Machine-Made Forests

by PAUL O. RUDOLF PLANTING a forest takes a good deal of work. On a few acres, hand labor may make up nine-tenths of the cost. Even on the large public forest projects in the Lake States, where some machinery is used, a third or a half of the cost usually goes into hand labor. Add to that the fact that the season for planting trees is short, and you have the reasons why farmers and foresters are greatly interested in any machines that can do part or most of the planting operation.

Much of the preparation of the ground for planting can be done mechanically. In some places trees are planted without previous preparation of the ground. If there is much growth of sod, weeds, brush, or other trees, however, competition usually is too severe for the young seedlings. In the Lake States and some other regions, competition for the first few years is reduced by skinning off patches of vegetation 1 to 2 feet in diameter (called scalping) or by plowing furrows about 6 feet apart. The latter method has proved cheaper and better and has been used on a million-odd acres in Minnesota, Wisconsin, and Michigan.

Fairly light, horse-drawn sulky plows were used to prepare most of the planting sites in the Lake States before 1930; walking plows were also used to some extent. Then a little heavier type of plow, usually drawn by a 15-20 horsepower wheel tractor, came into use. After the opener areas had been planted, plows had to be developed for use in heavier growth of brush and weed trees. Several heavy, middle-buster plows, usually drawn by 35 horsepower crawler-type tractors, proved quite satisfactory. These plows threw the furrow slice in both directions and opened a furrow at least 18 inches wide. The lighter plows threw the furrow slice in one direction and opened a furrow about 12 inches wide. Furrowing has the advantage of reducing competition by other plants for moisture and soil nutrients, but, by removing the topsoil, furrowing makes it necessary to place the tree roots in a poorer layer of soil.

Disking gives promise of being an effective and useful method of preparing planting sites in the Lake States. Where it has been used on brushy sites, thorough disking has reduced competition effectively and has had the added advantage of working the more' fertile topsoil into the surface layer in which the roots are planted. In about 200 acres of disked plantations on the Chippewa National Forest in Minnesota, 4-year-old red pine transplants 2 years after planting had better survival and height growth than on a comparable area of furrowed plantation.

The best apparatus for disking brushy areas so far developed has been the Athens-type disk plow drawn by a 40 horsepower tractor. The area must be cross-disked; that is, the disk should be pulled over the ground twice, the second time in a direction at right angles to the first trip. It is even better if a third trip in a diagonal direction can be made, although this may make the cost too high. Experience on the Chippewa National Forest indicates that with a skillful operator cross-disking can be done at a cost less than 10 percent above furrowing.

Several machines that prepare the ground and plant in one operation have been developed and used to some extent in the United States. Although they differ in detail, most of the machines contain these features: A coulter to cut the sod and small roots, a plow to turn a furrow, a trencher to open a slit, packing wheels to close the slit, and a container for the planting stock. One or two planters ride the machine and insert the tree roots in the slit just ahead of the packing wheels. Most of the machines are tractor drawn. In the Northeast, two machines, differing chiefly in size, were developed several years ago and have been used fairly extensively. During the later years of Shelterbelt planting in the Plains Region by the Prairie States Forestry Project and the Soil Conservation Service, most planting was done by machines, which, however, were adapted only for planting in ground completely prepared as for farm planting. The Naber tree-planting machine was developed by the Forest Service for planting in the Nebraska sand hills. None of these machines, however, has found acceptance in the Lake States.

Tree-planting machines have been developed by State agencies in Wisconsin, Michigan, and Minnesota with which a crew (tractor driver and one to two planters) can set out 1,200 to 2,000 trees an hour. The Michigan and Minnesota machines are still in the trial stage. The machines developed in Wisconsin, have been used quite extensively since their development in 1943.

Under the leadership of Extension Forester Fred B. Trenk, two types of tree-planting machines were built. One is designed for use by farmers on old fields, principally on sandy soils, and the other is designed for use on cut-over sandy areas where some stumps and brush may occur.

