EFFECT OF KCL ON BIOAVAILABILITY OF MANGANESE

Studies were conducted to determine whether KCI application alone or i n combination with Mn fertilizer would increase the bioavailability of indigenous and applied Mn and to study the mechanisms by which KCI co uld enhance Mn uptake by crops. The effect of rates of application (0, 50, 100 and 300 mug K g-1) of two KCI carriers (fertilizer grade and reagent grade KCl), as well as the effects of various salts (KCl, MnSO 4, K2SO4, K2CO3, KCl + MnSO4, and KCl + MnSO4 + KI) on Mn uptake by wh eat were examined. The effect of KCI on the solubility of soil Mn and applied Mn and the effect of K2SO4 on solubility of soil Mn were exami ned in calcareous and noncalcareous soils. The two KCI carriers behave d similarly in affecting Mn uptake by wheat. On the calcareous soil on ly the highest rate of KCl significantly enhanced Mn uptake, whereas o n the slightly acidic soil both 100 and 300 mug K g-1 treatments signi ficantly increased Mn uptake. Different salts differed significantly i n affecting Mn uptake by wheat, and their effect was observed in the o rder KCI > K2SO4 > > K2CO3 in both soils, with Mn uptake with K2CO3 be ing less than in the control. Application of KCl alone, at the higher rates, was as effective as MnSO4 alone in increasing Mn uptake by whea t. Mn uptake by wheat with dual application of MnSO4 and KCI was great er than with separate applications of MnSO4 or KCI. Addition of KCI to MnSO4 fertilizer bands increased amounts of water-soluble Mn in the f ertilizer bands. K2SO4 was almost as effective as KCI in increasing wa ter-soluble Mn in MnSO4 fertilizer bands but only for short periods of time (1-3 d). In contrast, KCI increased Mn solubility in the MnSO4 b ands for periods up to 56 d.