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This article in AJ

  1. Vol. 92 No. 3, p. 423-427
     
    Received: Jan 19, 1999
    Published: May, 2000


    * Corresponding author(s): glmi@gnv.ifas.ufl.edu
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doi:10.2134/agronj2000.923423x

Using Near Infrared Reflectance Spectroscopy to Schedule Nitrogen Applications on Dwarf-Type Bermudagrasses

  1. Ian R. Rodrigueza and
  2. Grady L. Miller *b
  1. a Horticulture Dep., Clemson Univ., Clemson, SC 29634 USA
    b Environmental Horticulture Dep., Univ. of Florida, Gainesville, FL 32611 USA

Abstract

Due to the high rates of N fertility necessary for producing high-quality turfgrasses, quick, reliable methods of determining the N status of turfgrasses would be valuable management tools. The first objective of this study was to evaluate the use of near infrared reflectance spectroscopy (NIRS) to schedule N fertilization on two dwarf-type bermudagrasses [Cynodon dactylon (L.) Pers. × C. transvaalensis Burtt Davy]. The second objective was to test the accuracy of NIRS-predicted mineral tissue concentrations. The third objective was to study the effect of N fertility on thatch development. `Tifdwarf' and `FloraDwarf' bermudagrasses grown on sand–peat (9:1 by volume) were subjected to five treatments using time, NIRS-predicted N thresholds, and a visual quality rating threshold to schedule applications of (NH4)2SO4 for 20 wk per growing season in 1997 and 1998. There were positive linear relationships between total Kjeldahl nitrogen (TKN) and NIRS-predicted N in 1997 (r2 = 0.76; slope = 0.96) and 1998 (r2 = 0.92; slope = 1.06). NIRS-scheduled fertility resulted in similar quality with less fertilizer than time or visual quality-based fertility. The NIRS mineral concentration predictions for K, Ca, Mg, Fe, Zn, Mn, and Cu were positively correlated with traditional laboratory methods, but there was not sufficient precision in measurements to use NIRS for determination of these nutrients. Thatch development and yields were greater in treatments receiving higher rates of fertilizers, suggesting that excessive growth rates due to high rates of applied fertilizer may have contributed to thatch development.

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