Evaluation of the Capability of Extractants in Determining Garlic Available K for Certain Soils in Hamadan

Garlic (Allium Sativum) is a major crop in Hamadan Province. However, adequete information on K status in this region is not available and no suitable extracting solution can yet be introduced. This experiment was carried out to determine the available K level in 10 soils from Hamadan region. The treatments included two K levels (0 and 200 mg K /kg soil as K2SO4) and 10 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 garlic. On the basis of K extracted, the extractants were classified in 4 groups, and the correlation between extractants in each group was significantly high. The correlation studies showed that NH4OAC, AB-DTPA and boiling 1 M HNO3 can not be used as an available K extractant. The correlation of other extractants with relative yield, plant response and additional uptake were significant. Therefore, these extracting solutions can be used as available K extractant. Potassium critical levels by extractants were also determined using Cate-Nelson method. Potassium critical levels for 90 percent relative yield were 131, 50, 46, 184, 163,203, 202, 41, 50 and 31 mg kg-1 for Mehlich 1, 0.002 M SrCl2, 0.01 M CaCl2, 0.1 M BaCl2, SrCl2 + Citric acid, Sodium acetate, 0.1 M HCl, 0.05 M HCl, 0.025 M H2SO4 and distilled water, respectively.