Soils are used for the production of plants and support of animals and as structural material for engineering purposes. Thus, this section has two main parts - management of soils for farming and related uses, which include woodland and wildlife habitat, and management of soils for the construction of highways, the support of buildings, and other engineering uses.
This section discusses the suitability and management of the soils for crops and pasture, for woodland, and for wildlife habitat.
For convenience in planning the management of soils, they are placed in management groups according to their suitability for specific uses. One grouping described in this section is the capability system used by the Soil Conservation Service (21). This system is adapted to soils throughout the country to show their suitability for most kinds of crops. Other groupings described are those for sugarcane, pasture, and woodland and for wildlife habitat. These groupings are adapted to the specialized uses of the soils of the island. In the description of each group the soil features that affect management tare given, as well as estimated yields and suggested practices. Only the soils suited to these specific uses have been placed in these groups. Some of the stony soils and the land types, for example, have not been placed in the sugarcane groups because the are unsuited or are too variable. The "Guide to Mapping Units" lists the groups in which each soil has been placed.
Many factors affect the use of soils for crops and pasture. Some important factors are temperature, relief, drainage, depth of soil, stoniness, availability of water, amount of solar insolation, and accessibility and suitability for use of mechanized equipment. These factors are selected in the grouping of the soils and in the management suggested. Management refers to such practices as soil preparation, selection of crops, application of fertilizer, use of crop residue, and control of soil and water loss. Practices vary between plantations, but in general a high level of management is practiced on the island.
Capability grouping shows, in a general way, the suitability of soils for most kinds of field crops. The groups are made according to the limitations of the soils when used for field crops, the risk of damage when they are used, and the way they respond to treatment. The grouping does not take into account major and generally expensive landforming that would change slope, depth, or other characteristics of the soils; does not take into consideration possible but unlikely major reclamation projects; and does not apply to rice, cranberries, horticultural crops, or other crops requiring special management.
Those familiar with the capability classification can infer from it much about the behavior of soils when used for other purposes, but this classification is not a substitute for interpretations designed to who suitability and limitations of groups of soils for range, for forest trees, or engineering.
In this publication, all of the soils are grouped at two levels, the capability class, and the subclass, The classification is designated in the "Guide to Mapping Units" for all soils on the island, both irrigated and nonirrigated soils. The classification is described in the following pages.
CAPABILITY CLASSES, the broadest groups, are designated by Roman numerals I through VIII. The numerals indicate progressively greater limitations and narrower choices for practical use, defined as follows:
|
Class I |
Soils have few limitation that restrict their use |
|
Class II |
Soils have moderate limitations that reduce the choice of plants or that require moderate conservation practices. |
|
Class III |
Soils have severe limitations that reduce the choice of plants, require special conservation practices, or both. |
|
Class IV |
Soils have very severe limitations that reduce the choice of plants, require very careful management, or both. |
|
Class V |
Soils are not likely to erode but have other limitations, impractical to remove, that limit their use largely to pasture, range, woodland, or wildlife. |
|
Class VI |
Soils have severe limitations that make them generally unsuited to cultivation and limit their use largely to pasture or range, woodland, or wildlife. |
|
Class VII |
Soils have very severe limitations that make them generally unsuited to cultivation and limit their use largely to pasture or range, woodland, or wildlife. |
|
Class VIII |
Soils and landforms have limitations that preclude their use for commercial plants and restrict their use to recreation, wildlife, or water supply, or to esthetic purposes. |
CAPABILITY SUBCLASSES are soil groups within one class; they are designated by adding a small letter, e, w, s, or c, to the class numeral, for example, IIe. The letter e shows that the main limitation is risk of erosion unless close-growing plant cover is maintained; w shows that water in or on the soil interferes with plant growth or cultivation (in some soils the wetness can be partly corrected by artificial drainage); s shows that the soil is limited mainly because it is shallow, droughty, or stony; and c, used in only some parts of the United States, shows that the chief limitation is climate that is too cold or too dry.
In class I there are no subclasses, because the soils of this class have few limitations. Class V can contain, at the most, only the subclasses indicated by w, s, and c, because the soils in class V are subject to little or no erosion, thought they have other limitations that restrict their use largely to pasture, range, woodland, wildlife, or recreation.
Sugarcane is the principal crop on the Island of Hawaii. It is grown on the windward slopes of Mauna Kea and the Kohala Mountains and on the southern slopes of Mauna Loa. Sugarcane generally is not irrigated, except for the acreage on the Kohala, Honokaa, and Paauhau soils at low elevations where the rainfall is relatively low and solar insolation is high.
Sugarcane is harvested every 20 to 36 months, depending on the variety of cane and the climate. Replanting generally is not necessary, because after the cane is harvested the root system sends up new sprouts, or shoots, to produce the next crop. Replanting is common, however, to introduce a new variety, alter the irrigation or field layout, relieve undue compaction of the soil, or change the cropping system.
The sugarcane industry is highly mechanized. The use of heavy equipment permits the production of sugarcane in some areas that otherwise would be considered unsuited for cultivation.
The present method of harvesting sugarcane consists of burning the cane fields to remove excess leaves. Immediately after burning, a mechanical push rake pushes the cane stalks into piles. Large cranes load the stalks into trucks that transport the cane to the mill. These operations disturb the soil and increase the erosion hazard, but the hazard can be minimized by harvesting the crop during periods of low rainfall and by allowing time for regrowth of the crop before periods of high rainfall. Soil erosion can be controlled by constructing grassed waterways, irrigating and planting on the contour, lining ditches and canals, and using diversion ditches (fig. 10).
To establish a new planting of sugarcane, the fields are smoothed, subsoiled, or disk-plowed, and harrowed. If the field is to be irrigated, the irrigation, drainage, and road systems are installed. Terraces, diversions, grassed water ways, and roads are installed in non irrigated areas. After these operations are completed, the seed stalk is planted by machine or by hand. The stalk is planted in the bottom of a machine-opened furrow and covered with a few inches of soil. The furrows are laid out on the contour to minimize erosion. After harvest the common practice is to reshape and repair the furrows, terraces, diversions, roads, waterways, and ditches.
Fertilizer is applied by hand, machine, or airplane or in irrigation water. The soils respond readily to applications of nitrogen, phosphorus, and potassium. Lime is needed on some soils. The kind and amounts of fertilizer are best determined by soil tests, tissue analysis, field trials, and experience.
Insecticides are applied as need to control insects. Weeds are controlled by herbicides and hand weeding.
SUGARCANE GROUP 1
This group consists of well-drained to somewhat excessively drained silty clay loams and silty clays that have slope of 0 to 35 percent. These soils have moderate to moderately rapid permeability, slow to rapid runoff, and a slight to severe hazard of erosion. They hold about 1.5 to .18 inches of water available per foot of soil. Their rooting depth is 36 to 60 inches or more. They receive 20 to 80 inches of rainfall annually. The amount of solar insolation is high. The mean annual soil temperature is 72° F. or more.
These soils are irrigated by sprinkler systems or by furrows from ditches or aluminum and concrete flumes. The furrows have a gradient of 0.5 to 1.5 percent. The field layout and tillage practices are across the slope, nearly on the contour. Diversions and secondary field roads are also across the slope and serve to remove runoff water. Young cane is alternated with old cane in strips. The width of the strips and the spacing of diversions are determined by the kind of soil, the length and gradient of slope, and the intensity and frequency of rainfall.
On soils that have a slope greater than 20 percent, special equipment and special land preparation, planting, and harvesting are required to minimize field damage and soil and water losses.
Yields are 8 to 12 tons per acre per crop.
SUGARCANE GROUP 2
This group consists of well-drained silty clay loams that have a slope of 0 to 35 percent. These soils have moderately rapid to rapid permeability, slow to rapid runoff, and a slight to severe erosion hazard. Their rooting depth is 10 to 60 inches or more. They receive 35 to 180 inches of rainfall annually, and the soils in the lower rainfall areas become droughty during the summer. The total solar insolation is relatively high. The mean annual soil temperature is 72° F. or more.
These soils are not irrigated. The field layout and tillage practices are across the slope, nearly on the contour. The diversions and secondary field roads are also across the slope and serve to remove runoff water. Young cane is alternated with old cane in strips. The width of the strips and the spacing of diversions are determined by the kind of soil, the length and gradient of the slope, and the intensity and frequency of rainfall.
On soils that have a slope greater than 20 percent, special equipment and special land preparation, planting, and harvesting are required to minimize field damage and soil and water losses.
