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This article in CS

  1. Vol. 51 No. 4, p. 1727-1738
     
    Received: Sept 11, 2010
    Published: July, 2011


    * Corresponding author(s): aldermap@ufl.edu
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doi:10.2135/cropsci2010.09.0516

Carbohydrate and Nitrogen Reserves Relative to Regrowth Dynamics of ‘Tifton 85’ Bermudagrass as Affected by Nitrogen Fertilization

  1. P. D. Alderman *a,
  2. K. J. Bootea,
  3. L. E. Sollenbergera and
  4. S. W. Colemanb
  1. a Dep. of Agron., Univ. of Florida, PO Box 110500, Gainesville, FL 32611-0500
    b USDA ARS, Subtropical Agricultural Research Station, 22271 Chinsegut Hill Road, Brooksville, FL 34601-4672. This research was supported in part by the USDA, Tropical Subtropical Agricultural Research Program

Abstract

Carbohydrate and N reserves are important for perennial grass regrowth after defoliation. The objective of this study was to quantify the effects of N fertilization on dynamics of reserve accumulation and utilization for regrowth of a C4 perennial grass. A field study was conducted at Gainesville, FL, on established ‘Tifton 85’ bermudagrass (Cynodon spp.) in 2006 and 2007. Treatments were N rates of 0, 45, 90, and 135 kg N ha−1 regrowth period−1. Total nonstructural carbohydrate (TNC) and N concentrations, leaf area index (LAI), and canopy carbon exchange rate (CER) were measured weekly during 28-d regrowth periods. Stem and rhizome TNC concentrations decreased with increasing N rate, ranging from 20 to 80 mg g−1 for stem and 45 to 145 mg g−1 for rhizome, and followed quadratic time trends, with minima between 7 and 14 d of regrowth, suggesting reserve utilization up to 2 wk after defoliation. Leaf, stem, rhizome, and root N concentrations increased with N rate. Leaf and stem N concentrations followed quadratic time trends, with maxima between 7 and 14 d of regrowth, and ranged from 15 to 50 mg g−1 for leaf and 10 to 40 mg g−1 for stem. Rhizome N concentrations were constant throughout regrowth. Canopy CER and LAI followed logistic time trends within each 28-d regrowth period, with upper asymptotes raised by increased N rate. Nitrogen fertilization increased TNC reserve utilization, LAI, and canopy CER, thereby increasing shoot regrowth at rates up to 90 kg N ha−1 period−1.

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