Experimental Procedure
The three varieties used in the experiment are Meiling, Nanking, and an unnamed variety carried under the accession number 7916. The last variety is characterized by dwarf, heavy-bearing trees that mature their crops very early in the fall, whereas Meiling and Nanking are vigorous, fast-growing varieties that mature their nuts in midseason. In the early spring of 1948 thirty-six two-year-old grafted trees were planted 25 feet apart in the orchard in four short rows of nine trees each. The three treatments consisted of (1) no pruning; (2) pruning to a 2-foot head; and (3) pruning to a 4-foot head. Three trees, one of each variety, were included in a plot or treatment. Thus, the experiment was arranged in a randomized block design with the three treatments randomized in each row and the four rows serving as replications. Each spring the trees received a liberal application of a 10-6-5 fertilizer. Strips six to eight feet wide on each side of the contoured rows received frequent cultivation each growing season, while strips of orchard grass sod were left between the rows to prevent erosion. The soil is Riverdale (tentative series) sandy loam that had been in orchard grass sod for ten years before the experiment was begun. It has been necessary to spray the trees each year with DDT, parathion, or both to control Japanese beetles and mites.
Pruning of the trees was begun during the first winter following the planting in the orchard, but only a few of the lower limbs were removed in order not to dwarf the pruned trees severely. The second winter a few more lower limbs were removed and at this time the two-foot-head treatments were complete. A third pruning was necessary before the heads of the trees in treatment three could be raised to four feet. Detailed records and measurements were made of the diameter of each tree trunk one foot above the ground, and of the weight and number of nuts produced (yield).