Yields are 7 to 11 tons of sugar per acre per crop.
SUGARCANE GROUP 3
This group consists of well-drained silty clay loams that have a slope of 0 to 35 percent. Some of these soils dehydrate irreversibly into fine sand-size aggregates. Permeability is moderately rapid to rapid, runoff is slow to rapid, and the erosion hazard is slight to severe. The rooting depth is 30 to 60 inches or more. The annual rainfall is 60 to 100 inches. The amount of solar insolation is relatively low, and the mean annual soil temperature is between 68° and 71° F.
These soils are not irrigated. The field layout and tillage practices are across the slope, nearly on the contour. Diversions and secondary field roads are also across the slope and serve to remove runoff water. Young cane is alternated with old cane in strips. The width of the strips and the spacing of diversion are determined by the kind of soil, the length and gradient of the slope, and the intensity and frequency of rainfall.
On soils that have a slope greater than 20 percent, special equipment and special land preparation, planting and harvesting methods are required to minimize field damage and soil and water losses.
Yields are 6 to 9 tons of sugar per acre per crop.
SUGARCANE GROUP 4
This group consists of moderately well drained to well drained silty clay loams that have a slope of 0 to 35 percent. Some of these soils dehydrate irreversibly into very hard, fine gravel-size aggregates. Traficability is poor. Permeability is rapid, runoff is slow to rapid, and the erosion hazard is slight to severe. The rooting depth is 10 to 60 inches or more. The annual rainfall is 80 to 300 inches or more. The amount of solar insolation is low, and the mean annual soil temperature is between 56° and 70° F.
These soils receive more than adequate rainfall to produce sugarcane without irrigation. The field layout and tillage practices are across the slope, nearly on the contour. Young cane is alternated with old cane in strips. Diversions and secondary field roads are also across the slope and serve to remove runoff water. The width of the strips and the spacing of the diversions are determined by the kind of soil, the length and gradient of slope, and the intensity and frequency of rainfall. Harvesting is scheduled during the dry moths to minimize field damage and to allow the regrowth of sugarcane before the wetter season begins.
On soils that have a slope greater than 20 percent, special equipment and special land preparation, planting, and harvesting are required to minimize field damage and soil and water losses.
Yields are 6 to 9 tons of sugar per acre per crop.
Truck crops, papaya, bananas, macadamia nuts, and coffee are some of the important crops grown in addition to sugarcane. In 1967 about 18, 540 acres were used for such crops. About one-fourth of this was used for coffee and one-fourth for macadamia nuts.
Truck crops - Lettuce, cucumbers, tomatoes, snap beans, daikon (white radish), and Chinese cabbage (fig. 11) are grown for the Honolulu market, for home use, and to supply other areas when vegetables are out of season. Broccoli, corn, eggplant, peppers, ginger root, onions, and taro are also grown, but in small quantities. Vegetables are grown mainly in the Waimea, Kona, and Volcano districts. Because of the tropical climate, there is an all-year growing season, and in most areas at least two crops of vegetables can be grown in a year.
In preparation for truck crops, the soil is first disk harrowed to chop plant residue. This is followed by plowing, disking, harrowing, and smoothing. Areas of extremely stony mucky soils are cleared with a dozer, then smoothed and rolled. Sugarcane bagasse is spread over the area for a mulch. Soil fumigants are used before planting to control nematodes.
The soils used for vegetables respond readily to nitrogen, phosphorus, and potassium. The amount and kind of fertilizer and the time to apply it depend on the soil and the crop. Fertilizer is applied in dry form or by foliar application. Minor elements and lime are added as needed. The rate and kind of fertilizer to apply are best indicated by soil tests, field trials, and experience.
Vegetable crops are irrigated by overhead sprinklers or by furrows, and they generally require frequent irrigation.
Weeds are controlled by pre-emergence herbicides soon after planting. Contact herbicides are applied after the crop begins to grow. Mechanical and hand weeding are also common methods of weed control.
Insects and fungus are controlled by seed treatment and by insecticides applied by spraying or dusting.
Papaya - This is a herbaceous plant commonly referred to as a tree. It has a single, erect, hollow stem surmounted with a crown of large leaves. The melonlike fruit is spherical to oblong in shape.
The tree grows rapidly, requiring only 10 to 14 months from the time of germination of the seed to the harvesting of the first ripe fruit.
Papaya grows well along the coastal plains and the foothills where temperature and solar insolation are high. Most of the papaya plantings are in the Kapoho area where the soils are extremely stony and shallow over fragmental Aa lava. The solo papaya is the most common variety grown.
Preparation for planting consists of clearing the forest of ohia trees, shaping and smoothing, and rolling with a heavy roller or drum. On fragmental Aa, a small hole is made and a few handfuls of soil are placed in the hole together with fertilizer and a few seeds. Plantings are usually spaced 8 by 10 feet apart.
Weeds are controlled by herbicides. A complete fertilizer is applied at planting time and at intervals of 2 or 3 months.
Control of insects and plant diseases is essential for maximum yields. Phytoptera and anthracnose are the principal diseases of papaya. Mites and fruit flies need to be controlled. Yields are 40,000 to 60,000 pounds per acre per year.
Bananas - Bananas are among the most commonly grown fruits in Hawaii. Commercial banana plants generally do not produce seeds. New plants are usually started from large suckers removed from the parent plant or from sections taken from old banana stumps. The time required to grow a crop is normally one year but depends on climate, soil, and other factors.
The two most important commercial varieties grown are Cavendish (Chinese) and Gros Michel (Bluefield). Bananas require adequate moisture throughout the year and good drainage.
The Cavendish banana can be planted as close as 6 to 8 feet apart, but the Bluefield requires a spacing of 12 to 18 feet. A surface mulch and shallow cultivation help to control weeds. Supplements of manure or commercial fertilizers are applied three or more times a year, the rate depending on the kind and depth of soil, the amount of rainfall, and the size of plants.
Excess suckers are removed at least four times a year. If soil fertility is high, a new sucker can be allowed to develop every 3 months so that no more than four stalks make up a mat at any one time.
Windbreaks are planted to protect bananas in areas exposed to the trade winds. The fruit fly and other insects, in addition to nematodes, diseases, and rats, must be controlled. Bananas ripen best when they are picked green. Yields are about 20,000 pounds per acre per year.
Macadamia nuts - Macadamia nuts are produced in the Hamakua and Kau districts and on lava soils in Hilo, Puna, and Kona. Macadamia trees grow at an elevation from sea level to about 2,500 feet (fig. 12). These trees grow in deep soils as well as in shallow soils over Aa lava (fig. 13). They grow best where the annual rainfall is 50 to 120 inches (8).
Only grafted trees of the best varieties should be planted in new orchards. The three most promising varieties are Kakea, Ikaika, and Keauhou. Macadamia trees take about 7 years to come into commercial production. Yields vary from 2,500 to 3,500 pounds per acre, depending on climate and soil.
A complete fertilizer is applied three to five times a year, the amount and frequency depending on soil, amount of rainfall, and size of plants.
Herbicides are used to control weeds. Control of anthracnose, nut borer, and rats is also essential.
Coffee - The production of coffee is the island's third largest industry. Coffee is grown primarily on the Kona coast at an elevation of 800 to 2,500 feet (fig. 14). The annual rainfall is 40 to 125 inches and occurs mostly during the summer.
Guatemala (Coffea arabica) is the main variety planted. Seedlings are planted about 6 feet apart. The trees produce coffee berries after 3 years and may continue to bear for many years. Yields are about 20 to 25 bags of parchment per acre per year.
A complete fertilizer is applied about three times a year. Herbicides are used to control weeds.
(T. A. Bown, plant materials specialist, SCS, assisted in preparing this section.)
Approximately 743,000 acres are used for cattle grazing on the Island of Hawaii. Ranches vary in size from 250,000 acres to small units operated by part-time ranchers. Nearly all ranches are cow-calf operations. The beef animals are generally marketed as yearlings, although some weaners are sold as feeders.
Suggested practices - In areas of low rainfall, forage production varies extremely from year to year. When the rainfall is adequate, the green-feed period sometimes lasts from November to July. When the rainfall is low, the green-feed period is much shorter, and when there is a drought the grasses sometimes do not green up. In areas of higher rainfall, forage production is consistent from year to year. Those who manage pasture should consider the length of the green-feed period and make full use of the feed when it is most nutritious. They should also consider the consistent variation in forage production from season to season and vary the stock numbers and grazing time accordingly.
