tall Fescue Cultivars Grown at Two Nitrogen Levels to Low Soil Water Availability¹

Four cultivars of tall fescue (Festuca arundinacea, Schreb.) ‘Ky-31 (GA)’, ‘Fawn’, ‘Kenhy’, ‘G1-306’ were grown in controlled environments to evaluate the interactive effect of N and soil water availability on biomass production, leaf water potential (_L), as well as Kjeldahl N, NO₃-N and the amino acid proline. Two N fertility regimes [0 kg N/ha (O N) and 200 kg N/ha (200 N)], and two successive drought stress and recovery cycles were imposed in controlled environment chambers with a third and final stress period imposed in the greenhouse. Drought stress reduced biomass production in all cultivars. Application of 200 N improved dry matter production of all cultivars under drought stress except G1-306. Leaf roll was apparent in most cases of drought stress. Leaf water potential responses were not consistent over successive drought stress cycles; that is, preconditioning minimized the change in _L, indicating that some adjustment to stress conditions were being made by the plant. Nitrogenous components including Kjeldahl N, NO₃-N and proline were distinctly affected by drought stress. Kjeldahl N was significantly increased by drought stress in all cultivars but especially in Kenhy and G1-306 at the 200 N level. Proline concentrations were increased by drought stress in all cultivars, with Fawn containing the highest and G1-306 the lowest concentration of proline. Since there is a specific response of nitrogenous components to drought stress these responses may represent fundamental alterations in N metabolism and may not be similar for all cultivars. Our findings indicate the need for further analysis of the distribution and composition of the nitrogenous fractions of drought-stressed tall fescue.

Key Words: Drought stress • Leaf water potential • Proline

² Research agronomist, supervisory soil scientist, and plant physiologist, respectively, USDA-ARS, Southern Piedmont Conserv. Res. Ctr., Watkinsville, GA 30677.

Received for publication February 19, 1981.