The Availability of Magnesium from Organic Carriers in Artificial Substrates.

Abstract

Several organic carriers of Mg in comparison to magnesium sulfate were tested for their suitability for alleviation of apple leaf scorch. Corn and apple seedlings were grown in water and sand cultures in which each of these several compounds in turn were a part of a complete nutrient solution. Chief results were as follows: 1. Apple seedlings grew much better in sand culture than in water culture and the results on the former are more reliable. 2. The buffering effect of the organic carriers kept the pH of the nutrient solutions at higher levels than those containing magnesium sulfate. When all were maintained at the same lower level by adjustment of the NO3/NH4 ratio, adverse growth effects were produced with most of the organic compounds tested. 3. When the pH of those solutions containing organic carriers was allowed to remain higher, there was markedly better growth with many of them than with the magnesium sulfate controls. Of the compounds tested two were toxic: magnesium thiocyanate and salicylate. Fourteen gave no benefit: lignin sulphonate, glycerophosphate, versene, nitrate-urea, anthranilate, pyruvate, benzoate, adipate, sebecate, gluconate, levulinate, methyl-, ethyl-, and butyl-phosphate. Seven were distinctly more beneficial to both corn and apple growth than sulfate. These were acetate, formate, phthalate, ammonium phosphate, malate, lactate and fumarate. Propyl phosphate was beneficial for apple but not for corn.