PASTURES IN HAWAII

Agriculture was the main industry in Hawaii for over 100 years. However, over approximately the last 40 years revenues from tourism and military spending have far exceeded those for agriculture. In 1994, the total value of all crops and forest products in Hawaii was estimated to be $425,819,000. With livestock sales, the value was $502,461,000. The revenue from sugar has declined rapidly in recent years with the closeure of the majority of the plantations on all islands except Maui. Although sugarcane remains the number one crop in Hawaii in dollar value, total revenues from sugar have declined dramatically in the past ten years. It is difficult to estimate the amount of land devoted to pasture because this use has expanded into areas formerly planted to sugarcane. The return from pastures can be estimated from the value of beef raised on grass and this figure has also declined in recent years as the industry has moved from marketing animals locally to outshipment of young feeder animals. The current value of cattle was about $20,000,000 in 1994.

Total land area on the islands and its utilization may be found on the Hawaii Agricultural Statistics Service website.

PASTURE MANAGEMENT

Grazing animals were brought to Hawaii soon after its discovery although the first such animals were probably goats rather than cattle. These animals first grazed native grass species, which were not well adapted to grazing. Alein forage species were introduced to provide feed for livestock and have now completely replaced native species in pasture and ranch lands.

Low inputs generally are used on pastures in Hawaii. With fertilization, the use of improved species, and rotational grazing to maintain an optimum balance between grasses and legumes, pastures can be very productive. An intensive and innovative grazing management system (the Savory system) was introduced to Hawaii some years ago and is said to be paying off well for ranchers who have adopted it. With this system, a pasture is divided into a large number of relatively small units, each of which is grazed intensively for one or two days by a large number of cattle and then is rested to permit the grass to regrow. With this system, a higher proportion of the edible forage is harvested and the forage generally is of higher overall quality than in a less intensively managed system. Also, manure is more uniformly distributed over the pasture so nutrients are recycled more uniformly. Animal gains per unit of land area (pounds animal produced per acre per unit of time) are said to be higher with this system than with conventional management systems.

Pastures in Hawaii for the most part are on lands too rough or dry to be utilized for other crops. Grazing lands occur from sea level to about 2,500 meters (8,000 feet) elevation. Many grass and legume species are grown in Hawaii and each has been introduced into a particular climatic niche. At lower elevations, grass species from tropical Africa such as pangola and kikuyu grasses dominate and they are commonly grown with legumes such as desmodium and siratro, which were introduced from South America and Australia. At the higher elevations, tropical species are replaced by species from the temperate zone that are better adapted to the cooler environments. Good quality pastures are generally composed of a mixture of grasses and legumes because the legumes supply some nitrogen to the grass and increase the forage protein content.

Because pastures are managed at low intensity, tillage is only used to aid in the establishment of new species into an existing pasture. Tillage may consist of spraying strips with herbicide to eradicate existing species and opening a furrow into which the new species is planted. At best, modest amounts of fertilizer are applied to pastures so the main source of nutrients would be those recycled in animal manure. Pasture improvement includes the eradication of brush and weeds using herbicides and biological controls and the introduction of improved species that are more productive, more palatable, or of better quality. On intensively managed pastures, fertilizer may be applied to maintain a high level of productivity and forage quality.

Climate influences the productivity of pasture lands, with the most important factor in Hawaii being rainfall. The carrying capacity, in number of animals per acre, of pasture is determined by total rainfall, its seasonal distribution, soil fertility, and forage quality. Because animals require feed all year, the sustained carrying capacity of the pasture is determined by plant productivity during the driest months. Productivity of pastures in the A, B, and part of the C vegetation zones (see Vegetation Zones in Hawaii) peak during the winter rainy season. In areas having high rainfall animal productivity is low during the winter rainfall period. It is not known whether this low productivity is due to poor quality forage or to animal physiology.

On a well managed pasture with good water supply, good fertility, and good quality forage species, the carrying capacity can be as high as 3 or more animals per acre. As environmental resources and forage quality decline, animal carrying capacity may drop to as low as 0.05 which is equivalent to one animal per 20 acres. On good quality pastures, animal growth is rapid, due in part to the fact that the animal doesn't have to work as hard at obtaining food. On a mixture of Desmodium intortum 'Greenleaf' and pangolagrass, animal gains of up to 600 pounds per acre per year have been achieved and the beef graded out as USDA good or choice. Another important legume in dry areas is haole koa (Leucaena leucocephalla, and there is now interest in hybrid leucaneas that are more productive and resistant to psyllid attack.

A major problem in increasing pasture carrying capacity is that much of the pasture land is greatly dissected. The rough terrain makes it difficult to alter species composition or apply fertilizer. Also, because of the extensive land area involved, even the application of small amounts of nutrients require very large amounts of capital. Another factor which contributes to a rancher's reluctance to improve pastures is the relatively low rate of return from grazing lands. However, livestock can graze and provide an income from land that is unsuited for any other form of agriculture.

Crop Hazards

The primary hazard in grazing areas is weeds that are unpalatable to livestock, or sometimes poisonous, and that occupy space that could be growing grass. Biological control is the most common method of keeping weed pests in check where extensive infestations occur. The best examples of success are the almost complete control of prickly pear cactus by the Cactoblastus moth that lays its eggs in the ovary of the flowers. The larva eat the developing ovules, thus preventing most seeds from reaching maturity. The other weed pest controlled by an insect is Lantana camara, an escaped ornamental plant that became widespread in pasture areas. Where potentially problem weeds exist in localized areas, herbicides may be used to prevent further spreading of the infestation.