About ten years ago Dr. R. W. Lorenz of our Department made a study of 150 plantations growing on prairie soil in Illinois. Thirty-six were walnut which ranged in age from 22 to 75 years. The one thing we had the most trouble with was determining their ages. One day we stopped at a farm and talked to a farmer, and we asked him when the trees were planted. This man said he could tell us the exact day. "I was a young lad and a neighbor drove by and said, 'Yesterday Abe Lincoln was shot.'" So we had the historical records to determine the age of that particular plantation.
These plantations ranged in number of trees per acre from 46 to 330. The number of trees per acre has a direct influence on the size or diameter growth of the timber tree. An eight by eight spacing, or 680 trees per acre, eventually will be thinned to 200 trees per acre. That gives each tree proper spacing for best height and diameter growth.
The trees ranged in height from about 31 feet to 85, averaging about a foot and a quarter in height each year. The average diameters ranged from about 12 inches to 15 inches. Individual trees, however, ranged up to 24 inches at breast height (4-1/2' above ground level). Each plantation had had very little or no care. If some of them had been cared for, or "managed", their owners would have had a better wood crop—higher quality and higher quantity too.
Now, as to the growth in the managed plantations. We believe it is possible to grow 300 board feet per acre per year. Compared with upland oak, walnut exceeded it in almost all growth factors up to 70 years of age and then they were about the same.
Of the cultural practices, the most important is probably pruning. Sawing off the limbs growing on the trunk makes all wood produced thereafter free of knots. When the trees reach about six inches in diameter, one should select those he is going to call "crop trees"—about 200 of these per acre—and spend his time getting them to timber size and quality. The other trees are removed over a period of several years, so that you finally have only the 200 high quality crop trees left. The reason I suggest starting the pruning when the trees are six inches in diameter, is that that is the size of the veneer core left after the veneer manufacturer has turned the log for the thin sheet of furniture veneer. Remove the limbs and improve the quality so you get a 16-foot log free of limbs and knots. That is what the buyer is looking for.
I know practically nothing about growing trees for a nut crop, but we seem to have something in common in growing trees both for nuts and timber. Just a lot of it is "horse sense", with a few rules of thumb based upon scientific principles. You must give the crop trees space, give them plenty of room to grow. In the woods they start to grow in a dense undergrowth. The young trees soon reach a height where they begin to dominate their neighbors. There you pick the straight, thrifty-growing trees for crop trees and favor them in your thinning and pruning operations. Tree density influences diameter growth of the trees. In thick stands, trees are usually small and spindly. So plant a large number to give the crop trees good form, then thin the plantation carefully to make it grow.
Grazing and fire are very harmful to tree plantations. Most of the plantations we studied were grazed. A good many were burned. I don't think nut growers would periodically burn their stands to improve the nut production. It is the same with growing a crop of wood. Once the livestock begin to trample or compact the soil, tree growth slows down and when that happens it makes the tree more susceptible to attack by insects and fungi.
As to marketing trees, let's assume you have some material you want to sell. The one thing you want to know is, "how much is it worth?" That is like me asking you what my house is worth. I understand there are persons here not only from Illinois and Iowa, but from New York, West Virginia, Ohio, and Kentucky. Prices on wood products vary not only from state to state but also within a state as well. The things you ought to know are the sizes and the grades of the timber that you want to sell, since they determine price. Now, there are publically employed foresters available to help you. They know your local conditions. The manufacturer's markets determine what he can afford to pay you.
For example, we organized some walnut marketing pools in Illinois during the war. I suppose a half million board feet of Illinois walnut was sold for gun stock material. One company was buying most of the product of the pools. Later we found that this company had a market for low grade stump veneer. Most of the other companies would mark a half dozen trees for their stumps. This company would buy 35 to 40 stumps. Every buyer looked at the same quality and quantity of material, since the trees were all marked. In this case, however, the difference in markets determined the price the manufacturer could pay.
Another thing that concerns price is what we call "logging chance" or how easy is it for the buyer to harvest those trees. I imagine anyone buying trees in Pennsylvania would have considerably more difficulty in getting them out than he would in Illinois. The differences in equipment and methods used to harvest the trees all have a bearing on the price paid the timber owner.