Optimum utilisation of low-capacity combine harvesters in high-yielding wheat farms using multi-criteria decision making

About 23% of wheat farms in Iran have yields of more than 5 t ha −1, but the technology and the capacity of over 85% of the existing combine harvesters are low and they are not suitable for handling such high yields mainly because of their high harvest losses due to high feed rates. Therefore, it is necessary to match machines with the farms by optimising their feed rate either by changing the effective width or the ground speed. However, simply reducing the effective width, which is the most common method, may also lead to a higher seed breakage (SB). A proper technical framework was developed for harvesting such fields with current combine harvesters, based on multi-criteria decision making (MCDM) technique. Several aspects mainly, SB, total harvest losses, fuel consumption, and combine field capacity were considered as harvesting attributes. Nine different combinations of ground speed and effective width were defined as harvesting candidate alternatives. The MCDM technique indicated that simply reducing the effective width is not the most suitable solution for this problem. For example, the optimum solution for a field with the average yield of 7.4 t ha −1 was to use a speed 3.5 km h −1 and the full platform width.