Sugarcane Leaf Nutrient Concentrations: With or Without Midrib Tissue

Abstract

The literature on sugarcane (interspecific hybrids of Saccharum spp.) leaf-nutrient composition usually reports values either with (W) or without (WO) the midrib tissue, but not for both. The removal of the midrib adds an extra step to the sampling process. The effects of sampling time (May and October) and method (W and WO midrib) on leaf-blade nutrient concentration of cultivar CP 78-1628 were investigated on a Margate sand (siliceous, hyperthermic Mollic Psammaquents) in a split-plot randomized complete block design. The presence of the midrib resulted in decreased concentrations of nitrogen (N) phosphorus (P), calcium (Ca), magnesium (Mg), zinc (Zn), manganese (Mn), and iron (Fe) in the leaf sample to varying degrees, but increased concentration of potassium (K). Simple correlation coefficients between samples analyzed W and WO the midrib were ≥0.75 for P, Ca, Mg, and Mn in May. The percent-errors of predicting WO midrib values from W midrib values were greater than 20 when tested with published data. Although differences between W and WO midrib were verified for sugarcane leaf-nutrient compositions, at this time it is not possible to predict WO nutrient concentration from W data. When reporting sugarcane leaf-nutrient values, therefore, a statement on the sampling method with regard to the midrib must be included. Estimated differences between sugarcane leaf-nutrient concentrations W and WO midrib values were ≥10.0, ≥1.0, and ≤1.2 g kg− 1 for N, P, and K, respectively, when W midrib leaf-nutrient concentrations were lower than the published critical W midrib value. This result shows that it will be important for sugarcane growers and researchers to use the appropriate critical value (WO or W midrib) for N and P, but not for K.