NORTHERN GREAT PLAINS FIELD STATION IN 1923 7 
TESTS OF PRUNING, SPACING, AND METHODS OF CULTIVATION 
Twelve belts of the same combination of trees were planted in 
1918. Fom* of these belts are given clean cultivation and no prun- 
ing, but differ in the spacing distances used, as follows: 4 by 4, 4 by 
8, 4 by 12, and 8 by 8 feet. Half of the remaining belts are spaced 
4 by 4 feet and the other half 4 by 8 feet. One belt at each of these 
spacing distances is given clean cultivation and pruned moderately, 
one is given clean cultivation and pruned severely, one is mulched 
and not pruned, and the other is fenced off and neglected. 
At the close of the sixth year of growth all the blocks spaced 4 by 
4 feet show the effects of crowding, but in the blocks spaced 4 by 8 
feet or wider there is no evidence of crowding. In the blocks that 
are given clean cultivation there is no noticeable difference between 
those that are not pruned and those that are moderately pruned. 
The bad effects of severe pruning and also of neglect are evident. 
The mulched blocks compare favorably with those that have received 
clean cultivation. 
Table 6. — Average heights in the fall of 1923 of four kinds of trees, each planted at 
two spacing distances 
Kind of tree 
Year 
planted 
Average height 
Spaced 
4 by 4 feet 
Spaced 
4 by 8 feet 
Green ash 
1918 
1918 
1918 
1921 
6.4 
10.0 
8.2 
6.9 
7.5 
Boxelder.. 
10.9 
Sharpleaf willow 
8.4 
Northwest poplar . . ._ . . . . 
7.5 
Eight 10-row blocks of approximately 260 trees of a single species 
each have been established. In four of these the trees are spaced 
4 by 4 feet and in the other four they are 4 by 8 feet. Four kinds 
of trees were used, each kind filling one of the 4 b}^ 4 and one of the 
4 by 8 blocks. In all cases the trees in the blocks spaced 4 by 8 
feet present the more vigorous appearance. Table 6 gives the 
average height at the end of the growth period in 1923 of the trees 
in each block. 
Table 7. — Average height at the end of the sixth season of the trees in each row of 
two combinations of conifers, each with three spacing distances 
Row 
Average height (feet) 
Combination and 
kind of tree 
Row 
.\verage height (feet) 
Combination and 
kind of tree 
Spaced 
2 by 4 
feet 
Spaced 
4 by 4 
feet 
Spaced 
4 by 8 
feet 
Spaced 
2 by 4 
feet 
Spaced 
4 by 4 
feet 
Spaced 
4 by 8 
feet 
Combination No. 1: 
Scotch pine 
Jack pine 
Bull pine 
Scotch pine 
Jack pine 
Bull pine 
1 i 6.3 
2 . 7.9 
4.8 
7.6 
3.1 
5.9 
7.3 
2.3 
3.7 
7.1 
3.2 
3.8 
8.6 
2.5 
Combination No. 2: 
Black Hills 
1 
2 
3 
4 
5 
3.5 
3.2 
6.4 
4.3 
2.5 
3.7 
2.6 
7.4 
3.7 
3.8 
3.1 
3 
4 
5 
6 
3.2 
5.7 
7.6 
2.5 
Bull pine 
Jack pine 
Scotch pine 
Black Hills 
spruce 
2.3 
6.9 
3.5 
3.3 
