Effects of Defoliation on the Longevity of Stand, Dry Matter Yields and Forage Quality of Tall Wheatgrass, Agropyron elongatum (Host) Beauv.1

Abstract

AbstractTall wheatgrass was subjected to three defoliation frequencies at three clipping heights to determine the degree of defoliation the grass would withstand under optimum fertility and supplemental irrigation.At the most intense defoliation treatment (6‐week interval) yield and persistence were directly related to cutting height. At the less intense defoliation treatments (boot stage plus aftermath and flower stage) yield was highest at the 5‐cm stubble height the first 2 years, but by the third year density of the plants had declined to less than 50% of the original. The 5‐cm stubble height was too low for tall wheatgrass at three intensities of use. The 15‐cm cutting height was optimum at low cutting frequencies and the 25‐cm cutting height was optimum at high intensities. Harvesting tall wheatgrass at the boot stage was detrimental to the stand at all three cutting heights.Forage quality, expressed in percentage crude protein, crude fiber, lignin, fat, and ash, was increased under high intensity defoliation. Production of total digestible nutrients (TDN) per hectare was directly proportional to the amount of dry matter produced under the several treatment levels. Frequency of defoliation had more effect on forage quality and production of TDN than did height of defoliation.