Livestock graze selectively. They seek the more palatable and nutritious plants. If grazing is not controlled, the desirable plants will be eliminated and less desirable plants will increase. Pasture rotation, periodic deferment of grazing, and a good fertilization program will help maintain the desirable forage plants.
Weeds can be controlled by applying chemicals, by clipping or mowing, or by controlled grazing.
Carefully controlled grazing of newly seeded pasture is necessary to prevent destruction of the seedlings. During the first year it is desirable to allow bunch grass to produce a seed crop.
Stockwater ponds and troughs, properly located and constructed, help to control grazing (fig. 15). The ponds should be lined with impervious material to prevent seepage.
Most pasture eventually needs reseeding, depending on the kind of plants and management.
Establishing pasture is expensive. If pasture is to be seeded, the native rain-forest vegetation is bulldozed (fig. 16) and a seedbed is prepared. If preparing a seedbed is impractical, pasture can be established by controlling the existing vegetation. Chain dragging, brush raking, controlled burning, and applying chemicals are methods of controlling vegetation. On shallow soils over Aa or pahoehoe lava, the surface layer of organic matter should not be removed. Establishing pasture on extremely stony soils is difficult, because seeding, fertilizing, and controlling weeds and brush must be done by hand or by aerial methods. Stony soils are placed in the same management groups as nonstony soils, however, because the adapted pasture plants and the methods of maintaining the pasture are the same.
Nitrogen or a nitrogen-phosphorus fertilizer is generally necessary to establish grasses. Phosphorus or a combination of phosphorus and lime is usually necessary to establish grasses. Phosphorus or a combination of phosphorus and lime is usually necessary to establish a grass-legume pasture. These should also be applied periodically to maintain yields. The application rate and timing depend on the kind of pasture plants, the soil, the climate, and the season of use.
The best planting stock available should be used for seeding pasture. Clean seed that has a high percentage of germination insures a good stand. Legumes should be inoculated with the proper rhizobium.
All of the present improved varieties of pasture plants on the island have been introduced. In the following paragraphs some improved grasses and legumes are discussed.
Improved grasses and legumes - Koa haole (Leucaena leucocepahla) is a deep-rooted, leguminous, long-lived shrub or small tree. It is adapted to areas that receive 25 to 60 inches of rainfall annually and are at an elevation from sea level to 1,500 feet. Koa haole is established from seed. For best results it should be mechanically planted in a prepared seedbed. It can be planted with guineagrass or green panicgrass, and it should be managed according to the growth cycle of the companion grass.
Big trefoil (Lotus uliginosus) is a long-lived, semiprostrate legume that produces rhizomes and a large fibrous root system. It has a weak, succulent stem that roots at the leaf axis. The stem grows to a length of more than 36 inches. This legume is adapted to areas that receive more than 60 inches f rainfall annually and are at an elevation above 1,000 feet. It grows in open sunlight or partial shade. It can be established from seed or sprigs and can be planted with kikuyugrass or pangolagrass. Big trefoil ahs a regrowth cycle of 30 days during the warmer months and 45 days during the cooler months. It can withstand grazing to a 2-inch stubble if the grazing is rotated.
Intortum (Desmodium intortum) is a long-lived legume that has a long, decumbent stem. The stem sometimes roots at the leaf axis and forms new plants. Intortum is adapted to areas that receive 60 to 120 inches of rainfall annually and are at an elevation from sea level to 3,000 feet. It can be established from seed or sprigs. For best results the seed should be mechanically planted in rows in a prepared seedbed. This legume is generally planted with pangolagrass but is managed according to its own growth cycle. When the leaves have been stripped from the stems, cattle should be removed from the pasture and the intortum allowed to regrow. The regrowth cycle is about 60 days in summer and 90 days in winter.
Kikuyugrass (Pennisetum clandestinum) is a long-lived, deep-rooted, sod-forming grass that spreads by stolons and forms a dense turf. This is an excellent grass for pasture and for controlling erosion. It is adapted to all elevations that receive 40 to 80 inches of rainfall annually. Kikuyugrass is established from sprigs. It has a regrowth cycle of 30 days during the warmer months and 45 days during the cooler months. It can be grazed to a 2-inch stubble.
Pangolagrass (Digitaria decumbens) is a long-lived grass that grows 2 to 3 feet tall and produces long stolons that root at the nodes and form an open turf. It is a good forage producer and provides excellent ground cover that helps control erosion. This grass is adapted to areas that receive 60 to 120 inches of rainfall annually and are at an elevation from sea level to 3,000 feet. Pangolagrass does not produce viable seed. It is propagated by sprigging. For best results the sprigs should be planted less than 2 inches deep in a prepared seedbed. Established pangolagrass has a regrowth cycle of 30 days during the warm months and 45 days in the cool months.
Guineagrass (Panicum maximum) is a long-lived bunch grass that grows 6 to 8 feet tall. It is adapted to areas that receive 25 to 60 inches of rainfall annually and are at an elevation from sea level to 2,000 feet. The large, fibrous root system is a good soil binder and helps control erosion. Guineagrass is easily established from seed in a prepared seedbed. Thin stands can be improved by deferred grazing that permits the growth of a seed crop. Established guineagrass pasture is ready to graze 40 to 60 days after the end of the dry season. If soil moisture is sufficient, guineagrass can be grazed on a 60 day rotation during the hot months and a 90 day rotation during the cool months. To maintain a good stand, this grass should not be grazed closer than 8 to 10 inches.
Paragrass (Brachiaria mutica syn. Panicum purpurascens) is a long-lived, sod-forming grass. It has a coarse, trailing stem that roots at the nodes. The flower stem grows as much as 6 feet tall. Paragrass is particularly adapted to poorly drained soils that are at an elevation of less than 2,000 feet. This grass is a poor seed producer and is usually propagated from sprigs. Established paragrass has a regrowth cycle of 60 days during the warmer months and 90 days during the cooler months. Locally, it is used mainly as green-chop forage.
White clover (Trifolium repens) is a shallow-rooted, creeping, perennial legume that has trifoliolate leaves and stolons that root at the nodes. It is adapted to areas that receive 35 to 80 inches of rainfall. It grows at an elevation from sea level to 10,000 feet but is commonly grown at 2,000 to 7,000 feet. White clover is always established from seed and should be planted in a prepared seedbed with a mechanical planter. This is an excellent pasture legume, but good management is required to keep it in the pasture mixture. It has a regrowth cycle of 30 days in the warm season and 45 days in the cooler months.
Dallisgrass (Paspalum dilatatum) is a deep-rooted, long-lived perennial semibunch grass that has short rhizomes. It is adapted to areas that receive 3o to 100 inches of rainfall annually, and it grows at an elevation from sea level to 6,000 feet. It is best established from seed in a prepared seedbed. Dallisgrass is particularly good for erosion control. It grows best during the warm season and has a regrowth cycle of about 40 days.
Cocksfoot, or orchardgrass (Dactylis glomerata) is a long-lived bunch grass adapted to areas that receive 40 to 100 inches of rainfall annually and are at an elevation of 3,000 to 8,000 feet. Cocksfoot has a large fibrous root system that helps control erosion. It is easily established from seed. It should be planted mechanically less than 1 inch deep in a prepared seedbed. It can be planted with a companion legume. The companion legume can be seeded as recommended or mixed and planted with the cocksfoot seed. Cocksfoot generally has a regrowth cycle of 30 days during the warmer season, but as much as 60 days during the cooler season. In drier areas the stands can be improved by deferred grazing that allows the growth of a seed crop.
Perennial ryegrass (Lolium perenne) is a short-lived, perennial bunch grass that forms a turf under grazing. It is adapted to areas that receive 40 to 100 inches of rainfall annually and are at an elevation of 2,500 to 7,000 feet. The plant is always established from seed and should be planted in a prepared seedbed. Perennial ryegrass has a regrowth cycle of 30 days during its most rapid growth, but it may require 45 days during cool weather.
Buffelgrass (Cenchrus ciliare) is a long-lived bunch grass, well suited to areas that receive 10 to 40 inches of rainfall annually and are at an elevation of less than 2,000 feet. This grass has a large, fibrous root system that helps control erosion. It is readily established from seed, and is best established by shallow seeding with a mechanical planter in a prepared seedbed. Thin stands can be improved by deferred grazing that allows a seed crop to grow. Buffelgrass is ready to graze from 21 to 30 days after rain. If enough soil moisture is available, this grass can be grazed on a 30-day rotation, but it should never be grazed closer than 2 to 3 inches.
