Yield, composition and quality of tall fescue as influenced by N fertility and soil water availability

Abstract

A study was designed to evaluate yield, quality and composition of tall fescue (Festuaa arundinaaea Schreb.) as influenced by water stress under 0, 100, and 400 kg N·ha^‐1 during autumn in the southeastern U.S. Four replicates of each treatment were imposed in a completely random design in the field. The experiment was conducted in two successive years with treatments applied to an adjacent area to eliminate residual or carry‐over effects. Water status was verified by gypsum block, tensiometer, and determination of leaf stomatal resistance. Plant tissue was harvested three times during autumn and again in the following spring. Forage yield total was not significantly affected by soil water stress, apparently due to compensatory growth during recovery periods. Soil water appeared to be more rapidly depleted under 400 kg N·ha^‐1 than other N treatments. Increasing N fertilizer significantly increased leaf area, leaf number, and was inversely related to the number of senesced leaves. Stomatal resistance was increased under water stress conditions when N was limited (ON) but not when 400 kg N·ha^‐1 was applied. Consequently, plots receiving 400 kg N·ha^‐1 continued to transpire even during periods of limited soil water, but transpired less during subsequent stress periods. Kjeldahl and NO₃‐N were increased by application of fertilizer N and only NO₃‐N was significantly increased by water stress in this study. Although high input of fertilizer N minimized the impact of mild water stress on the physiological response of tall fescue, eventual stand loss occurred. Water stress had no effect upon nonstructural carbohydrates, in vitro dry matter digestibility or the elements P, K, Ca, Mg, Cu and Zn. Consequently the factors associated with the expression of tall fescue toxicosis during autumn are more subtle in expression, and do not appear to be associated with alterations in major nutritive components.

Notes

Contributions of the USDA‐ARS Southern Piedmont Conservation Research Center, Watkinsville, GA 30677 and Russell Research Center, Athens, GA 30613.

Research Agronomist, Soil Scientist, SPCRC, Watkinsville, GA and Research Microbiologist, RRC, Athens, GA.