Simulation of production potential of self-defoliating sugarcane cultivars

Abstract

Cane burning before harvest is increasingly questioned due to environmental concerns. Harvesting of un-burned or green cane, whether by mechanical or manual means, increases trash delivery to the sugar mills with consequent losses in sugar recovery and increased transport costs. The self-defoliating trait, in which the leaves fall naturally as the cane matures, offers the potential to facilitate green cane harvesting. The effects of the self-defoliating character on cane production and sugar concentration had not been determined. Trials were superimposed on commercial cane of two cultivars (CC 85-63 and V 71-51), in which leaves were artificially removed to simulate the self-defoliating character. The two cultivars responded differently to the leaf removal treatments. CC 85-63 with only four leaves per stem produced similar levels of cane with similar sugar concentration to the controls with 10 leaves per stem. In V 71-51, cane production decreased as leaf number per stem decreased from eight leaves per stem found in the controls. Nevertheless, in both cases, high levels of productivity of more than 16 t recoverable sugar/ha in 13 months were obtained with only four leaves per stem in both cultivars. In CC 85-63, net photosynthetic rate of individual leaves increased as leaf number per stem was reduced, whilst in V 71-51 no compensation was observed. Lodging in both cultivars tended to be less as leaf number per stem decreased. The results indicate that breeders can develop self-defoliating cultivars with a minimum of 4 to 6 leaves per stem, which are highly productive in terms of total sugar production and which also maintain acceptable levels of recoverable sugar.