CONSERVATION (Part 3 of 5)

How Soil Conservation Works

Groups interested in improving farming practices have been around for many years. But the federal government did not get involved in soil conservation until the early 1930s.

Problems that occurred during the 1930s, such as the Dust Bowl, caused people to recognize the need for government leadership in the areas of soil conservation and farming.

• Agricultural acts passed by lawmakers in 1929 and 1932 provided money to be used for erosion research.
• In 1933, during the Great Depression, Congress passed a bill that would allow people without jobs to work in erosion control for the government. In this way, soil conservation could be put into practice and the unemployed would have work.
• The Soil Erosion Service, later renamed the Soil Conservation Service, was created in 1935 as a result of this bill and has been responsible for managing conservation programs.

In 1933 the Soil Erosion Service (soon renamed the Soil Conservation Service) was created as a major division of the United States Department of Agriculture. The Soil Conservation Service has devised a land classification system that offers guidance in the proper use of land. Such factors as slope, type of soil, amount of rainfall, humidity, and vegetation type are considered when determining land use for maximum productivity. Of the eight government-designated land classifications, classes I, II, III, and IV may be used for cultivated crops; however, classes III and IV require skilful management to avoid serious erosion. Classes V through VII can be used for forests and for grazing. Class VIII land, which includes sandy shores and extremely rocky places, is considered suitable only for wildlife or for scenic and recreational purposes.

Covering the ground with plants is one of the key elements in soil conservation. To prove this, the Department of Agriculture experimented with two steep plots of adjacent land one planted with crops and the other thickly covered with grass. The cultivated plot lost 7 inches (18 centimetres) of topsoil in 11 years. By contrast, it was estimated that it would take 34,000 years to lose the same amount of topsoil from the grass-covered plot.

Plant cover tends to hold rainwater where it falls and thus prevents the soil from blowing or washing away. Gullies can be healed in many cases by planting new plants. They provide a tangle of leaves and stems that trap and hold in place part of the soil carried by run-off Another way to heal gullies is to build brush dams across them at regular intervals.

Then soil and water running down the gully are caught behind the dams and held in place.

To help prevent the start of erosion, farmers may use a variety of conservation measures:

Contouring. This practice involves ploughing, planting, and cultivating sloping fields around hillsides, with curving furrows horizontal to the hill, instead of furrows running straight uphill and downhill. The curved furrows catch rainfall and allow much of it to soak into the ground. They also catch soil washing down from higher levels.

Strip-cropping. Strips of close-growing plants, such as grasses or clover, are alternated between strips of clean-tilled row crops, such as corn and soy beans The strips of close-growing plants hold water and keep it from eroding the cultivated strip below. These strips are planted on the contour.

Terrace, in geology, stretch of elevated, level land along banks of a river, lake, or ocean; frequently occur in series, one rising above the other; artificial terraces are used effectively in landscape gardening and in agriculture to hold moisture and prevent erosion.

Terracing. On long slopes a low ridge, or terrace, thrown along the outer side of the slope catches soil and rainwater and retards run-off Encouraging plant growth on a terrace will help hold soil.

Listing. In dry regions a Lister plough can be used to throw a ridge of dirt to each side, creating a trough about 18 inches (46 centimetres) wide and 7 inches deep. Crops are planted in the bottom of the trough.

Shelter belts On treeless plains, belts of trees planted at the edges of fields break the force of winds across the fields and reduce wind erosion.

Deep tillage (also called stubble mulching, or primary tillage), method of ploughing to conserve the land.

Deep tillage, stubble mulching. Instead of turning over the soil with a mouldboard plough, a deep-tillage plough breaks the soil below the surface. It leaves the surface vegetation or harvest remains from the previous crop to act as a cover.

Different crops need different substances, called nutrients, to enable them to grow.

Crops get these needed nutrients from the soil. If the same crop is grown in the same field every year, the soil will soon lose nutrients needed by that crop.

Crop rotation is the practice of planting different crops in a field each year or every few years.

With careful planning, crops can be rotated in a way that builds up nutrients in the soil for the next crop. Here's an example:

Many crops need nitrogen to grow, and they take it from the soil. Other plants, like legumes, take nitrogen out of the air and put it back into the soil. By rotating legumes with other crops, the nitrogen in the soil can be replaced.

Crop rotation. Planting different crops each year on a piece of land keeps the soil productive. One crop can benefit the next. For example, nitrogen is essential for plant growth and is added to the soil by legumes, such as clover, alfalfa, soy beans, and cow peas These combine nitrogen from the air with other elements and store it in the soil through their roots. In a year or two the plants can be ploughed under. This is called green manuring.

After the roots have rotted, other plants that need nitrogen but cannot use nitrogen in the air for example, corn and potatoes can use the stored nitrogen for growth. Rotations are programmed with strip-cropping by shifting the close-growing strips and the tilled strips at fixed intervals.

Water can be polluted by many things. One of these is the topsoil or silt that washes into streams and rivers. This silt washes into streams and rivers from land that has been badly managed.

When silt washes into streams and rivers, two harmful things may happen.

1) Silt that floats in the water limits the amount of air in the water. Fish need air to breathe. When silt limits the air in the water, the fish die.

