USING RAPID ANALYTICAL METHODS TO QUANTIFY NUTRIENTS IN SUGARCANE LEAF TISSUE

NIR spectroscopic methods are frequently used to measure the nutrient composition of leaf tissue in crops such as citrus fruits, forage crops, vegetables and forestry. However, sugarcane applications are more limited. This paper presents an investigation into the use of NIR spectroscopic methods for the measurement of nutrient elements in prepared sugarcane samples under laboratory conditions. The nutrient elements measured were: carbon, nitrogen, phosphorus, potassium, calcium, magnesium, sulphur, copper, iron, zinc and manganese. Calibrations capable of quantitative measurements were developed for carbon (R2 0.87, SEP 0.22), nitrogen (R2 0.98, SEP 0.06) and calcium (R2 0.85, SEP 0.07), while calibrations capable of screening applications were obtained for potassium (R2 0.89, SEP 0.10), magnesium (R2 0.82, SEP 0.03), sulphur (R2 0.89, SEP 0.03) and potentially phosphorus (R2 0.66, SEP 0.05). No calibrations were successfully developed for the trace elements. These results provide a solid foundation for the development and application of NIR spectroscopic methods to measure nutrient element concentrations in sugarcane leaf tissue samples in a laboratory situation. Further work will be required to develop the technology to a field-ready capacity. This will involve spectral collection using a lower resolution portable NIR instrument to measure ‘raw’ samples in the field followed by traditional sampling and wet-chemical analysis. Subsequent calibration development will focus on optimising the calibrations for the low-functionality, portable instrument prior to appropriate field trials to demonstrate utility.