PRELIMINARY NITROGEN, PHOSPHORUS, POTASSIUM, CALCIUM AND MAGNESIUM DRIS NORMS AND INDEXES FOR APPLE ORCHARDS IN CANTERBURY, NEW-ZEALAND

Diagnosis and Recommended Integrated System (DRIS) norms and indices for N, P, K, Ca and Mg were developed for apple trees in Canterbury, New Zealand, based on surveys of nutrient levels of apple leaves in field experiments before and after N and K fertiliser applications and in four orchard surveys over a period of three years. Comparisons were made between calculated norms based on mean sufficiency nutrient levels and published norms. Results obtained showed that calculated norms and indices from sufficiency range provide a good indication of the order of apple nutrient requirements. High N and low Ca were identified as major nutrient problems. The best period for sampling leaves for nutrient analysis is at 3 to 5 months after blossom (i.e., December to January in New Zealand).