The ability of three plant species to take up potassium from phlogopite

Potassium (K) is an essential element for plant growth and development and its importance in agriculture is well known. It plays an important role in improving the quality of agricultural products. Besides, micaceous minerals are abundant in Iranian soils. The role of plant species in potassium uptake from minerals is significant; but not well investigated. Therefore, the objective of this research was to compare the ability of various plant species (alfalfa, barley and tall fescue) to utilize non-exchangeable and structural potassium from phlogopite. Barley, alfalfa and tall fescue are known as second major crop in Iran, the most important forage crop worldwide and natural forage grass, respectively. The experiment was laid out in a completely randomized design with factorial combinations and all treatments were triplicate. Experimental factors were three plant types (barley, alfalfa and tall fescue), 2 culture medium (phlogopite + quartz sand, and quartz sand) and two nutrient solutions (K-free and complete). Culture media was a mixture of quartz sand (as filling material) and phlogopite. Pots were irrigated with distilled water and nutrient solutions during a period of 140 days. At the end of experiment, shoots and roots were separated and plant samples were prepared with dry ashing method and the concentration of K was determined with flame photometer. The K concentration was in sufficient limit for both barley and alfalfa in pots amended with phlogopite under K-free solution. But K concentration was not in sufficient limit for tall fescue under K-free condition. Among plants tested, K uptake followed the order: barley > alfalfa > tall fescue (P<0.05). In pots amended with phlogopite under K-free nutrient solution, K remove by barley, alfalfa and tall fescue was calculated as 50, 41 and 28; respectively. The net potassium release was greatly influenced by plant species. Plant demands for K and root morphology are important factors for these differences among plants. Although, micaceous minerals are abundant in Iranian soils, these sources can be removed by plants under intensive cropping; therefore under these conditions potassium fertilization is recommended.