24 
BULLETIN 958, TJ. S. DEPARTMENT OF AGRICULTURE. 
eral use on the soils in question. After the crop had reached matu- 
rity 400 hills of each crop were dug, the tubers counted, and the weight 
for each hill obtained. The results are given in Table X. 
Table X. — Relation of soil type to the number and the weight of tubers as shown in tests of 
tiro varieties of potatoes grown under fidd conditions near Greeley, Colo., in 1918. 
Triumph variety. 
Rural New Yorker variety. 
Character of the soil. 
Number 
of tubers 
per hill. 
Weight of tubers 
(grams). 
Weight of tubers 
Number (grams), 
of tubers 
Per hill. 
Average. 
per hill. 
Per hill. 
Average. 
Heavy clay 
Clay loam 
Fine sandv loam 
3.1 
4.2 
5.9 
194.6 
387.2 
489.4 
62.0 
93.3 
83.3 
3.0 376.7 
4. 9 663. 7 
6. 3 1, 033. 5 - 
125.3 
136.5 
162. 8 
The lowest production of tubers with respect to both number and 
weight per hill was on the heaviest soil, while the highest numbers and 
yields were produced on the lightest soil, indicating a tendency toward 
an increase in the productivity of the plant as the character of the soil 
changes toward the lighter types. Since these results cover only a 
single season, it is possible that the relationships found to exist in 
this experiment might be modified somewhat under different climatic 
conditions as well as by differences in the relative state of produc- 
tivity of the different soil types. The data do, however, show very 
conclusively the influence of the character of the soil on tuber pro- 
duction. 
TIME AND NUMBER OF IRRIGATIONS AS RELATED TO TUBER PRODUCTION. 
The material used for the study of the relation of irrigation methods 
to tuber production consisted in 1917 of one row each of seven varie- 
ties divided into four sections. The first received no irrigation. On 
the second section irrigation was not begun until after tuber forma- 
tion was well started. On the third and fourth sections the first appli- 
cations of water were before tuber formation had started. On the 
fourth section the number of irrigations was somewhat in excess of 
what would be considered the optimum in commercial field practice. 
At the time of harvest 30 hills were dug from each section of each 
row (except in the fourth section of the Early Ohio, where disease re- 
duced the number of healthy hills to 10), and the hills were weighed 
and the tubers counted. 
In 1918 practically the same plan was followed, except that the 
number of varieties was reduced to five, and each section of each 
variety consisted of two full rows of approximately 200 hills each. 
The effects of the early irrigations in this season were to some extent 
counterbalanced by a relatively large rainfall between the periods of 
germination and the beginning of tuber formation. 
