OPTIMIZING HARVEST DATE IN SUGAR PRODUCTION - A CASE-STUDY FOR THE MOSSMAN MILL REGION IN AUSTRALIA - I - DEVELOPMENT OF OPERATIONS-RESEARCH MODEL AND SOLUTION

Cane and sugar yields within a sugar mill region can vary with geograp hical location, harvest date, harvest age, variety and crop class. It is not possible, due to limited mill capacity, to harvest all cane whe n maximum yields are attained. Given a prolonged harvest season, an im portant question is how the harvest of individual paddocks of cane sho uld be scheduled so as to maximise net revenue for the entire mill reg ion. This paper presents the application of an optimisation model to t he Mossman mill region with the objectives of maximising sugar yield a nd net revenue in relation to harvest date and crop age. Six years of block productivity data classified according to district, crop class, variety, harvest date, harvest age, cane yield and sugar yield, were u sed to generate the input parameters for the model. Other inputs were sugar price, growing and milling costs, and transport and crushing cap acity. With current crushing capacity and harvest season lengths, an a pplication of the model to maximise sugar yield showed a 4% increase i n sugar yield compared to current practice, but a 23% decrease in net revenue due to a shorter crop cycle with less ratoons before replantin g. Optimising with respect to net revenue, gave a 3% gain in sugar yie ld with an 8% gain in net revenue. When crushing capacity was allowed to increase for current season lengths, the model showed a 14% gain in net revenue given fixed milling costs. It is concluded that there is scope for optimising harvest date to improve profitability in this mil l region given current harvest season lengths and land area. (C) 1998 Elsevier Science B.V.