Nutrient status of sugar cane in relation to leaf nutrient concentration

Abstract

The nitrogen, phosphorus, and potassium requirements of sugar cane were studied in relation to the concentration of these elements in the leaf tissue of three varieties of sugar cane grown commercially in Fiji. Percentage yields of sugar cane in fertilizer field experiments were highly correlated with leaf nutrient levels in the control plots, provided leaf sampling was carried out during the maximum growth period of mid- January to mid-May. For each nutrient there was a marginal zone of leaf concentration below which crops always gave significant yield responses to applied nutrients and above which crops failed to respond. Marginal zones for crops sampled during mid-March to mid-May were 1.4-2.0 per cent for nitrogen, 0.13-0.21 per cent for phosphorus, and 0.9-1.5 per cent oven dry leaf for potassium. Within the deficient range of leaf nutrient concentrations there was little relationship between optimum rates of fertilizer required to correct the deficiency and leaf nutrient levels of unfertilized cane. Because of the lateness of sampling, any indication of fertilizer requirement would only be applicable to a subsequent ratoon crop.