SIMULATION OF PRODUCTION POTENTIAL OF SELF-DEFOLIATING SUGARCANE CULTIVARS

Cane burning before harvest is increasingly questioned due to environm ental concerns. Harvesting of un-burned or green cane, whether by mech anical or manual means, increases trash delivery to the sugar mills wi th 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 char acter. The two cultivars responded differently to the leaf removal tre atments. CC 85-63 with only four leaves per stem produced similar leve ls of cane with similar sugar concentration to the controls with 10 le aves per stem. In V 71-51, cane production decreased as leaf number pe r stem decreased from eight leaves per stem found in the controls. Nev ertheless, in both cases, high levels of productivity of more than 16 t recoverable sugar/ha in 13 months were obtained with only four leave s per stem in both cultivars. In CC 85-63, net photosynthetic rate of individual leaves increased as leaf number per stem was reduced, whils t in V 71-51 no compensation was observed. Lodging in both cultivars t ended to be less as leaf number per stem decreased. The results indica te that breeders can develop self-defoliating cultivars with a minimum of 4 to 6 leaves per stem, which are highly productive in terms of to tal sugar production and which also maintain acceptable levels of reco verable sugar. (C) 1997 Elsevier Science B.V.