Abstract
This study was conducted to investigated potassium release kinetics in Zawitta (Duhok) province in northern Iraq. Soils were classified within Mollisol order under different forest tree types (Walnut, Betoum, Common Pine, Oaks, Almond, Occidental, Out of forest (Control)). Potassium release was conducted by successive extraction by using (0.01 M) oxalic acid. The results show the potassium release capacity were decreased with increaseing time of abstraction. The different of potassium in chemical and physical properties of soil were effected clearly with in the capacity release rate of potassium and path way of reaction also the results show that path way reaction according to parapulic diffusion consist of two stage (first one represent exchangeable phase with high rate and the second represent non exchangeable potassium release with slow rate). Potassium release (capacity and release) in first stage was more than the second stage. Soils under forest trees gave a different capacities for potassiumrelease as following orders (Walnut, Oaks, Occidental, Almond, Betoum, Common Pine, Out of Forest (Control). The high value for exchangeable capacity was in sub soil horizon for (Walnut) (66.32 mg.kg-1), while the lower value were in sub surface of (Pine forest) (0.87 mg.lg-1). The highs value for non-exchangeable potassium were in sub horizon surface under (Walnut Forest) (423.2 ml g.kg. minute 0.5), while the lower value were recorded in sub surface horizon in (Pine Forest) (45.37 ml g.kg. minute 0.5). Rate of potassium release from exchangeable phase recorded a high value in sub surface horizon (Walnut Forest) (27.78 ml g.kg. minute 0.5), while the lower value were recorded in sub surface horizon for Pine forest (4.17ml g.kg. minute 0.5). Potassium non exchangeable were recorded high value in sub surface horizon for (Walnut Forest) (4.67 ml g.kg. minute 0.5), while the lower value were recorded in sub surface horizon from control (1.26 ml g.kg. minute 0.5). In generally all horizons in pedons were characterize with homogenus. Surface horizon were high in each of potassium release capacity and potassium rate and decreased with depth. according to soil fertility evaluation and depending on potassium capacity release and rate from Mica minerals which show the low reserve (47-490) and low rate release. All of these soils regard as low supplying for potassium there for, these results may be have important to treaded potassium problems under forest soil.
