Forestry Quarterly 13: 25-30 (1915)
CHARCOAL AS A MEANS OF SOLVING SOME NURSERY PROBLEMS
GEORGE A. RETAN

In an article, "Effective Fertilizers in Nurseries," (FORESTRY QUARTERLY, Vol. XII, No. 1), mention was made of an experiment in the use of charcoal in the Mont Alto Nursery at the Pennsylvania State Forest Academy. This work was started by Forester T. O. Bietsch in 1912. At that time the charcoal used was obtained from old pits in the mountains. This charcoal was thought to have a comparatively large percentage of wood ash as one of its constitutents, and this uncertain composition made it doubtful as to whether the action of the charcoal in the bed was purely physical, or partly chemical. The beds where this charcoal was used were so much better than the other beds in the nursery that it seemed worth while to determine just what the effect of pure charcoal might be, and to compare the beds so treated with untreated beds, and with beds treated with pit charcoal.

The soil in the nursery at Mont Alto is a heavy clay, quite unfavorable to the raising of coniferous seedlings. The nursery has never produced as many seedlings as its capacity, judged from area alone, would call for. In very favorable years there has been a good production, and in other years there has been comparative failure. The problem confronting the man in charge of the nursery has been that of conquering this unfavorable soil condition. Many different methods had been tried without success, and the marked benefit of the charcoal at once aroused hopes that a successful method had been found. Pit charcoal was hard to obtain, and rather expensive; but if pure charcoal would answer the same purpose, it could be obtained at very little cost from the remains of the old charcoal pile used by the furnace in the days of the Mont Alto Iron Company.

During the past season there have been carried on a series of experiments for the purpose of answering these questions in connection with the use of charcoal. About 130 beds were treated with pure charcoal from the furnace pile. The beds, which were treated in 1912 and had produced one crop of two-year seedlings, were spaded up and again sown. In addition, some of the beds made were in the sections as yet untreated and were of pure clay. All of these beds were managed in the same manner throughout the season. A few of the clay beds received applications of acid phosphate. On ten of the clay beds different combinations of fertilizers were applied two weeks before the seed was sown, a combination to each bed. In this way it was hoped to get comparisons of charcoal and commercial fertilizer effects in the same section.

The seed used on all these beds was purchased by the Department of Forestry from Otto Katzenstein & Company, Atlanta, Georgia. It was sold as seed gathered from open-grown trees in New York, and stored in cloth bags in a room with a temperature of 90° to 100° Fahrenheit. It was, as a result, very dry. This seed, like all the other seed used in the nursery, was tested by Mr. Barnes, a senior at the Academy, in connection with his thesis and under the direction of the writer. The methods used were adapted from those described in an article in the Proceedings of the Society of American Foresters (Vol. VIII, No. 2), "The Technique of Seed Testing." Boxes 7 inches wide, 5 inches deep, and 28 inches long were filled with sterile sand, and the sand pressed down so that exactly 1/4 inch of sand could be put over the seeds. In each compartment 500 seeds were carefully distributed over the area. The sand was well wetted before sowing, and each compartment received 125 cubic centimeters of water every other day. The temperature of the germinating room was allowed to fluctuate between 65° and 85° Fahrenheit. The room was heated by steam, lighted from the north, and well ventilated.

The "germinative force" was taken as the percentage of germination attained when the germination in a single day dropped below two seeds, if in the following day the germination did not exceed two. The germinative capacity was taken as the germination attained when no seeds germinated in five successive days. The"real value" was taken as a result of the formula

Germinative Force x per cent. of Purity  = Real Value per cent.
————————————————————
100

By "percentage of purity" is meant the ratio of the weight of the seed alone to the weight of the seed and dirt as taken from the bag. This gave a valuable figure for determining the number of ounces which ought to be sown per unit of area. In the White pine seed used in these experiments the germinative force was 51 per cent. (37 days); purity, 83 per cent.; real value, 42.3 per cent.; germinative capacity, 51.7 per cent. (50 days); actual germination on nursery check plot, 40.7 per cent in 70 days; establishment August 1 of 1 ounce seed, 27.7 per cent.

There were 28,000 grains of this seed in a cleaned pound and 24 ounces of the seed were sown on each of the beds used in these experiments. These beds contained either 96 or 100 square feet each, depending on the location. The real value of this amount of seed was 17,766 seeds. It was estimated that the loss during the season would be from 30 to 50 per cent., and that a permanent stand of about 10,000 seedlings to the bed would be left. That this estimate was not far wrong is shown both by the data given below and by the nursery check plot in which the seed showed a germination of 40.7 per cent., and an establishment of 27.7 per cent., or a loss of a little over 30 per cent.

In addition to the beds sown in the spring, on December 13, 1913, nine beds were made up and sown with 2 pounds each of the same seed. As far as known, this is the first fall sowing of White pine ever made in this nursery. The germination in these beds was considerably above the figures given for the tests. Counts of six strips on different beds, each strip 4 inches wide the full width of the bed, showed an establishment of 696 per running foot, 17,000 seedlings to the bed, or 30.3 per cent. Since these beds suffered very severely from birds during the migrating season, the germination must have been, comparatively, very high. This is especially shown in the manner in which they started germination. Instead of the slow, irregular germination of the beds sown in the spring, these beds were characterized by a complete, even germination very early in the season. The sun screens were placed on these beds on May 1. This experiment was so successful that thirty beds have been made up this fall for 1915. If these are equally successful, fall sowing will be adopted for this nursery as far as possible. So far it has been tried only with White pine.

