Slash and burn agriculture is a widely used method of growing food in which wild or forested land is clear cut and any remaining vegetation burned. The resulting layer of ash provides the newly-cleared land with a nutrient-rich layer to help fertilize crops. Fire was the primary tool used by Hawaiians to clear lands prior to cultivation. This was true in areas adjacent to irrigated valleys and windward slopes as well as in the great field systems. Fire may have been repeatedly used to periodically clear the secondary growth on fallow fields.
Fire was later used in the harvesting of sugarcane. Burning the cane before harvesting removes most of the dead vegetation without causing significant damage to the interior of the cane stalk. The sugarcane plant consists of about 75 percent to 80 percent net cane (stalks) from which the juice is extracted and the sugar crystalized. The other 20 percent to 25 percent of the plant consists of leafy material, including tops, from which little or no sugar is produced. This leafy material is called trash. Burning sugarcane before harvest (or milling) removes from one-half to two-thirds of this trash that would otherwise contribute nothing to sugar production.