SUGARCANE IN HAWAII
Total land area on the islands and its utilization are shown in the following two tables.
Land area in Hawaii by island. __________________________________________________________ Island Square miles Acres __________________________________________________________ Hawaii 4,038 2,584,000 Maui 729 466,000 Oahu 698 388,000 Kauai 553 354,000 Molokai 261 167,000 Lanai 139 89,000 Niihau 73 46,000 __________________________________________________________
Land use in Hawaii, 1993 estimates. _________________________________________________________________ Use Acres* _________________________________________________________________ Urban, industrial, military 123,000 Parks 246,000 Waste land (lava, canyons, mountains) 698,000 Forest (not grazed by animals) 1,487,000 Pastures 132,000 Other 63,000 Agricultural crops Sugarcane 121,100 Pineapple 22,300 Vegetables and melons 5,300 Fruits (excluding pineapple) 6,600 Coffee 6,800 Macadamia 20,200 All other** 5,500 ________________________________________________________________*Statistics of Hawaiian Agriculture, 1994
**taro, seed corn, flowers, ornamentals, feed & forage, nursery products.
Sugarcane (Saccharum species; commercial sugarcane clones are produced by crossing among several species) was brought to Hawaii by Polynesians when they migrated here. The first commercial plantation was established on Kauai in 1835 and the crop was grown in the same area until recently.
Sugarcane was widely distributed in the islands and was grown from near sea level to elevations of over 600 meters (2,000 feet) with rainfall varying from about 400 in low-elevation leeward areas to nearly 4,000 mm (15 to 150 inches) on upper windward slopes. Generally, irrigation is required where average annual rainfall was less than 100" per year. At lower elevations, the duration from planting to harvest is about 24 months while at higher elevations, the crop was grown for up to three years before harvesting.
Field practices for the production of sugarcane are highly mechanized. Most workers in the industry in Hawaii are equipment operators and little manual labor is required. The field practices are summarized in the following sections.
Soil PreparationAfter a cane crop is harvested the soil is tilled in preparation for the next crop. The main tillage operations are plowing to a depth of 18 to 24 inches, followed by discing. In some cases the plow is composed of large diameter discs. Occasionally, subsoiling is required to break up hardpans that form at the bottom of the plow layer. Some preplant fertilizer may be applied prior to discing or plowing.
PlantingPlanting material is hand cut from cane plants less than one year old grown specifically for "seed". Bins of seed are dipped in hot water (120 to 130 oF) and a fungicide solution to control disease. For planting, the bins are mounted on a planting machine which opens a furrow, the seed pieces are dropped and a disc on the machine partially closes the furrow. All of the phosphorus and some nitrogen and potassium for the crop is applied at the time of planting. There is some interest in shifting to transplants to reduce the amount of planting material required.
Water ManagementIrrigation is used on about half of the acreage planted to sugarcane. A few years ago, furrow irrigation was the most common method of water distribution. Although furrow irrigation requires little capital, it is labor intensive and uses water inefficiently. With furrow irrigation, one man could irrigate about 10 acres per day. Drip irrigation has been adopted by the industry in recent years because it makes much more efficient use of irrigation water and of labor. Main lines are installed underground and laterals are put in near the soil surface after each harvest. Water distribution is excellent and the application of small amounts of water at short intervals maintains the soil water content near field capacity. The system is easily automated so one man can irrigate about 100 acres per day.
The efficiencies realized by the use of drip irrigation have resulted in its widespread adoption by the sugar industry. The major problem with drip irrigation is clogging of the small holes through which the water passes into the soil. Because of this problem, filtering of solids from the water and injection of chlorine to control microorganism growth is required for all installations. The irrigation system often is also used to apply supplemental fertilizer, usually nitrogen in the form of aqua ammonia and potassium.
FertilizationAll of the P required for a crop is applied at the time of planting. N and sometimes K are applied after planting either in the irrigation water or by airplane. Granular fertilizers are applied by air with urea being the most common form of N used. Potassium is applied as potassium chloride. All fertilizer is applied in the first 8 to 10 months of the 24 month growing period because large amounts of nutrients late in the crop promote vegetative growth and delay ripening and reduce cane sugar content.
Crop HazardsWeeds are the major crop hazard due to the high cost of control. Weeds are controlled by herbicides applied either from a backpack sprayer, tractor applicator, fixed-wing aircraft or helicopter. Spot spraying in the field to control weeds usually is required only during the first few months of growth. Once the leaf canopy shades the soil, the low light level limits weed growth. Insects and diseases are controlled in the field by biological means, primarily through the use of resistant cultivars but stem borers are also kept under control by predators.
RipeningRipening is required to bring the stalk sugar content to an acceptable level. If the sucrose content is too low, sugar recovery is reduced. Ripening involves slowing vegetative growth while permitting photosynthesis to continue. The result is accumulation of sugar in the stalk to levels of 15 to 20%. Ripening is accomplished by withholding N, by reducing the supply of irrigation water, and by application of chemical ripeners. Most ripening in Hawaii is done by the last method. Chemical ripeners function by retarding growth without inhibiting photosynthesis completely so sucrose produced by photosynthesis is accumulated in the stalk. Chemical ripeners are applied by aircraft equipped with sprayers.
HarvestingAll cane in Hawaii is harvested mechanically and most is harvested with a large push-rake mounted on the front of a crawler-tractor. The cane is burned prior to harvest to remove the dry trash and then pushed into large windrows. The cane is trucked to the mill where it is washed, crushed, and the sugar extracted. The extracted juice is purified and water evaporated to produce 96o Brix (approximately 96% sucrose) sugar.