The other beds of the experiment were made up during the period April 22 to 30. Germination in these beds was very slow and irregular. Dry weather in May made it necessary to water the beds before germination. The mulch was not removed until the last week in May, and at that time it was feared the beds would be failures. Careful watering, however, brought the germination up to a satisfactory percentage. On September 21 these beds were estimated on the basis of a count of all the seedlings present on a strip across the bed 1 foot wide, the strip taken at the center of each bed. The thirteen beds with no charcoal content gave an average establishment of 17 per cent. The fifteen beds treated with charcoal in the spring of 1912, which have raised one crop of two-year seedlings, gave an average establishment of 26.8 per cent. A count of fifteen strips on beds of the section containing 97 beds treated in the fall of 1913, gave an average establishment of 28.2 per cent., or 11,850 seedlings to the bed, a better average than the test plots.

It may be fairly objected that the best test in such an experiment is not numbers, but quality of the product. To meet this objection the following table is submitted. One hundred trees were taken from each of four beds; the trees being taken in each case from the northeast corner of the bed, and as they ran. There was no attempt at any selection of best or even average trees. From the standpoint of density, the trees from the untreated bed. had the most growing space, and the trees from the fall beds the least. The table shows, however, that the weights do not correspond to the growing space, but to the kind of soil, and to the age of the tree.

Number
of Lot
When Sown Time of Application
of Charcoal
Weight of the
Bunch in Grams
1 spring 1914 none present 22.0
2 spring 1914 spring 1912 39.3
3 spring 1914 fall 1913 35.3
4 fall 1913 fall 1913 40.3
51 fall 1913 fall 1913 48.5
1Same bundle as previous one hundred, but fair sized trees substituted for the culls. Illustration numbers correspond to this table.

The great problem of the nurseryman is the control of the fungi causing the so-called "damping-off." During the past few years there have been several publications issued telling of work along this line. The work of Spaulding Hartley and Johnson may be mentioned. The preventatives which are given as being effective seem to be too expensive for use in a nursery where the desire is to raise fewer seedlings to the bed, to work for stockiness, in order that the seedling may be fitted for permanent transplanting at the end of two years. It is believed that five to six thousand strong plants taken from 100 square feet ought to be the aim rather than twelve to fifteen thousand for transplanting. Since the first cost of the bed is the same under the two methods, there must be a saving effected in the care of the less dense bed during the two-year period. There seems to be good basis for a belief that the application of charcoal to the bed is a very great aid in the prevention of "damping-off." Certain phases of the subject are not as yet settled and experimentation will have to continue longer before a definite statement to this effect can be made. There were 350 beds sown in the Mont Alto Nursery this year, White pine leading with 250, Norway spruce being sown on 50, and larch, Scotch pine, and Pitch pine occupying a small number each. Constant observation of these beds seems to indicate that where the proportion of charcoal in the bed is large there is less "damping-off." In the section with 97 charcoal beds, only six showed severe loss. The germination in these beds was so delayed that the loss of 30 per cent. during the season was not surprising. When the loss from weeding and other causes is subtracted, not a very large proportion remains to be assigned to the fungi. In another section in which ten beds were made almost wholly of charcoal, there has been no loss at all from "damping-off" and the beds are far too dense. In the clay beds adjoining these, the loss was very great during the period from the twentieth of June, in which rain fell thirteen out of twenty-six days.

No exact percentage can be given as the proportion of charcoal in the beds. The plot was plowed and disk-harrowed; then about 3 inches of charcoal was spread over the top. The paths were shoveled into the beds, raising the beds about 4 inches above the surface. The spading was not done very deeply, thus keeping the charcoal in the upper portion. Contrary to expectation, these beds did not dry out easily, even in the severe drought of the fall, while they drained out rapidly after heavy rains.

There are so many factors affecting the activity of the "damping-off" fungi that it is almost impossible to say that any one remedy will meet all of them. Since the fungi demand optimum conditions of heat and moisture to develop, it would seem that a control of the moisture conditions would be most effective in regulating the trouble, and this is the usual procedure. It is commonly secured through the manipulation of the screens. Besides using the charcoal, two other means of regulating the moisture conditions have been tried. One is the use of sand as a seed cover. A mixture of sand and compost, half and half, proved most effective in preventing a caking of the surface soil, but a larger percentage of sand seemed to help more in damage prevention. However, it cannot be said that pure sand was an absolute preventative, even though it was sterile. In most cases the sand was an aid, but there were conspicuous exceptions, especially on some beds in heavy clay. Another means tried was a change in the method of watering the beds. It was observed that in dry, hot weather, watering, even with the utmost care as to time and amount, increased the liability of attack. A portion of the nursery was so planned that it was made possible to irrigate the paths. The water seeped in very rapidly from the side and supplied the roots of the seedlings without wetting the surface of the bed farther than by the water drawn up by capillarity. This was a very great aid in maintaining favorable conditions at the surface of the bed. Incidentally, it forced out large numbers of the white grubs which are so destructive.

It is too early to give definite answers to the questions raised in the use of commercial fertilizers. By the end of another summer it is expected there will be a large amount of data at hand by which the seedlings of charcoal and fertilized beds can be compared. In the same soils, "damping-off" has been much worse in the fertilizer beds. This is true whether in clay or charcoal beds. Probably the fertilized seedling will have a little advantage in weight, but even that is not certain. The greatest advantage of the charcoal is that the effect is permanent. The fertilizer must be constantly renewed.