Kaliumernährung des Tabaks auf einem K‐fixierenden nordwestiranischen Boden

Abstract

Potassium nutrition of tobacco on a potassium fixing alluvial soilA field experiment was conducted to study the effects of K‐fertilization on potassium uptake by tobacco and the K‐dynamics in an alluvial soil rich in clay and carbonate content. It was observed that the amount of exchangeable potassium and the concentration of K in the soil solution increased on fertilization. There were only small changes in exchangeable potassium and significant reduction in the concentration of K in the soil solution during the growth period.Uptake of potassium by plants increased during first month due to its high concentration in soil solution. Decrease in the concentration of potassium after one month caused a rapid reduction in the uptake of potassium by plants (Figure 1).K Fertilization decreases the K‐Ca and K‐Mg potentials especially during the first month (Table 2) which increase again during the experimental period (because of the slow release of K from the solid phase and its rapid uptake by plants). Where as the concentration of potassium in the soil solution is closely related with K‐Ca and K‐Mg potentials on the one hand and with K‐uptake by plants on the other, no relationship was observed between exchangeable potassium content and K‐uptake (Figure 2).The potassium exchange curves of soils from K0 and K5 treatments show that the extent of K‐adsorption is greater in K0 soil. A major part of K adsorbed during the shaking experiment can be easily removed by CaCl2 solution in K5soil, where as in K0 soil a part of adsorbed potassium exists in nonexchangeable form. Illite is the dominant clay mineral in this soil which show wedge type structures (expansible at edges).