Green panicgrass (Pacnicum maximum var. trichoglume) is a medium-tall (3 to 6 feet), long-lived bunch grass. It is adapted to areas that receive 22 to 60 inches of rainfall annually and are at an elevation of less than 2, 000 feet. This productive forage plant makes a good ground cover that helps to control erosion. It is easily established from seed. For best results it should be mechanically planted in a prepared seedbed. This grass has excellent seedling vigor and establishes faster than guineagrass. Grazing can be deferred to produce a seed crop or to provide forage during the dry season. Established green panicgrass pasture is ready to graze 30 to 40 days during the cool months. Green panicgrass should not be grazed closer than 4 to 6 inches.
PASTURE GROUP 1
In this group are soils of the Kawaihae series. These soils occupy leeward coastal areas in the drier parts of the island. They have a slope of 6 to 12 percent. They are at an elevation ranging from sea level to 1,500 feet. And receive from 5 to 20 inches of rainfall annually, most of which occurs during the winter. The mean annual soil temperature is between 74° to 77° F.
These soils formed in volcanic ash. They are extremely stony, somewhat excessively drained, and 20 to 40 inches deep over basalt. They are moderately permeable.
Unimproved pasture consists mostly of Hawaiian piligrass, feather fingergrass, swollen fingergrass, ilima, uhaloa, zinnia, and kiawe. Kiawe trees grow in thick stands along the coastal flats and in open stands on the uplands. During the summer the main source of food along the coastal flats is the kiawe pod. Unimproved pasture produces 1,100 to 1,400 pounds of air-dry forage per acre annually. About three-fourths of the forage is produced during the rainy season. During the dry summer months, most of the annuals die and the perennials are dormant.
Forage plants for improved pasture are buffelgrass, white piligrass, and giant bermuda. Buffelgrass is particularly well adapted. It spreads rapidly and provides ground cover that helps control erosion. Improved pasture produces 1,700 to 2,600 pounds of air-dry forage per acre annually.
PASTURE GROUP 2
In this group are Fill land and soils of Kaalualu, Mahukona, Pakini, and Puu Pa series. These soils occupy southern coastal areas of Mauna Loa and low, leeward areas of Mauna Kea and the Kohala Mountains. They have a slope of 2 to 20 percent. They are at an elevation ranging from near sea level to 2,500 feet and receive from 10 to 40 inches of rainfall annually, most of which falls during the winter. The mean annual soil temperature is between 69° and 75° F.
These soils formed in volcanic ash and basic igneous rocks. They are well drained, are moderately to rapidly permeable, and are 20 inches to more than 60 inches deep.
Unimproved pasture on these soils consists mostly of piligrass, sandbur, natal redtop, bermudagrass, ilima, cactus, klu, Japanese tea, kiawe, and fingergrass. Winter forage production is about three times that of summer production. The total annual production is about 700 to 1,300 pounds of air-dry forage per acre.
Forage plants for improved pasture on these soils are guineagrass, buffelgrass, white piligrass, giant bermudagrass, and koa haole. Improved pasture produces 1,400 to 2,600 pounds of air-dry forage per acre annually.
PASTURE GROUP 3
This group consists of soils of the Hawi, Waiaha, and Punaluu series. These soils are on coastal plains and low uplands. Their dominant slope is 0 to 20 percent. They are at an elevation ranging from near sea level to 1,200 feet and receive from 20 to 90 inches of rainfall annually. In the Kona district most of the rainfalls from July through September. The mean annual soil temperature is between 72° and 75° F.
These soils formed in volcanic ash, basic igneous rock, and organic matter. They are well drained and have moderately rapid and rapid permeability. Hawi soils are more than 48 inches deep. Waiaha soils are less than 20 inches deep over pahoehoe lava. Punaluu soils, which formed in organic matter, are less than 10 inches deep over pahoehoe lava.
Unimproved pasture consists mostly of kiawe, koa haole, klu, cactus, lantana, ilima, opiuma, natal redtop, and bermudagrass. On the Hawi and Punaluu soils, about two-thirds of the forage is produced during the winter. On the Waiaha soils, four-fifths of the forage is produced during the summer. The annual production is 1,000 to 1,500 pounds of air-dry forage per acre.
Forage plants for improved pasture are buffelgrass, guineagrass, green panicgrass, and koa haole. Improved pasture produces 2,000 to 3,000 pounds of air-dry forage per acre annually.
PASTURE GROUP 4
This group consists of soils of the Kamakoa, Kamaoa, Waikaloa, and Waimea series. These soils are on the leeward side of Mauna Kea. Their dominant slope is 0 to 20 percent. They are at an elevation ranging from 1,000 to 6,000 feet and receive from 20 to 60 inches of rainfall annually, most of which falls from November through February. The mean annual soil temperature is between 59° and 69° F.
These soils formed in alluvium and volcanic ash. They are well drained or somewhat excessively drained, and are moderately to rapidly permeable. These soils re more than 30 inches deep, except for the Kamakoa soils, which are 20 to 50 inches deep over hard, consolidated sand.
Unimproved pasture consists mostly of cactus, ilima, aalii, bermudagrass, and natal redtop, and the annual production is 1,000 to 2,000 pounds of air-dry forage per acre. About two-thirds of the forage is produced during the rainy season.
Kikiyugrass, green panicgrass, buffelgrass, bermuda grass, white clover, and bur clover are adapted for 4,000 pounds of air-dry forage per acre.
PASTURE GROUP 5
This group consists of soils of the Kohala, Naalehu, Kainaliu, and Kaimu series. These soils are on low uplands and their slope is 0 to 35 percent. They are at an elevation ranging from near sea level to 1,800 feet and receive from 35 to 60 inches or rainfall annually. Their mean annual soil temperature is between 71° and 75° F.
These soils formed in volcanic ash, basic igneous rock, and organic matter. They are well drained and have moderately rapid to rapid permeability. They are more than 36 inches deep, except for the Kainaliu and Kaimu soils. The Kainaliu soils are 20 to 40 inches deep over Aa lava. The Kaimu soils formed in organic matter and are less than 8 inches deep over fragmental As lava.
Unimproved pasture consists mainly of natal red top, bermudagrass, lantana, Christmas berry, guava, Japanese tea, and bush indigo. Monkey pod, silk oak, and ohia trees are also common in some areas. Two -thirds of the forage is produced during the winter, except in the Kona area where four-fifths of the forage is produced during the summer. The annual production is 2,000 to 3,200 pounds of air-dry forage per acre.
Guineagrass, koa haole, kikuyugrass, and kaimi clover are adapted plants for improved pasture, and the annual production is 4,000 to 7,000 pounds of air-dry forage per acre per year.
PASTURE GROUP 6
Tropaquepts are the only soils in this group. These soils are on alluvial valley bottoms. Their slope is 0 to 6 percent. They are at an elevation ranging from near sea level to 500 feet and receive from 60 to 100 inches of rainfall annually. Their mean annual soil temperature is between 72° and 75° F.
These soils formed in alluvium, and they are 20 inches to more than 40 inches deep. Their dominant properties are the result of poor drainage induced by man. These soils have poor workability the are subject to frequent flooding. The depth of to the water table is less than 20 inches.
Unimproved pasture consists mostly of hilograss, honohonograss, and wetland sedges and guava and monkey pod. These soils are on sites that have a 12 month growing season. The annual production is about 3,000 to 4,000 pounds of air-dry forage per acre.
Pangolagrass, kikiyugrass, big trefoil, and intortum are adapted plants for improved pasture. The annual production is 4,000 to 5,000 pounds of air-dry forage per acre.
PASTURE GROUP 7
This group consists of Mixed alluvial land and soils of the following series:
|
Ainakea |
Niulii |
|
Honuaulu |
Ookala |
|
Kona |
Opihikao |
|
Kukaiau |
Paauhau |
|
Malama |
Puna |
|
Moaula |
|
These soils are on low uplands. Their slope ranges from 0 to 35 percent. They are at an elevation ranging from near sea level to 3,500 feet and receive from 60 to 120 inches of rainfall annually. Most of the rainfall on the Honuaulu soils comes during the summer. The mean annual soil temperature is between 63° and 74° F.
