Evaluation chemical extractants in determination of available potassium for pistachio in calcareous soils of Rafsanjan

Potassium is a very important plant nutrient not only because of its large demand, but also because of its important physiological and biological functions in plant. Therefore, understanding of soil potassium status can lead to better use of potassium fertilizers. This study was done to evaluate 10 extractants for estimating available potassium for pistachio in 28 calcareous soils of Rafsanjan in a completely randomized design with three replications in greenhouse conditions in Vali-e-Asr university of Rafsanjan in 2014. Potassium was extracted by 1 M NH4OAc, 0.01 M CaCl2,2 M NaCl, 0.1 M HNO3, boiling 1 M HNO3, distilled water, 1M NaOAc, Mehlich1, Mehlich3 and DTPA-NH4HcO3.The results showed that extraction of K decreased in the order: boiling 1 M HNO3> 2 M NaCl > 1M NaOAc > Mehlich3> 1 M NH4OAc > 0.1 M HNO3> DTPA-NH4HcO3> Mehlich1> 0.01 M CaCl2> distilled water. 1M NaOAc was selected as the most suitable extractant for potassium in calcareous soils of Rafsanjan on its high correlation with leaf and shoot K concentration. Multiple regression equations indicated that potassium extracted from the soil dependent to different physical and chemical properties of soil such as amount of clay and cation exchange capacity.