Evaluation of Chemical Extractants Ability for Extracting Available Potassium in Some Tobacco-cultivated Soils in Northwest of Iran

Potassium (K) plays a vital role in increasing the tobacco yield and controlling important quality parameters such as leaf combustibility. In order to evaluate chemical extractants ability to extract available soil K, a greenhouse experiment was conducted in a complete randomized block design with 26 soil samples with 3 replicates in some tobacco-cultivated soils in northwest of Iran. Evaluated K extractants were 1M NH4OAc, 1M NaOAc, 1M NaCl, 0.1 BaCl2, 0.1M HNO3, 0.01 HNO3, 0.01M CaCl2, NaTPB (5min.), NaTPB (4hs), H2O, NH4HCO3-DTPA, Mehlich I, Mehlich III and Morgan- Wolf methods. There was positive and significant correlation among potassium extracted by all the extracting methods. Leaf yield and potassium concentration in tobacco leaves were highly correlated with potassium extracted with 1M NH4OAC (r= 0.88, r= 0.94, respectively), NaTPB 4h (r=85, r=0.91, respectively), and 0.1 M HNO3 (r= 0.87, r=0.93, respectively). In soils with Kave /clay ratio less than 9, correlation coefficients between tobacco quantitative components and Kext significantly decreased. It was conluded that 1M NH4OAC and 0.1M HNO3 is suitable as soil testing methods for determining available K for tobacco in the soils of tobacco fields in northwest of Iran. These extractants showed high correlation with leaf potassium concentration and tobacco leaf yield. In addition, these two methods are simple procedure and cost effective.