Mixed alluvial land is forming in young alluvium and has variable properties. Kona, Malama, Opihikao, and Puna soils formed in organic matter over lava. Kona and Opihikao soils are less than 7 inches deep aver pahoehoe lava. Malama and Puna soils are less than 10 inches deep over fragmental Aa lava. The other soils formed in volcanic ash and are more than 20 inches deep. They are well drained and have moderately rapid permeability.
Unimproved pasture consists of hilograss, glenwoodgrass, yellow foxtail, carpetgrass, and guava. Ohia, silk oak, eucalyptus, and kukui trees also grow on these soils. The pasture sites have a 12-month growing season. The annual production is about 3,000 to 4,000 pounds of air-dry forage per acre.
Pangolagrass, kikuyugrass, big trefoil, and intortum are adapted plants for improved pasture. The annual production is 4,000 to 5,000 pounds of air-dry forage per acre.
PASTURE GROUP 8
This group consists of soils of the Akaka, Kahua, Kehena, Piihonua, and Puaulu series. These soils are on uplands of Mauna Kea, Mauna Loa, and the Kohala Mountains. They are at and elevation ranging from 1,000 to 6,500 feet and have a slope of 0 to 20 percent. They receive from 60 to 300 inches of rainfall annually, and it is well distributed throughout the year. Their mean annual soil temperature is between 55° and 68° F. There is considerable fog and cloud cover, especially during the winter.
These soils formed in volcanic ash and have a depth ranging from 20 inches to more than 60 inches. They are well drained to somewhat poorly drained and rapidly to slowly permeable.
Unimproved pasture consists mostly of yellow foxtail, carpetgrass, ricegrass, glenwoodgrass, rattail, tar-weed, and wetland sedges. Tree fern, koa, and ohia trees grow in uncleared areas. About four-fifths of the forage is produced during the summer. The annual production is 2,000 to 3,000 pounds of air-dry forage per acre.
Kikuyugrass, pangolagrass, big trefoil, white clover, and intortum are among the adapted plants for improved pasture. The annual production is 4,000 to 5,000 pounds of air-dry forage per acre.
PASTURE GROUP 9
This group consists of soils of the following series:
|
Alapai |
Hilea |
Hilo |
|
Honaunau |
Honokaa |
Kaiwiki |
|
Kealakekua |
Keaukaha |
Keei |
|
Kiloa |
Manu |
Ohia |
|
Olaa |
Panaewa |
Papai |
These soils are on uplands and have a slope range of 0 to 35 percent. They are at an elevation ranging from near sea level to 5,000 feet. They receive from 80 to 200 inches of rainfall annually, and it is well distributed throughout the year. The mean annual soil temperature is between 58° and 74° F.
These soils are moderately well drained to well drained and are rapidly permeable. Keaukaha, Keei, Kiloa, and Papai soils formed in organic matter and are not more than 10 or 12 inches deep over pahoehoe or fragmental Aa lava. The other soils formed in volcanic ash and are 20 inches to more than 60 inches deep, except for the Hilea and Panaewa soils, which are less than 20 inches.
Unimproved pasture on these soils consists mostly of californiagrass, carpetgrass, ricegrass, and honohonograss. Ohia, tree fern, waiwi, and melastome grow in uncleared areas. The pasture sites have a 12-month growing season, but the best quality of forage is produced during the summer. The annual production is 3,000 to 5,000 pounds of air-dry forage per acre.
Pangolagrass, kikuyugrass, big trefoil, and intortum are adapted plants for improved pasture (fig. 17), and the annual production is 8,000 to 14,000 pounds of air-dry forage per acre.
PASTURE GROUP 10
This group consists of soils of the Heake, Puukala, Kahaluu, Lalaau, and Puhimau series. These soils are on uplands of Mauna Loa and Hualalai and have a slope range of 0 to 20 percent. They are at an elevation ranging from 2,000 to 7,000 feet and receive from 60 to 150 inches of rainfall annually. Their mean annual soil temperature is between 55° and 65° F.
These soils are well drained and are rapidly permeable. The Heake, Puhimau, and Puukala soils formed in volcanic ash, pumice, and cinders. They are less than 20 inches deep over pahoehoe lava. The Kahaluu and Lalaau soils formed in organic matter and are less than 10 inches deep. The Kahaluu soils are over Pahoehoe lava, and the Lalaau soils are over fragmental Aa lava.
Unimproved pasture consists mostly of carpetgrass, ricegrass, glenwoodgrass, puu lehua, tarweed, and wetland sedges. The main trees are tree fern, koa, mamani, and ohia. About four-fifths of the forage is produced during the summer. The annual production is 500 to 1,500 pounds of air-dry forage per acre.
Kikuyugrass, dallisgrass, orchardgrass, big trefoil, and white clover are adapted plants for improved pasture. The annual production is 1,000 to 3,000 pounds of air-dry forage per acre.
PASTURE GROUP 11
In this group are soils of the Maile, Manahaa, Punohu, and Puu Oo series. These soils are on uplands of Mauna Kea, Hualalai, and the Kohala Mountains. They have a slope of 0 to 20 percent. They are at an intermediate elevation ranging from 2,500 to 6,500 feet and receive from 50 to 100 inches of rainfall annually. Their mean annual soil temperature is between 53° and 60° F. There is considerable fog and cloud cover during the winter.
These soils formed in volcanic ash, and their depth ranges from 20 inches to more than 60 inches. They are well drained and have moderately rapid permeability.
Unimproved pasture consists of bermudagrass, rattail, sweet vernal, kukaipuaa, white clover, and alapaio fern. Koa, ohia, and tree fern grow on uncleared areas. About two-thirds of the forage is produced during spring and fall. The annual production is 4,000 to 6,000 pounds of air-dry forage per acre.
Kikuyugrass, pangolagrass, orchardgrass, ryegrass, white clover, and big trefoil are adapted plants for improved pasture, and the annual production is 8,000 to 12,000 pounds of air-dry forage per acre.
PASTURE GROUP 12
In this group are soils of the Kikoni, Palapalai, Umikoa, Kekake, and Mawae series. These soils are on uplands of Mauna Kea, Kohala, and Hualalai. They have a slope range of 0 to 20 percent. They are at an elevation ranging from 2,600 to 7,000 feet and receive from 35 to 90 inches of rainfall annually. Their mean annual soil temperature is between 52° and 66° F.
All except the Kekake and Mawae soils formed in volcanic ash and are more than 42 inches deep. The Kekake and Mawae soils formed in organic material over lava and are less than 10 inches deep. Kekake soils overlie pahoehoe lava, and the Mawae soils overlie fragmental Aa lava. The soils of this group are well drained and have moderately rapid to rapid permeability.
Unimproved pasture consists mostly of hilograss, carpetgrass, yellow foxtail, bermudagrass, and rattail and an overstory of ohia and tree fern. About tow-thirds of the forage is produced during spring and fall. Short, droughty periods and a lowering of the temperature may influence forage production. The annual production is 2,000 to 5,000 pounds of air-dry forage per acre.
Pangolagrass, kikuyugrass, orchardgrass, big trefoil, and intortum are adapted plants for improved pasture, and the annual production is 6,000 to 10,000 pounds of air-dry forage per acre.
PASTURE GROUP 13
In this group are soils of the Hanipoe, Kapapala, and Laumaia series. These soils are on the high uplands of Mauna Kea and Mauna Loa. Their slope is 0 to 20 percent. They are at an elevation ranging from 2,000 to 8,000 feet and receive from 30 to 70 inches of rainfall annually. Their mean annual soil temperature is between 50° and 61° F.
These soils formed in volcanic ash and have a depth of 36 inches to more than 60 inches. They are well drained and have moderately rapid permeability.
Unimproved pasture consists mostly of bromegrass, rattail, and kukaipuaa and an overstory of koa, ohia, and mamani. Because of the cool temperature and dry periods, forage production is seasonal. It is slightly higher during the summer. The annual production is 2,200 to 3,500 pounds of air-dry forage per acre.
Kikuyugrass, puulehua, orchardgrass, white clover, and big trefoil are adapted plants for improved pasture, and the annual production is 4,200 to 8,000 pounds of air-dry forage per acre.
PASTURE GROUP 14
In this group are soils of the Apakuie, Keekee, Kilohana, and Huikau series. These soils are on high uplands of Mauna Kea and Hualalai. Their slope is 0 to 20 percent. They are at an elevation ranging from 5,000 to 9,000 feet and receive from 15 to 40 inches of rainfall annually. Their mean annual soil temperature is between 47° and 53° F.
