The fertilizing of nut trees, however, offers more difficulties than do the annual crops. Experiments on this subject have been few and the information obtainable is rather meagre. Consequently, a few years ago, the Office of Soil Fertility Investigation, which is conducting fertilizer investigations on a large number of the annual crops grown on the prominent soil types or soil regions of the United States, started, in co-operation with the Office of Horticultural Investigations of the Bureau of Plant Industry, a number of fertilizer experiments on pecan orchards, involving a study of several soil types suitable for nut production and attempting to ascertain the proper fertilizer requirements for the pecan on these soils. While these experiments have been running only five years, which in point of time is very small in the life of a pecan tree, yet the different fertilizers employed already show some highly interesting results, sufficient to indicate that certain fertilizer applications undoubtedly influence the growth of the tree, its productiveness, and quality of the nut produced.
The experimental fertilizer mixtures are all prepared here in Washington in a fertilizer-mixing plant on the department's Arlington Farm, on the Virginia side of the river. The fertilizer house is well stocked with all of the various fertilizer substances used in agriculture, ready for mixing; nitrate of soda from Chili, potash from France and Germany, and our own far western states; cottonseed meal from the South, tankage and dried blood from the slaughter houses of Chicago and Omaha, Tennessee or Florida phosphates, and acid phosphate, ammonium sulfate from the coke ovens of Pennsylvania, Thomas slag from England, in short, all sorts of commercial materials from near and remote sources, for study and use in fertilizers.
(Slides were then shown of the exterior and interior of the plant where literally thousands of experimental fertilizer mixtures are prepared to study the requirements of the various soils and crops, and are then shipped in freight cars to the various experiment places. Two slides showing the application of fertilizer in a large orchard where tractors are employed in carrying on the various cultural operations and also in a small orchard where hand labor is employed, were also shown).
The scheme of fertilizer experimentation adopted in this work is rather complete and so planned as to include fertilizers carrying the principal fertilizer constituents, phosphate, ammonia and potash, singly, in combinations of two elements, and in combinations of three elements, in various proportions in a regularly graded manner. The following scheme illustrates these mixtures of different analyses, the first figure denoting the percentage of phosphate, the second the percentage of ammonia, and the third the percentage of potash in the fertilizer. The various mixtures are numbered consecutively.
1
—-
20-0-0
2 3
—- —-
16-0-4 16-4-0
4 5 6
—- —- —-
12-0-8 12-4-4 12-8-0
7 8 9 10
—- —- —- —-
8-0-12 8-4-8 8-8-4 8-12-0
11 12 13 14 15
—- —- —- —- —-
4-0-16 4-4-12 4-8-8 4-12-4 4-16-0
16 17 18 19 20 21
—- —- —- —- —- —-
0-0-20 0-4-16 0-8-12 0-12-8 0-16-4 0-20-0
It is quite apparent that in this scheme the entire field of fertilizer formulas is covered in a regular way. In addition to this formula plan other experiments are also under way to determine the influence of the different fertilizing materials, carrying the phosphate, ammonia and potash, and the influence of lime, rock phosphate, various green manuring crops, etc. The experiments are carried out in commercial orchards on several soil types and in several localities.
While the years the experiments have been running are yet too few for any final conclusions, and the details too numerous to present in a brief sketch here, there have nevertheless been some very interesting results from the use of fertilizers which is readily shown by a few lantern slides. Here is, for instance, a view of a fertilized and an unfertilized section of one of our experiments in Georgia. The views were obtained in the fall, and one could tell at a glance, not only that the unfertilized trees were not as large, but also quite strikingly that they had nearly lost all of their foliage, whereas the trees on the fertilized section were still in full foliage, thus presenting a very strong contrast. The effect of fertilizers on the foliage is shown also in a series of slides of representative trees, from one of our experiments in Louisiana, likewise taken in the fall. The first tree had not been fertilized, the second had been fertilized with phosphate and the third with potash. The one fertilized with phosphate appeared slightly larger, but it can again be observed that all three trees were, at the time the picture was taken, nearly three-fourths defoliated. The next two trees from the same experiment, fertilized respectively with a nitrogenous fertilizer and with a complete fertilizer, and photographed at the same time, show the influence of these fertilizers strikingly in that they are still in complete foliage, as well as showing a more vigorous growth. Three slides of fertilized and unfertilized trees from still different experiments all show the fuller foliage and better branching of the fertilized trees, especially those fertilized with the nitrogenous fertilizers or the complete fertilizers.
The yields of these trees cannot here be taken up but, in general, these fertilized trees came into bearing earlier and have yielded double and treble the number of nuts produced by the unfertilized trees.
(In conclusion, there was shown a slide of the yield of nuts from an experimental tract of a commercial orchard of about 20 acres, in which the yield from a fertilized acre was compared with the yield from an unfertilized acre. It was noted that the unfertilized acre gave a yield of approximately two barrels, whereas the fertilized acre gave an increase of two bushel baskets more than the unfertilized.)
Dr. W. E. Safford, Botanist, Bureau of Plant Industry, then spoke on the
Use of Nuts by the Aboriginal Americans.