Redcedar, if it is used in the outside row, should be spaced 4 to 5 feet apart. Spruce can be spaced 6 feet apart.

All trees in interior rows should be spaced 6 to 8 feet apart in the northern region, 8 to 12 feet apart in the central Plains, and 12 to 15 feet apart in the southern Plains.

Rows should be spaced 12 to 15 feet apart in the northern and central Plains and 16 to 20 feet apart in the southern Plains. Species should be spaced relatively close in the rows to provide compactness and density.

Allowances for root space can best be adjusted by altering the distances between rows.

NURSERY-GROWN PLANTING STOCK is best for dryland shelterbelts. One- or 2-year seedlings one-fourth to three-eighths inch in diameter just above the swelling of the root collar and 16 to 30 inches tall are the best planting stock.

Conifers may be planted as bare-rooted transplants, but the use of potted stock may assure a higher rate of survival. Farmers who want to pot their own trees can buy seedlings from a nursery and put the trees in cans 5 to 6 inches high and 2 to 3 inches in diameter. Pots may be made of light asphalt paper if cans are not available. The small trees should be kept in the pots for a year.

Tree planting in the northern and central Great Plains is best done in April and May. January to March are the best months farther south.

If the trees are received from the nursery in the fall or early spring, they should be heeled in until planting time. If storage is for over winter, a deep trench should be dug that will take all of the roots and part of the tops. The roots and lower parts of the stems are then covered with soil, which is thoroughly packed and watered. Spring heeling in does not require quite so thorough a job, but it should be done so that the roots do not dry out.

Most tree planting in the Plains is done by machines. If machines are not available or it is not practical to use them, one should dig holes large and deep enough to spread out the roots.

The slit method, or planting behind a shovel, may be used when the soil is wet and the trees have few branched roots. Potted evergreens may be planted with a machine if the containers are less than 3 inches in diameter. Larger containers may be planted with post-hole diggers or shovels.

Care should be taken to prevent drying out of roots by wind and sun during the planting operation. The trees should be carried in a pail of water or wrapped in a wet sack.

All trees that fail to grow the first year should be replaced the following spring. Each year's delay makes it more difficult to establish young trees in an older planting because of the increased growth of the older trees and their competition for soil moisture.

Success with shelterbelts depends on the care one gives them. Clean cultivation should be practiced both between rows and between trees in the row as long as it is possible to do so or until the tree shades the soil to an extent that weed growth is negligible. Competitive weed and grass growth must be controlled if trees are to be successful on dryland sites.

Duckfoot, sweep-type, and spring tooth cultivators, which can be attached to a tractor, are suitable for the center area between rows. They leave the soil in good condition to absorb precipitation and to prevent soil blowing. Single disks should not be used because they ridge the soil against the trees and leave the centers low, thus causing heavy runoff on sloping land. Heavy mulches of hay and straw should not be used as a substitute for cultivation. Their use, when necessary, should be confined to control of erosion.

Livestock can damage or ruin windbreaks and shelterbelts. Cattle and sheep particularly pack the soil and make it less receptive to the intake of water. All types of stock browse and damage the limbs of trees and shrubs. They should be excluded from the shelterbelt. A fence, if it is necessary, should be built when the planting is made.

A clean-cultivated strip should be maintained on all sides of every shelterbelt to prevent entrance of fire from the outside. The cultivated strip will also help to prevent the entrance of weeds and sod. It should be maintained for the life span of the shelterbelt.

The use of cover crops should be confined to light, sandy soils that are subject to wind erosion. A few rows of vegetables, corn, or a narrow band of grain planted between the rows of trees will help to control soil blowing. When the tree rows become dense enough to reduce wind velocities, the practice of planting cover crops should be discontinued.

If irrigation of shelterbelts is possible usually it is not tree rows can be planted closer together than the distances recommended for dry sites. The shelterbelt should not be watered for about a month before the first killing frost, when the trees should be hardening off for winter. Irrigation after growth ceases or before the final freeze-up is advisable when the soil is dry.

ADDITIONAL INFORMATION on the planting and care of windbreaks and shelterbelts in the Great Plains may be obtained from the Extension Service of the respective Plains States; the local Soil Conservation District office; the Northern Great Plains Field Station, Mandan, N. Dak.; the Cheyenne Horticultural Field Station, Cheyenne, Wyo.; and the Southern Great Plains Field Station, Woodward, Okla.