The manipulation of irrigation and drying-off schedules of sugar cane to increase sucrose yields
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Perusal of sugar cane production records in the sugar cane belt located in the low-veld of Zimbabwe indicated that sucrose yield was generally lower when water was abundant compared to drought years. It was therefore hypothesized that sucrose yield would be increased by restricting irrigation compared to current practice. Three irrigation treatments, namely, irrigating at crop factor t.00 (current practice), irrigating at crop factor 0.85 and Irrigating at crop factor 0.70, were tested in factorial combination with three drying-off treatments: drying- off to 55 per cent moisture depletion (current practice), to 60 per cent and, to 65 per cent moisture depletion. The experiment was laid out as a split-plot. A standard cane variety NCO 376, which forms 97 per cent of the area under cane was used in the experiment. The results clearly indicated that it is possible to manipulate sucrose concentration and hence sucrose yield by restricting the amount of water applied to the sugar cane crop. Highest sucrose concentration and sucrose yield per hectare was achieved by irrigating at crop factor 0.85 and drying-off to 60 per cent depletion. It is concluded that inducing mild stress by restricting water to levels that do not fall below crop factor 0.85 will increase sucrose yield in the low-veld.