Comparison of Mehlich-3 and Ammonium Bicarbonate-DTPA for the Extraction of Phosphorus and Potassium in Calcareous Soils from Florida |
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| Authors: | Qiang Zhu Yuncong Li |
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| Institution: | 1. Horticultural Sciences Department, Southwest Florida Research and Education Center, University of Florida, Immokalee, Florida, USA;2. Soil and Water Science Department, Tropical Research and Education Center, University of Florida, Homestead, Florida, USA;3. Soil and Water Science Department, Tropical Research and Education Center, University of Florida, Homestead, Florida, USA |
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| Abstract: | Developing a fast and reliable soil testing method is critical for improving soil testing efficiency and ensuring reliable fertilizer recommendation. The objectives of this study were to evaluate Mehlich-3 (M-3) as a replacement for ammonium bicarbonate-diethylenetriaminepentaacetic acid (AB-DTPA) to extract phosphorus (P) and potassium (K) and to determinate the relationships between extractable P and K and their uptakes by crop in calcareous soils. M-3 and AB-DTPA were compared by using two approaches. In the first approach, the amounts of extracted P and K were compared by analyzing soil samples collected from agricultural production areas; in the second approach, snap beans (Phaseolus vulgaris) were grown in pot to determine the P and K uptakes by crop. There were significant correlations between M-3 and AB-DTPA for both soil test P and K based on soils collected from the agricultural field and the pot study. Soil test P and K by both extractants were significantly correlated with their uptakes by snap bean. The critical value of M-3-P regarding snap bean uptake was 47 mg kg?1 and was higher than that (18 mg kg?1) for AB-DTPA-P, whereas critical soil test K levels were similar between M-3 and AB-DTPA. M-3 was identified as an alternate improved extraction method instead of AB-DTPA in calcareous soils based on this study. However, more work will be needed to identify the correlation of the two extractants and crop responses under a field condition. |
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| Keywords: | Calcareous soil exchangeable potassium extractable phosphorus soil extractant soil test calibration |
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