Effect of KCl on bioavailability of manganese

Abstract

Studies were conducted to determine whether KCl application alone or in combination with Mn fertilizer would increase the bioavailability of indigenous and applied Mn and to study the mechanisms by which KCl could enhance Mn uptake by crops. The effect of rates of application (0, 50, 100 and 300 μg K g−1) of two KCl carriers (fertilizer grade and reagent grade KCl), as well as the effects of various salts (KCl, MnSO4, K2SO4, K2CO3, KCl + MnSO4, and KCl + MnSO4 + KI) on Mn uptake by wheat were examined. The effect of KCl on the solubility of soil Mn and applied Mn and the effect of K2SO4 on solubility of soil Mn were examined in calcareous and noncalcareous soils.The two KCl carriers behaved similarly in affecting Mn uptake by wheat. On the calcareous soil only the highest rate of KCl significantly enhanced Mn uptake, whereas on the slightly acidic soil both 100 and 300 μg K g−1 treatments significantly increased Mn uptake. Different salts differed significantly in affecting Mn uptake by wheat, and their effect was observed in the order KCl > K2SO4 > > K2CO3 in both soils, with Mn uptake with K2CO3 being less than in the control. Application of KCl alone, at the higher rates, was as effective as MnSO4 alone in increasing Mn uptake by wheat. Mn uptake by wheat with dual application of MnSO4 and KCl was greater than with separate applications of MnSO4 or KCl. Addition of KCl to MnSO4 fertilizer bands increased amounts of water-soluble Mn in the fertilizer bands. K2SO4 was almost as effective as KCl in increasing water-soluble Mn in MnSO4 fertilizer bands but only for short periods of time (1–3 d). In contrast, KCl increased Mn solubility in the MnSO4 bands for periods up to 56 d. Key words: KCl fertilizer, KCl-enhanced Mn uptake, Mn availability, Mn solubility