Utilization of fluidized bed material as a calcium and sulfur source for apples

Abstract

Fluidized bed material (FBM), a dry, high Ca, alkaline waste product which results from combining coal and limestone, was used as a Ca or S source or lime substitute in an established apple orchard (Malus domestica Borkh., cv. ‘York Imperial') over a four year period. Treatment comparisons were made between FBM applied at one or two times (1x or 2x) the soil lime requirement and CaCO, applied at the lime requirement (lx). Additionally, FBM lx was compared to a combination treatment consisting of CaCO₃ plus gypsum to apply similar amounts of Ca and S. All treatments were also compared to an untreated control.

No significant treatment comparisons were noted on leaf Ca levels however leaf Mg significantly decreased when FBM applied at the 1x or 2x level compared to CaCO₃ 1x. When FBM was compared with CaCO. plus gypsum there was a significant decrease in leaf Ca with FBM but no difference in leaf Mg. These effects were probably due to either a solubility difference between nutrients or to actual amount of Mg applied by the different sources. Leaf S levels were unaffected by treatments. Yields, fresh fruit weight and the incidence of cork spot were little affected by treatments.

Soil extractable Mg, 1N NH₄Ac, was not a good prediction of leaf Mg content or Mg added to the soil. Only soil Al was significantly reduced, compared to the control, by the treatments among the metals studied (Zn, Mn, Cu, Cd, Pb and Al). FBM applied at twice the lime requirement (wt. basis) resulted in similar soil pH to CaCO₃ applied at the lime requirement.