Nitrogen, Shading Duration, Gas Exchange, and Growth of Cassava

Abstract

The effects of applied N and shading duration on net gas exchange and growth of two southern Florida cassava ( Manihot esculenta Crantz.) cultivars grown in containers were determined. Both cultivars responded similarly to shading and N with respect to the measured variables. There were no interactions between shading duration and N application rate for any of the variables measured. Tissue dry weights, total leaf N and chlorophyll concentrations, net CO 2 assimilation (A), transpiration (E), water-use efficiency (WUE), and stomatal conductance (g s ) were quadratically related to the concentration of N applied to the soil. The optimum N application rate for maximum growth of both cultivars was 60 mg/plant per day. Increased shading duration reduced A, E, g s , WUE, storage root number, and weight and increased the shoot : root ratio.