All except the Keekee soils formed in volcanic ash, cinders, and pumice. Keekee soils are forming in young alluvium. The soils of this group are 36 inches to more than 60 inches dep. They are well drained or somewhat excessively drained and are rapidly or very rapidly permeable.
Unimproved pasture consists mostly of puakeawe, ohelo, aalii, hardstem lovegrass, mountain pili, and sweet vernal and an overstory of koa, ohia, and mamani. Forage production is slightly higher during spring and fall. The annual production is 1,000 to 1,500 pounds of air-dry forage per acre.
Orchardgrass, alta fascue, tall meadow outgrass, velvetgrass, Parker Ranch bluestem, burclover, and black medic are prospective plants for improved pasture, and the annual production is 2,000 to 4,000 pounds of air-dry forage per acre.
In the 1930's the Civilian Conservation Corps planted trees on the Island of Hawaii, primarily for watershed protection. Many of these stands are now ready to be harvested (fig. 18). According to the "Forest Resources of Hawaii - 1961" (9), the volume of timber on the island was about 602 million board feet, which was about 84 percent of the volume of timber in the State. The "Conservation Needs Inventory of 1967" (unpublished) lists 704,000 acres, or 28 percent of the total acreage of the island, in commercial forest.
The native forests are generally well stocked with ohia, koa, eucalyptus, and other trees. There are about 82 million board feet of robusta eucalyptus, which is used increasingly for furniture manufacturing, home construction, and other purposes (9).
Most of the trees that are planted are for timber, windbreaks, or watershed, but Norfolk-Island-pine is planted for Christmas trees (fig. 19), which are marketed locally and on the mainland.
Woodland conservation - Conservation practices are needed to develop a woodland enterprise on the Island of Hawaii. Before trees can be planted, many areas need clearing to remove competing plants and prepare the soil. On shallow soils over Aa or pahoehoe lava, the organic material should be disturbed as little as possible.
Normally, seedlings are planted in spacings that range form 8 by 8 feet to 12 by 12 feet. To insure tree survival and good form, initial plantings of trees are usually closer than needed.
When the trees are 5 to 20 years of age, the stands are thinned to improve the growth and quality of the crop. Periodic commercial thinning increases income and maintains a fast growth rate of the remaining trees. The trees left for cutting are pruned.
When the stand has reached a desired size, it is harvested by clear cutting or by some type of shelterwood cutting. After the harvest, regeneration of the stand begins, and competing vegetation is removed until the seedlings are well established.
Proper construction of access roads and control of erosion are important. Roads should be constructed on grades of less than 12 percent and protected from erosion by water bars, culverts, and ditches.
Woodland groups - The soils of the island have been placed in woodland groups on the basis of adapted speices of trees, estimated annual productivity per acre, seedling mortality, plant competition, equipment limitations, erosion hazard, and windthrow hazard.
Adapted species are trees that are best suited for planting or for favoring in existing stands. On the Island of Hawaii, most of the trees that are grown commercially are exotics that have been introduced. Ohia and koa are the main native trees that are satisfactory for commercial production.
Estimated annual productivity per acre is the estimated annual production of bard feet per acre measured according to the international one-fourth-inch rule. At present there are no site or yield tables for any species of trees grown in Hawaii, but many stands of trees that have a known age have been measured and yields have been estimated on the basis of harvesting cycle of 30 to 70 years, using robusta eucalyptus as a standard. One reason for the wide range in productivity within a group is the variation in growth rate between species of trees.
Seedling mortality is the mortality of naturally occurring or planted seedlings, as influenced by soil, topography, and climate. The rating is slight if the expected mortality is less than 25 percent, moderate if it is between 25 and 50 percent, and sever if it is greater than 50 percent.
Plant competition is the invasion or growth of undesirable plants. Slight competition does not prevent natural regeneration or the growth of planted seedlings. Moderate competition delays but does not prevent the eventual establishment of adequately stocked stands. Severe competition prevents establishment of stands unless the site is intensively prepared and weeded.
Equipment limitations are limitations imposed by the characteristics of the soils that restrict or prevent the use of equipment in tending and harvesting trees. The limitation is light if it does not restrict the kind of equipment or the time or year in which it can be used. The limitation is moderate if the use of equipment is moderately restricted by slope, stones, seasonal wetness, or physical characteristics of the soils. The limitation is severe if special equipment is needed and its use is restricted by slope, stones, wetness, or soil characteristics.
Erosion hazard depends on slope, soil stability, permeability, water-holding capacity, and extent of past erosion. Erosion in woodland seldom occurs until vegetation is disturbed or destroyed by fire or by excessive grazing, logging, or road building. The hazard is slight if there are only minor problems, moderate if some control measures are necessary and severe if intensive control measures and special equipment are needed.
Windthrow hazard is the possibility of trees being blown over by wind. The hazard is slight if trees are not expected to be blown down by commonly occurring winds, moderate if some trees growing on wet or shallow soil are likely to be blown down by high wind, and severe if most of the trees growing in a stand on wet or shallow soil are expected to be blown down by moderate or high wind.
WOODLAND GROUP 1
This group consists of well-drained and somewhat excessively drained very fine sandy loams that formed in volcanic ash. These soils have a slope range of 0 to 20 percent. They are at an elevation of 1,000 to 6,000 feet and receive 20 to 60 inches of rainfall annually. The mean annual soil temperature is between 59° and 69° F.
Loblolly pine, slash pine, and gray ironbark eucalyptus are the adapted species. The estimated annual production is 100 to 200 board feet per acre. Seedling mortality is moderate to sever. Plant competition is slight from bermudagrass, aali, and cactus. The equipment limitation is slight except in stony areas. The erosion hazard is slight to moderate, and the windthrow hazard is slight.
WOODLAND GROUP 2
This group consists of well-drained silty clay loams that formed in volcanic ash. These soils have a slope range of 0 to 35 percent. They receive from 35 to 60 inches of rainfall annually and are at an elevation of 750 to 1,800 feet. Their mean annual soil temperature is between 71° and 75° F.
The adapted species are saligna eucalyptus, gray ironbark eucalyptus, red ironbark, silk oak, and Norfolk-Island-pine. The estimated annual production is 200 to 400 board feet per acre. Seedling mortality is moderate. Plant competition is moderate from bermudagrass, kikuyugrass, hilograss, and rattail. The equipment limitation is light to moderate, the windthrow hazard is slight, and the erosion hazard is slight to severe.
WOODLAND GROUP 3
This group consists of moderately deep, poorly drained soils that formed in recent alluvium. These soils have a slope range of 0 to 3 percent. They receive from 60 to 100 inches of rainfall annually and are at an elevation of 0 to 500 feet. The mean annual soil temperature is between 70° and 76° F.
Monkey pod, robusta eucalyptus, saligna eucalyptus, and albizzia are the adapted species on these soils. The estimated annual production is 500 to 800 board feet per acre. Seedling mortality is slight. Plant competition is moderate from hilograss, californiagrass, guava, and ferns. The equipment limitation and windthrow hazard are severe. The erosion hazard is slight. These soils are subject to frequent flooding.
WOODLAND GROUP 4
This group consists of well-drained silty clay that formed in residuum from basic igneous rock. Theses soils have slope range of 0 to 35 percent. They receive from 40 to 60 inches of rainfall annually and are at an elevation ranging from sea level to 1,500 feet. The mean annual soil temperature is between 72° and 74° F.
Norfolk-Island-pine, robusta eucalyptus, silk oak, and monkey pod are the adapted species. Estimated annual production is 200 to 400 board feet per acre. Seedling mortality is moderate to severe. Plant competition is moderate from bermudagrass. The equipment limitation is light to moderate, the erosion hazard is slight to severe, and the windthrow hazard is slight.
WOODLAND GROUP 5
This group consists of well-drained silty clay loams that formed in volcanic ash. These soils have a slope range of 0 to 35 percent. They receive from 60 to 120 inches of rainfall annually and are at an elevation ranging from near sea level to 2,500 feet. The mean annual soil temperature is between 65° and 74° F.
Saligna and robusta eucalyptus, Australian toon, Queensland maple, monkey pod, silk oak, Norfolk-Island-pine, and albizzia are the adapted species on these soils. The estimated annual production is 500 to 800 feet per acre. Seedling mortality is slight. Plant competition is moderate from hilograss, californiagrass, guava, Christmas berry, and kikuyugrass. The equipment limitation is slight to moderate, the windthrow hazard is slight, and the erosion hazard is slight to severe.
