Potassium forms in soil and its separates in some loess and loess-like soils of Golestan providence

Potassium is essential plant macronutrients. According to the conceptual approach soil potassium (K) can be classified into four forms: soil solution K, exchangeable K, fixed K and structural K. In this research, potassium forms were determined in loess and loess like derived soils of Golestan Province and in the silt and clay fractions of them. The objective of this research was to determine the contribution of soil separates in release of potassium and to be fertilizer management in the soils. Mean extracted potassium content in clay particles of all soils was more than that of soil and silt fraction. The quantity of K extracted by HNO3, NH4oAc and HF in soils varied from 632 to 1200, 103 to 476 and 12000 to 17800 mg/Kg, respectively. The mean of exchangeable, nonexchancheable and total potassium contents were 160.6, 1155.1 and 19100 mgKg-1, respectively in clay fraction. The quantity of non exchancheable K extracted from silt fraction was a half of its quantity in clay fraction.