Mineral Leaf Composition of Sweet Sorghum in Relation to Biomass and Sugar Yields under Different Nitrogen and Salinity Conditions

Abstract

Diagnosing nutrient insufficiencies or toxicities in sorghum through foliar analysis is still unusual and mainly used for grain sorghum. The influences of the combinations of four nitrogen (N) rates with three sodium chloride (NaCl) rates on the leaf N, phosphorus (P), calcium (Ca), magnesium (Mg), potassium (K), and sodium (Na) concentrations of sweet sorghum [Sorghum bicolor (L.) Moench ssp. saccharatum], cropped for ethanol production, and on biomass and sugar yields were evaluated in three consecutive years of an experiment established on a Eutric Fluvisol equipped with a trickle irrigation system (“triple emitter source”). The relationships among leaf nutrient concentrations, dry matter, and sugar yields were also examined. Nitrogen, much more than salinity, affected leaf nutrient concentration, stem dry weight, and sugar yield. Leaf N concentration was the best indicator for predicting sugar production of sweet sorghum.

Keywords:

• Leaf analysis
• nitrogen
• salinity
• sugar yield
• sweet sorghum

Acknowledgements

This work was funded by the Fundação para a Ciência e a Tecnologia (FCT), under the framework of the Project “Optimization of Nitrogen Fertilization According to the Salt Content of Irrigation Water” (2007–2010).