Phosphorus in Morgan Soil Test Extracts Measured By Molybdate Colorimetric and Inductively Coupled Plasma Spectroscopy Methods |
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| Authors: | Eric O Young Donald S Ross Bruce R Hoskins |
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| Institution: | 1. Research Department, William H. Miner Agricultural Research Institute, Chazy, NY, USA;2. Department of Plant and Soil Science, Jeffords Hall, University of Vermont, Burlington, VT, USA;3. Analytical Laboratory and Maine Soil Testing Service, School of Food and Agriculture, Orono, Maine, USA |
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| Abstract: | Colorimetric P determination mainly reflects inorganic P, whereas inductively coupled plasma spectroscopy (ICP) measures all P in solution. We compared Morgan extractable P for ICP (MP-ICP) and colorimetry (MP-Color) using dairy farm field samples (0 to 20 cm) across northern New York (n = 250) and hayfield transect samples (0–15, 15–30, 45–50 cm; n = 164). Soil organic matter, pH, and extractable cations were also measured. Mean ratio of MP-ICP: MP-Color was 1.46 and differed significantly among Morgan P categories, ranging from 1.89 for low to 1.06 for very high. The numeric difference between MP-ICP and MP-Color ranged from 0 to 12.9 mg kg?1. Organic matter, Al, and pH jointly accounted for 55% of the variability between methods across samples. Fertilizer P recommendations differed based on the two methods, suggesting results from both methods should be reported, particularly in the responsive range. |
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| Keywords: | Inductively coupled plasma Morgan soil test phosphorus |
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