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Using Near Infrared Reflectance Spectroscopy to Evaluate Phosphorus, Potassium, Calcium, and Magnesium Concentrations in Bermudagrass

Application of nutrients to correct nutrient deficiencies in turfgrasses are often based on tissue analysis. Previous research has indicated that near infrared reflectance spectroscopy (NIRS) may be useful in tissue nutrient concentration determination since it requires minimum sample preparation and has been a reliable predictor of N concen- tration. The objective of this study was to evaluate the reliability of NIRS in determin- ing P, K, Ca, and Mg concentrations in bermudagrass (Cynodon dactylon (L.) Pers. x C. transvaalensis Burtt Davy). Tissue samples were collected from Florida golf courses, representing different cultivars grown under various conditions and fertilizer regimes. Tissue samples were analyzed using NIRS and traditional wet chemistry (Mehlich-1 ex- tracts analyzed using inductively coupled argon spectrophotometer) before results were statistically compared. Results from wet chemistry analysis averaged 15% lower than those obtained from NIRS. Although results for certain cultivars and elements were positively correlated ('Tifdwarf∑ Ca, r2 = 0.72; P < 0.01), precision across all cultivars and nutrients was not sufficient (accounted for only 26% of variability) to indicate that NIRS would be an effective management tool for the elements evaluated in this study.