WOODLAND GROUP 6
This group consists of well-drained to somewhat poorly drained soils that formed in volcanic ash and have a silt loam or silty clay loam texture. These soils have a slope range of 0 to 20 percent and are more than 20 inches deep. They are on uplands at an elevation ranging from 1,000 to 6,500 feet and receive from 90 to 300 inches of rainfall annually. The mean annual soil temperature is between 55° and 68° F.
Robusta eucalyptus, Nepal alder, tropical ash, and the native ohia are the adapted species. The estimated annual production is 500 to 900 board feet per acre. Seedling mortality is slight. Plant competition is severe from tree fern, false staghorn fern, melabar melastome, downy myrtle, and kikuyugrass. The equipment limitation is severe because of the low bearing capacity of these soils. The erosion hazard is slight to moderate, and the windthrow hazard is slight.
WOODLAND GROUP 7
This group consists of well drained and moderately well drained silty loams and silty clay loams that formed in volcanic ash. These soils have a slope range of 0 to 35 percent. They are at an elevation ranging from near sea level to 5,000 feet and receive from 80 to 200 inches of rainfall annually. Their mean annual soil temperature is between 58° and 74° F.
The adapted species are saligna and robusta eucalyptus, Nepal alder, Norfolk-Island-pine, Australian toon, Queensland maple, tropical ash, blackwood, sugi, redwood, and monkeypod. Ohia and koa are native trees that are well adapted. The estimated annual production is 700 to 1,000 board feet per acre. Seedling mortality is slight. Plant competition is severe from tree fern, false staghorn fern, melabar melastome, downy myrtle, and kikuyugrass. The equipment limitation is moderate to severe. The erosion hazard is slight to severe, and the windthrow hazard is slight.
WOODLAND GROUP 8
This group consists of well-drained silt loams that formed in volcanic ash. These soils have a slope range of 0 to 20 percent. They are at an elevation of 2,500 to 6,500 feet and receive from 50 to 100 inches of rainfall annually. Their mean annual soil temperature is between 53° and 60° F.
The adapted species are saligna and robusta eucalyptus, Australian toon, Queensland maple, tropical ash, slash pine, redwood, sugi, and the native ohia and koa. The estimated annual production is 500 to 800 board feet per acre. Seedling mortality is slight. Plant competition is slight, except where kikuyugrass grows. The equipment limitation is slight, except on the very stony soils where it is moderate. The erosion hazard is slight to moderate, and the windthrow hazard is slight.
WOODLAND GROUP 9
This group consists of well-drained very fine sandy loams, silt loams, and silty clay loams that formed in volcanic ash. These soils have a slope range of 0 to 20 percent. They receive from 35 to 90 inches of rainfall annually and are at an elevation of 2,600 to 5,000 feet. Their mean annual soil temperature is between 55° and 66° F.
The adapted species are saligna and robusta eucalyptus, Australian toon, Queensland maple, tropical ash, and loblolly and slash pine. The estimated annual production is 500 to 700 board feet per acre. Seedling mortality is slight. Plant competition is severe from kikuyugrass and paspalum. The equipment limitation is slight, the erosion hazard is slight to moderate and the windthrow hazard is slight.
WOODLAND GROUP 10
This group consists of well-drained loams and silt loams that formed in volcanic ash. These soils have a slope range of 0 to 20. They receive from 30 to 70 inches of rainfall annually and are at an elevation of 2,000 to 4,000 feet. Their mean annual soil temperature is between 52° and 61° F.
The adapted species are saligna eucalyptus, sugi, tropical ash, loblolly pine, slash pine, and the native koa and ohia. The estimated annual production is 400 to 600 board feet per acre. Seedling mortally is light. Plant competition is moderate from alapaio fern, dallisgrass, and kikuyugrass. The equipment limitation is slight, except on very soils where it is moderate. The erosion hazard is slight to moderate, and the windthrow hazard is slight.
WOODLAND GROUP 11
In this group are shallow sandy loams and silt loams that formed in volcanic ash and pumice over pahoehoe lava. These soils are only 10 to 20 inches deep. They have a slope range of 0 to 20 percent. They receive from 60 to 125 inches of rainfall annually and are at an elevation of 2,000 to 4,000 feet. Their mean annual soil temperature is between 59° and 61° F.
Saligna eucalyptus, blackwood, sugi, tropical ash, and Nepal alder are the adapted species. The estimated annual production is 200 to 500 board feet per acre. Seedling mortality is slight. Plant competition is slight to moderate from tree fern and kikuyugrass. The equipment limitation is slight to moderate. The erosion hazard is slight to moderate, and the windthrow hazard is severe.
WOODLAND GROUP 12
This group consists of shallow silty clay loams that formed in volcanic ash and are only 10 to 20 inches deep over pahoehoe lava. These soils have a slope range of 0 to 20 percent. They receive from 100 to 200 inches of rainfall annually and are at an elevation of 300 to 2,000 feet. Their mean annual soil temperature is between 65° and 74° F.
Robusta and saligna eucalyptus, sugi, Australian toon, and the native ohia and koa are the adapted species on these soils. The estimated annual production is 500 to 900 board feet per acre. Seedling mortality is slight. Plant competition is slight to moderate from tree fern, hilograss, californiagrass, and melabar melastome. The equipment limitation is moderate, the erosion hazard is slight, and the windthrow hazard is moderate to severe.
WOODLAND GROUP 13
In this group are mucky soils that formed in organic matter and are less than 10 inches deep over Aa lava. These soils have a slope range of 0 to 20 percent. They receive from 60 to 150 inches of rainfall annually and are at an elevation ranging from near sea level to 4,000 feet. Their mean annual soil temperature is between 63° and 75° F.
Saligna and robusta eucalyptus, blackwood, Queensland maple, Australian toon, and the native ohia are the adapted species. Estimated annual production is 700 to 1,000 board feet per acre. Seedling mortality is slight. Plant competition is severe from tree fern, guava, and kikuyugrass. The equipment limitation is severe. The erosion and windthrow hazards are slight.
WOODLAND GROUP 14
In this group are mucky soils that formed in organic matter and are less than 12 inches thick over Aa lava. These soils have a slope range of 0 to 20 percent. They receive from 50 inches to more than 150 inches annually and are at an elevation of 3,500 to 7,000 feet. Their mean annual soil temperature is between 53° and 59° F.
Saligna and robusta eucalyptus, tropical ash, blackwood, redwood, sugi, and the native ohia and koa are the adapted species. The estimated annual production is 500 to 700 board feet per acre. Seedling mortality is slight. Plant competition is moderate from tree fern and kikuyugrass. The equipment limitation is severe. The erosion hazard and windthrow hazard is slight.
WOODLAND GROUP 15
This group consists of well-drained silt loams that formed in volcanic ash and are 10 to 20 inches deep over pahoehoe lava. These soils have a slope range of 0 to 20 percent. They receive from 20 to 40 inches of rainfall annually and are at an elevation ranging from near sea level to 1,000 feet. Their mean annual soil temperature is between 72° and 74° F.
Silk oak, mango, and monkey pod are the adapted species. The estimated annual production is 100 to 300 board feet per acre. Seedling mortality is severe. Plant competition is severe from guineagrass. The equipment limitation and the erosion hazard are slight to moderate. The windthrow hazard is severe.
WOODLAND GROUP 16
In this group are well-drained and somewhat excessively drained very fine sandy loams, loamy sands, and loamy fine sands that formed in volcanic ash or cinders. These soils have a slope range of 0 to 20 percent. They receive from 15 to 40 inches of rainfall annually and are at an elevation of 5,000 to 9,000 feet. Their mean annual soil temperature is between 47° and 53° F.
Loblolly and slash pine and gray ironbark eucalyptus are the adapted species. The estimated annual production is 100 to 200 board feet per acre. Seedling mortality is moderate to severe. Plant competition is slight from mamani, naio, aalii, and lovegrass. The equipment limitation is slight to moderate, the erosion hazard is slight to severe, and the windthrow hazard is slight.
Various kinds of wildlife thrive on the island, from the arid coastal plains to the very humid rain forests on the mountain slopes. Nearly all the big game and the upland game birds were introduced. The first pigs were brought in by the early Polynesians as a source of food. Goats were introduced by Captain Cook in 1778. Captain Vancouver brought sheep and cattle as gifts to the royalty in 1794. A tabu was placed on them, however, and they went wild in the forest (23).