2) As the movement of water slows down, silt drops to the bottom of the stream beds

There are ways of controlling erosion of silt from land into streams and reservoirs. Conservationists try to make sure that the right steps are taken to prevent the silting of streams.

Cover crops. Land is kept covered in winter and summer with either a growing crop or the residue, such as corn stalks, from the crop previously grown. When cover crops are ploughed under for green manuring, the plant foods added to the soil improve its water-holding capacity and increase its fertility.

Fertilization. Chemical or natural fertilizers replace the soil substances used up by crops.

Erosion on Urban Land

Crop land is not the only soil subject to erosion. The land on which housing and other urban projects are built is particularly susceptible because its protective cover is generally removed.

Mulch, material such as manure, leaves, pulverized earth, placed on surface of soil to retain moisture and to protect plant roots from frost.

To prevent erosion on construction sites, builders should take corrective action. For example, mulches placed on steeply excavated slopes usually prevent soil from washing or blowing away. Straw or fibre netting may be used as mulches. On sites where erosion control is more difficult, hydro seeding can be used. Grass seed, fertilizer, and mulch are power-sprayed on excavated slopes. The quick-growing grass then stabilizes the soil against erosion.

WILDLIFE CONSERVATION

The preservation of wildlife greatly depends upon water and soil conservation. All native plants and animals constitute the wildlife of a region and are a product of the land resources and habitat conditions. But, like humans, wild animals must have food, water, and shelter. Destroying the forests, marshes, ponds, and grasslands destroys their food and water supplies and the places in which they live.

1872: Yellowstone National Park. Although the concept of national parks was first suggested in 1832 by American artist George Catlin, it was not until March 1, 1872, that the first national park in the United States was established by Congress. Yellowstone Park was the beginning of a large system of 49 parks that today can be found in nearly all parts of the country. These parks, as well as other monuments, are managed by the National Park Service.

Once Yellowstone was opened, other countries began setting aside nature preserves similar to America's national parks. Canada, for example, established a 10-square-mile area of hot springs at Banff, Alberta, in 1885 as a national park. Today there are national parks on all continents, except Antarctica.

Yellowstone is located in parts of three states: north-western Wyoming, southern Montana, and eastern Idaho; it covers 2,219,823 acres (898,329 hectares). Several sub ranges of the Rocky Mountains are in or around the park's borders: the Snow Mountains, the Gallatin Range, the Absaroka Range, and the Tetons. Several national forests surround Yellowstone. The Grand Canyon of the Yellowstone River is a 19-mile gorge running through the park. Among Yellowstone's other distinctive features are 10,000 hot springs, including 200 geysers, many of which erupt to heights of 100 feet (30 meters). The most famous geyser is Old Faithful, named for the regularity of its eruptions.

The park is heavily forested, and in 1988 a series of disastrous fires destroyed much of its vegetation and animal life.

Of the original native wildlife of the United States many species are now extinct. These include the passenger pigeon, the Carolina parakeet, the great auk, the Labrador duck, the Pallas cormorant, the dusky seaside sparrow, and the heath hen. Mammals gone forever include the Eastern elk, the Plains wolf, the sea mink, and the Bad Lands bighorn. Many smaller birds and mammals have also become extinct in the wild. Populations of the ivory-billed woodpecker and the California condor no longer exist in the wild in the United

States.

The number of moose, caribou, wild sheep and goats, and grizzly and Alaska brown bears grows smaller every year. Much wildlife is now protected by law from over hunting and overfishing. However, if habitat destruction of their natural homes continues, many will be unable to survive.

The United States Fish and Wildlife Service maintains a list of endangered and threatened species of the United States. Environmental concerns for a variety of reptiles, amphibians, small fishes, insects, and molluscs is reflected in the number of species classed as threatened or endangered.

The Endangered Species Act has been effective for preserving some species that seemed destined for extinction. For example, the American alligator had been reduced to a relatively small number by the early 1960s due to illegal hunting for hides and meat. After 20 years of protection, the species recovered to such a large extent in many parts of its range that it led to a relaxation of the laws in the 1980s so that limited hunting was permitted.

Many events can cause a species of animal to become endangered. For example, some animals are killed because people want trophies or desire to wear clothing made from furs and skins.

However, the main reason many creatures have become endangered is because humans are destroying their habitats. Two such habitats are the Florida Everglades and the rain forests of Brazil. Too often, places that are attractive to animals are just as attractive to people, who want to build various facilities.

Unfortunately, nothing can bring back a species that has been lost. Such extinct creatures will only be seen in museums or pictures.

Worldwide, the International Union for Conservation of Nature and Natural Resources keeps track of species threatened with extinction. Endangered species include many of the world's great cats, whales, certain species of rhinoceros, tapirs, and many other mammals, birds, and reptiles. Housing and other facilities needed by an expanding human population are encroaching on their habitats.

Many species are the victims of the illegal pet trade and of the trade in exotic pelts and skins; the increasing availability of guns and poisons is responsible for the extermination of other species. The African elephant, once common throughout the sub-Saharan region of the African continent, has been greatly reduced in numbers due to illegal poaching for the ivory trade.