The farm-type tree-planting machine designed by the Wisconsin Agricultural Experiment Station is built around the modern, single-bottom, heavy-duty tractor plow. The standard plow bottom is replaced with a middle-breaker plow, under which is attached a box shoe about 4 inches wide, 8 inches deep, and 3 feet long. On the front of the shoe is a chisel snout that serves the double purpose of holding the shoe in the ground and elevating the soil out of the planting trench instead of merely prying apart a slit in the soil. A rear assembly with press wheels provides a seat for the operator as he places the trees (carried in one or two boxes just ahead of the planter) in the trench shoe. The press wheels pack the soil around the tree roots after a pair of plates flow loose soil into the trench. Trees up to 4 years of age may be planted easily in the 4- by 8-inch trench, but in general 3-year-old stock has been proved most satisfactory except for jack pine, which handles best as 2-year-old stock.

The second model, designed by the Wisconsin Conservation Department, is generally similar to the farm model, but is built around a middle-breaker fire plow. Because of its extremely heavy construction, it will operate in land too stony or stumpy for the lighter farm machine. The ordinary farm tractor will operate the lighter machine, while a moderately heavy crawler type tractor is needed to operate the heavier machine.

The tree-planting machine parts, which cost from $60 to $75 in 1943-45, may be made detachable from each of these two designs, so the plows can be used during the rest of the year for regular farm work.

A three-man crew consists of a tractor driver, a planter, and a stockman. The latter takes care of the stock, loosens and separates the trees for easy planting, and hands them to the planter. The crew can plant up to 16,000 trees in an 8-hour day with either machine. However, the daily production usually runs from 6,500 to 11,000 trees.

The economy of planting with the machines may be illustrated by records obtained in 1944 and 1945 from operations in which four machines, two of each type, planted a million trees on 800 acres in 850 hours of operation. Not counting the cost of the planting stock, which would add up to $5 a thousand trees planted, the work was done at a Cost of about $3.30 a thousand, or $4.65 an acre-only a little more than half the cost with conventional methods of ground preparation and hand planting. Naturally, with higher wages and costs of equipment and materials, the costs of planting will go above those figures.

A tree-planting machine called the Michigan State College reforestator, which combines some of the features of the Wisconsin and Plains Shelterbelt machines, has been developed by T. D. Stevens and L. E. Bell at Michigan State College. Mounted on a standard farm implement "unicarrier" with power lifts, as is the Shelterbelt tree-planting machine, it is otherwise quite similar to the Wisconsin machine. It differs principally in that the plow can be raised up for use on prepared ground and that through the use of the unicarrier it is easy to adjust the plows to varying depths and, by lowering one wheel and raising the other, to do contour planting on slopes up to 30 percent. Although the standard trencher on this machine makes an opening 4 inches wide and 8 inches deep (as does the Wisconsin machine), it is removable and may be replaced with a trencher that will make a larger opening to accommo-date larger planting stock.

The reforestator can be pulled by an ordinary farm tractor, although wheel-type tractors are not satisfactory on loose sands or steep slopes. Because truck wheels are substituted for the standard uni-carrier wheels, the machine is easily transported as a trailing unit behind a tractor or automobile. Reports are that a two-man crew can set out 10,000 trees in an 8-hour day with the reforestator.

The Forestry Division of the Minnesota Conservation Department, under the supervision of Raymond Clement, has developed a machine for planting trees on open sand plains. The machine differs from the Wisconsin and Michigan machines in that it was not developed particularly for farm use, no plow is used, and two planters ride the machine. The ground is broken by the trenching shoe. Fairly extensive trials in 1945 indicated that a 3-man crew, 2 planters and a tractor driver, could plant an average of 1,500 trees an hour.

Of course, planting machines also have some disadvantages: Areas with much rock, stumps, brush, or other cover, or heavy soil cannot be planted; roots over 8 inches long may be looped or improperly placed; and only areas that are comparatively level can be planted. Nevertheless, these tree-planting machines are promising and merit widespread trial to explore their full possibilities. Individual farmers probably could not afford to own a tree-planting machine, but groups or organizations could own machines to be used by their members. In Wisconsin, machines owned by public agencies are rented to farmers.

THE AUTHOR Paul O. Rudolf is a silviculturist at the Lake States Forest Experiment Station, maintained by the Department in cooperation with the University of Minnesota. For the past 15 years Mr. Rudolf has been doing research in forest planting in the Lake States.