938 
Journal of Agricultural Research 
Vol. XXVIII, No. 9 
The experiments were planted in adjacent blocks of seven rows of each variety, 
the same field being used each year, though the varieties were not kept in the 
same order. By referring to Table X the plats on which a particular variety 
was planted in each year can be ascertained. 
The plantings were made as soon as danger of frost was past with a two-row 
planter adjusted for rows 44 inches apart. Seeding was at the rate of about 35 
pounds of seed per acre. This is a somewhat higher rate than is generally used 
by commercial growers, but it has been found that this amount is required to 
insure a uniform stand which is necessary in experimental plantings. The 
date when the varieties were planted each year is given in Table I. 
The height of the seedling plants when thinned varied somewhat in different 
years, but usually they averaged about 12 inches high, and were in no case 
allowed to grow over 15 inches in height before thinning. In all four years the 
plants were thinned as nearly as possible to one foot apart in the rows, which 
is the spacing most used by Pima cotton growers in Arizona. Thinning was 
never completed earlier than May 28 nor later than June 13. 
Table I .—Dates of 'planting variety tests at Sacaton , Ariz. 
Variety 
1920 
1921 
1922 
1923 
Pima....... 
Apr. 2 
_do_ 
Apr. 9 s 
...do_! 
Mar. 27 
Apr. 18 
Do. 
Lone Star....... 
“May 10 
Mar. 27 
Durango... .. .. 
_do_ 
...do_ 1 
Do. 
Acala..... 
...do_ 
: Apr. 8 
Do. 
Mebane__.......■_ 
Do. 
Harts ville__-___ 
Do. 
a In 1922 Lone Star was first planted on Mar. 27 but poor germination and cold weather killed many 
of the young plants and further affected the stand, which necessitated the entire replanting of this plat 
on May 10. 
Indications of water stress in Pima plants are easily recognized, and the 
irrigation problem is not very difficult after one becomes familiar with the 
characteristics of the plants. In the early stages of development, the irrigation 
water was applied at such intervals as was necessary to keep the plants from 
wilting, except during short periods in the middle of the day, and to prevent the 
upper fruiting branches from projecting above the terminal buds of the central 
stalk, which is an indication that growth is being checked. After flowering 
commenced the time of irrigation was governed largely by the position of the 
flowers. An effort was made to keep the flowers from appearing at the tops of 
the plants, except during the fall months when upward growth of the plants 
had practically ceased. 
Plant behavior which indicates the proper time for irrigating the Upland 
varieties is much more difficult to recognize than with Pima. The flowers are 
hidden more by the leaves and do not appear at the tops of the plants until the 
cotton has been in distress for several days from lack of water. General wilting 
of Upland plants at any time of day during the summer months is usually an 
indication that water has been withheld too long. 
The dates when water was applied to the different varieties in 1922 and 1923 
are shown in Table II. Days on which more than 1 inch of rain fell are also 
included, as such rains were considered as the equivalent of an irrigation. These 
data are given for 1922 and 1923 only, as no detailed notes were taken in the 
previous years on flowering, shedding, and plant growth, in connection with 
which irrigation dates might be of interest. 
