Evaluation of Chemical Extractants for the Determination of Available Potassium
2008
Hosseinpur, A.R. | Samavati, M.
Evaluation of nutrient status in soil is important for nutritional, environmental, and economical aspects. This research was carried out to determine the potassium (K) available to corn (Zea mays) in 15 soils from the Hamedan province in the west of Iran. The treatments included two K levels [0 and 200 mg K kg-1 as potassium sulfate (K₂So₄)] and 15 soils in a factorial experiment in a randomized block design with three replications. The results indicated that K application increased yield, K concentration, and K uptake of corn. According to the mechanism of the extraction, these extractants can be classified into four groups. The first group of extractants, acidic extractants, includes 0.02 M strontium chloride (SrCl₂)+0.05 M citric acid, 0.1 M hydrochloric acid (HCl), and Mehlich 1. The second group includes 0.1 M barium chloride (BaCl₂), 0.01 M calcium chloride (CaCl₂), and 1 M sodium acetate (NaOAc). The third group includes 1 M ammonium acetate (NH₄OAc), ammonium bicarbonate-diethylenetriamine tetraacetic acid (AB-DTPA), and finally distilled water. The results showed that correlation between extractants in each groups were significantly high. Correlation studies showed that NH₄OAc and AB-DTPA cannot be used as available K extractants. The correlation of other extractants with relative yield, plant response, and K uptake were significantly high. Therefore, these extracting solutions can be used as available K extractants. Potassium critical levels by extractants were also determined using the method by Cate and Nelson (1971). Potassium critical levels for 90% relative yield were 29, 27, 82, 84, 45, 145, and 272 mg kg-1 for 0.002 M SrCl₂, distilled water, 0.02 M SrCl₂+0.05 M citric acid, 0.1 M HCl, Mehlich 1, 1 M NaOAC, and 0.1 M BaCl₂, respectively.
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