Evaluating garlic available potassium with chemical extractants

The extractions of soil potassium (K) by chemical methods were compared as predictors of plant-available K for pot-grown garlic (Allium sativum) on 10 Hamadan-Iran soils. The treatments include 2 K levels (0 and 200 mg/kg as K2SO4) and 10 soils in a factorial experiment in a randomized block design with three replications. The result indicated that K application increased yield, K concentration and K uptake by garlic. Relationships between methods were discussed. The 13 extracting solutions used in this study were classified in 4 groups on the basis of K extracted. The correlation studies showed that NH4OAc, AB-DTPA, and boiling 1 M HNO3 could not be used as available K extractants. But the correlation of other extractants with relative yield, plant response, and additional K uptake were significant. Potassium critical levels by different extracting solution were determined by Cate-Nelson method. Soil potassium critical levels by 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 for 90% relative yield were 131, 50, 46, 184, 163, 203, 202, 41, 50, and 31 mg/kg, respectively.