CLASSIFYING SOILS OF THE SOUTH AFRICAN SUGAR INDUSTRY ON THE BASIS OF THEIR NITROGEN MINERALIZING CAPACITIES AND ORGANIC MATTER CONTENTS

form maus. The merits of organic matter (OM) content of the Results of field and laboratory studies have indicated that the N requirement of ratoon cane can be more reliably estimated from a knowledge of the soil form and/or the organic matter status of the soil. Soils may be classifies according to their N mineralizing capacity (high, medium or low) and an incubation study indicated that the release of mineralizable nitrogen correlated well with the organic matter contents of the soils. Soils of low, medium and high mineralizing capacities were found to correspond broadly with soils containing 4% organic matter respectively. This was substantiated by yield responses from field trials conducted on a range of soils where indications were that the probability of a response to applied N increased as the organic matter content of soils declined.