|JACKSON, RANDALL - University Of Wisconsin|
Submitted to: Communications in Biometry and Crop Science (CBCS)
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/6/2013
Publication Date: 10/28/2014
Citation: Brink, G.E., Casler, M.D., Jackson, R.D. 2014. Response of four temperate grasses to defoliation height and interval. Communications in Biometry and Crop Science. 9(1), 15–25.
Interpretive Summary: Cool-season grass productivity and longevity are influenced by the frequency and intensity of leaf removal, either by mechanical means or by grazing. The manner in which frequency and intensity of leaf removal is managed on a grazing-based dairy will have a large impact on pasture productivity, milk productivity of grazing cows, and the cost of purchasing feed that would otherwise be provided by the pasture. Our study determined how different cool-season grasses respond to a range of leaf removal treatments that simulate grazing. We found that the leaf growth, root growth, and production of new grass plants increases as the cutting height and cutting interval increases. The negative effect of short grazing interval and height on root growth, however, has greater adverse implications for long-term productivity and persistence of cool-season grasses than the reduction in leaf growth and new plants produced. The results emphasize the importance of appropriate grazing management to the long-term health of cool-season grass pastures.
Technical Abstract: Herbage removal by grazing or mechanical means impacts productivity and persistence of temperate grasses. Our objective was to determine how extent and frequency of defoliation influences growth and development of diverse temperate grasses under controlled conditions. Field-grown tillers of meadow fescue [Schedonorus pratensis (Huds.) P. Beauv.], orchardgrass (Dactylis glomerata L.), reed canarygrass (Phalaris arundinacea L.), and quackgrass [Elymus repens (L.) Gould] were transplanted into the greenhouse, and after reaching 25 cm height, clipped to a 5- or 10-cm stubble height. Tillers were subsequently clipped to the same stubble height every 7, 14, 21, 28, or 35 d for two growth cycles. Tiller growth was destructively measured 7, 14, 21, and 28 d after the last defoliation. Grasses produced approximately 70% more herbage dry wt. and 50% more root dry wt. when defoliated at a 10- compared with a 5-cm height. Herbage and root dry wt. exhibited linear and quadratic increases, respectively, in response to defoliation interval, but regrowth rate increased from 19 mg herbage dry matter (DM) d-1 and 7 mg root DM d-1 at a 7-d interval to 47 mg herbage DM d-1 and 20 mg root DM d-1 at a 35-d interval. Changes in root:shoot ratio during regrowth were relatively small in grasses subject to a 10- compared with a 5-cm defoliation height. Under the resource-limiting conditions of field environments, the effect of short defoliation height and interval on root growth would likely have a greater detrimental effect on temperate grass productivity and persistence than reduced herbage growth.