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Title: NUTRIENT FILM TECHNIQUE TO EVALUATE CLIPPING HEIGHT EFFECTS ON ORCHARDGRASS SHOOT BIOMASS PRODUCTION AND ROOT DYNAMICS

Author
item Ritchey, Kenneth
item Zobel, Richard
item Snuffer, Josie

Submitted to: American Forage and Grassland Council Conference Proceedings
Publication Type: Proceedings
Publication Acceptance Date: 6/10/2004
Publication Date: 6/24/2004
Citation: Ritchey, K.D., Zobel, R.W., Snuffer, J.D. 2004. Nutrient film technique to evaluate clipping height effects on orchardgrass shoot biomass production and root dynamics. The 2004 Conference of the American Forage and Grasslands Council Conference Proceedings, June 12-16, 2004, Roanoke VA. Vol 13, pp 424-428.

Interpretive Summary: Effects of clipping height and frequency on roots are little studied, partly because plants are usually destroyed in the process of accurately measuring root length and diameter. In order to see whether Nutrient Film Technique (NFT) procedures could be adapted to allow better evaluation, we conducted an NFT experiment to compare responses of orchardgrass clipped at three heights with responses reported in the literature. Clipping to 1" every 2 weeks apparently reduced leaf area available for photosynthetic capture of light energy so much that forage yield, plant size, and root weight were inferior. Clipping to 4" resulted in the greatest biomass accumulation and root size, as was expected, so we concluded that growth in the NFT system was consistent with that predicted in the literature. We constructed an advanced NFT system with a transparent base that allows detailed study of dynamic response to clipping through non-destructive measurement of root length and diameter every 15 minutes. We found that clipping did not cause root death but did stop root elongation for about 2 days. Knowing effects of clipping on root dynamics should help in knowing when to apply fertilizer to rotationally grazed pastures.

Technical Abstract: Some cultivars and species have been reported to respond to grazing by decreasing total root length and rooting depth. One mechanism proposed is that defoliation causes extensive root death followed by renewed root growth in shallower layers of the soil. Dynamic effects of clipping height and frequency on roots are little studied, partly because plants are usually destroyed in the process of accurately measuring root length and diameter. In order to see whether Nutrient Film Technique (NFT) procedures could be adapted to allow better evaluation, we conducted an experiment to compare responses of orchardgrass to biweekly clipping at three heights under NFT conditions with responses reported in the literature. Clipping to 1" every 2 weeks markedly reduced forage yield, plant size, and root weight. Clipping to 4" resulted in the greatest biomass accumulation and root size, as was expected. We concluded that growth in the NFT system was consistent with expected behavior based on published data. We constructed an advanced NFT system with a transparent base that allowed detailed study of dynamic response to clipping through non-destructive measurement of root length and diameter every 15 minutes. We found that clipping did not cause root death but did stop root elongation for about 2 days. Understanding effects of clipping on root dynamics should help us know when to apply fertilizer to rotationally grazed pastures.