Since 1920 many kinds of birds have been introduced for hunting, for control of insects, and for esthetic value. Birds that have been brought in primarily for hunting are the Chinese rind-necked pheasant, California valley quail, Japanese quail, Indian chukar partridge, barred dove, and lace-necked dove. The Rio-Grande turkey, Reeves' pheasant, Barbary partridge, Gambel's quail, and francolin partridge have been introduced lately by the State Fish and Game Division of Hawaii (14).
Bass and bluegill are stocked in some reservoirs in Kohala.
Wild pigs are found from sea level to high up in the mountains. Goats are common on rocky areas throughout the island. Feral sheep are concentrated on the high slopes of Mauna Kea and Mauna Loa.
The hunting season extends year round for sheep, goats, and pigs. The game-bird season usually opens during the beginning of November and closes in the middle of January. Bow and arrow hunting for sheep and pigs is open all year in certain areas.
There are five public hunting grounds, or game management areas, on the Island of Hawaii. These are located within four soil associations described in the "General Soil Map" section of this publication.
The Puako game area is and arid habitat in the Kawaihae soil association. The vegetation consists of kiawe, ilima, and piligrass. Pheasants, lace-necked and barred doves, and Gambel's quail are hunted here.
The Mauna Loa game area is the Saddle overlapping the Kekake-Keei-Kiloa and the Lava flows soil associations. The vegetation in the Kekake-Keei-Kiloa soil association consists of ohia and tree fern forest. The Lava flows association has a sparse vegetation of ohelo berry, aalii, and mamani. Wildlife hunted in this area include goats, feral sheep, wild pigs, pheasants, California quail, Japanese quail, chukar partridge, and doves.
The Mauna Kea game area is within the boundaries of the Mauna Kea Sate Forest. The area extends from an elevation of about 6,000 feet to the top of the mountain. It is in the Lava flows soil association. The vegetation consists of ohelo berry, aalii, naio, and mamani trees. Wild pigs, goats, feral sheep, pheasants, quail, chukar partridge, doves, and pigeons live in this area.
The Horse Pasture game area occurs within the Waimea-Kikoni-Naalehu soil association, which has a vegetative cover of grass and brush. This area is open to upland game bird hunting.
The Pohakuloa game area is a semi-arid alluvial flat in the Saddle between Mauna Kea and Mauna Loa. All kinds of birds and big game common on the island are found in limited numbers.
Management of the Soils for Engineering
(Harlan G. Collings, irrigation engineer; and Hugo T. Shogren, State conservation engineer, Soil Conservation Service, assisted in preparing this section).
This section provides information of special interest to engineers, builders, farmer, and others who use soil as structural material or as foundation material upon which structures are built. Among the soil properties most important in engineering are permeability, shear strength, shrink-swell potential, available water capacity, and reaction.
Information concerning these and related soil properties are in tables 2, 3, and 4. The data and interpretations in these tables can be used in:
The engineering data and interpretations reported here do not eliminate the need for onsite sampling and testing, especially on sites that are to support heavy loads or where the excavations are deeper than the soil layers reported here. Even in these situations, however, the engineering data and the soil maps are useful in planning more detailed field investigations and for indicating the kinds of problems that can be expected.
Some of the terms used in this publication have special meanings in soil science that does not correspond with the meanings of the same terms in engineering. These terms are defined in the Glossary according to their meaning in soil science. For additional information, engineers may want to refer to the section describing the soils and the section on classification and formation of the soils.
Engineering classification systems
The two systems most commonly used in classifying soils for engineering are the AASHO system (2), used by the American Association of State Highway Officials, and the Unified system (22), used by the Soil Conservation Service, the Department of Defense, and others.
The soils of this survey are classified according to the Unified Soil Classification System. This system is based on particle-size distribution, plasticity, liquid limit, and organic-matter content. It divides soils into three major groups - coarse grained (eight classes), fine grained (six classes), and organic.
The soils have not been classified in accordance with the AASHO system, which has limited value in classifying the engineering properties of Hawaiian soils. Most of these soils are very fine grained and are in groups A-6 or A-7, but they do not exhibit engineering properties associated with temperate-region soils in these groups.
Estimated properties of the soils
Tables provide estimates of soil properties that are important in engineering. The estimates are based on field classifications and descriptions, on physical and chemical tests of selected representative samples on test data from comparable soils in adjacent areas, and on experience in working with the individual kind of soil in the survey area.
The estimates are given for the soil profile, which is divided into layers that have significantly different engineering properties. The thickness of these layers and the depth from the surface are shown.
The USDA texture is the apparent field texture. By standards of mechanical analysis, most soils described in this publication are clay.
The Unified classification group symbol is shown for each significant layer. If the classification is borderline between two groups, a hyphen is used between the tow symbols, such as "ML-CL." Engineering properties of Hawaiian soils placed in ML, MH, and CL groups may be significantly different from those of other soils in temperate regions in these groups. Hawaiian soils exhibit a higher shear strength and a lower shrink-swell volume with change in moisture content. The difference in these properties is apparently related to the very fine particle size, the microstructure, and the high aggregate stability.
Permeability relates only to movement of water downward through undisturbed soil. It does not include lateral seepage. The estimates are based on soil structure, porosity, and limited permeability tests on undisturbed cores. Flow pans, surface crusts, and other properties resulting from use of the soils are not considered.
Available water capacity is the amount of water available to plants. It is the water retained in the soil between the wilting point and field capacity. These estimates are based on extensive laboratory test, field experience, and soil properties. Estimates of available water capacity are given only for the Hawi, Kikoni, Kohala, Mahukona, Paauhau, and Waimea soils, which are now irrigated.
Reaction is the degree of acidity or alkalinity of a soil, expressed as a pH value. The pH value and relative terms used to describe soil reaction are explained in the Glossary.
Shrink-swell potential is and indication of volume change to be expected of the soil material with changes in moisture content. A high shrink-swell potential indicates hazards to the maintenance of structures built in, on, or with such soil material. Generally, soils classified as CH have a high shrink-swell potential, and those classified as ML and SP have a low shrink-swell potential. Many of the soils classified as OH are in areas of high rainfall and are wet throughout the year. These soils exhibit a high shrink and a low swell potential when used in a dry environment.
Corrosivity indicates the potential danger to uncoated metal or concrete structures through chemical action that dissolves or weakens the structural material. Some structural materials corrode when buried in soil, and they corrode more rapidly in some soils than in others. Extensive installations that intersect soil boundaries or soil horizons are more likely to be damaged by corrosion than are installations entirely in one kind of soil or soil horizon.
Tables interpret the soil properties in terms of suitability or limitations for specific farming and engineering uses. These interpretations are based on the estimates shown in tables, on test data, and on field experience.
The best sources are Aa lava, crushed hard rock, or coral.
Engineering interpretations have not been given for agricultural drainage and irrigation. Drainage is not needed or not applicable on most of the soils of this survey area. Only the Hawi, Kikoni, Kohala, Mahukona, Paauhau, and Waimea soils are irrigated. These soils have moderate or rapid intake rate and moderate or high available water capacity.
Topsoil is a fertile soil or soil material, ordinarily rich in organic matter, used as a topdressing for lawns, gardens, roadbanks, and the like. Soils that have low natural fertility are rated according to their response to fertilization.
Road fill is material used to build embankments. The ratings indicate performance of soil material moved from borrow areas for these purposes.
Highway location is influenced by features of the undisturbed soil that affect construction and maintenance of highways.
Farm pond reservoir areas are affected mainly by soil features that control the seepage of water.
Farm pond embankments serve as dams. They are affected by features of both the subsoil and substratum that are important in the construction of embankments.
Foundations for low buildings are affected chiefly by features of the undisturbed soil that influence its capacity to support low buildings that have normal foundation loads. Specific values of bearing strength are not assigned.
Septic tank filter fields are affected mainly by permeability, slope, depth to water table and to bedrock, sand susceptibility to flooding.
Liquid limit and plasticity index indicates the effect of water on the strength and consistence of soil material. As the moisture content of a clayey soil is increased from a dry state, the material changes from a semisolid to a plastic state. If the moisture content is further increased, the material changes from a plastic to a liquid state. The plastic limit is the moisture content at which the soil material passes from a semisolid to a plastic state. The liquid limit is the moisture content at which the material changes from a plastic to a liquid state. The plasticity index is the numerical difference between the liquid limit and the plastic limit. It indicates the range of moisture content within which a soil material is plastic.