OPTIMIZING HARVEST DATE IN SUGAR PRODUCTION - A CASE-STUDY FOR THE MOSSMAN MILL REGION IN AUSTRALIA - II - SENSITIVITY TO CROP AGE AND CROPCLASS DISTRIBUTION

Optimisation of harvest date in sugarcane production has been shown to increase productivity and profitability. This paper assesses the sens itivity of these responses to crop class and age distribution at harve st, using the Mossman mill region as a case study. Analyses were condu cted to assess the consequences of different number of ratoons before ploughing out various fixed crop ages at harvest; and the advantages o f fallowing before planting compared to ploughout and immediate replan t. Productivity and profitability were found to be sensitive to modifi cations in model input parameters and constraints. The optimal number of ratoons to maximise both sugar yield and net revenue was found to b e three. While the optimal cane supply was not very sensitive to const raints on crop age when it was restricted to 12 months plus or minus 2 , there was a significant reduction in net revenue (4 to 5%) when rest ricted to younger and older crops (9 to 13 and 11 to 15 months). Compa risons of fallow verses ploughout replant showed a gain of 16% in net revenue when all crops were immediately planted after ploughout. This suggests that current fallowing practices are not financially benefici al in the case study region of coastal Mossman. The analysis methodolo gy can be applied in other regions to identify better ways of scheduli ng cane supply. (C) 1998 Elsevier Science B.V. All rights reserved.