928 
Journal of Agricultural Research voi. xxm, No.» 
of vegetative branches. It so happened that no irrigation was required 
until July when the treatments began. Copious winter rains and cold 
spring weather may possibly explain why water was not needed earlier. 
Previous experiments have demonstrated that the most desirable and 
productive type of plant is one which utilizes to the fullest extent in 
fruiting development the space apportioned to it, without injury to its 
neighbors. Such plants have no vegetative branches, or only one or two, 
depending on spacing. To grow plants of this type it is necessary to ob¬ 
serve precautions in thinning and avoid any unnecessary irrigation when 
the plants are young and easily forced into undesirable vegetative 
growth. When precautions are not taken the plants may develop several 
vegetative branches and become so crowded that only a late crop can be 
produced. 
It is essential that the present experiment should not be confused with 
others that have been published, that dealt with the early development 
and control of the branching habits of the plants. 5 The treatment cotton 
receives before fruiting begins undoubtedly is reflected in all of the sub¬ 
sequent behavior of the plants and is a factor in determining the water 
requirements during the fruiting period. The objects and conditions of 
experiments in the spring differ from those of the summer; hence the 
treatments are distinct problems. 
CLIMATIC CONDITIONS 
As the weather during the cotton-growing season is an important 
factor in judging the results of experimental data, a summary of the 
records is given. 
The season of 1920, though unusual in many respects, was more 
favorable for a reliable consideration of several cultural features than 
could be had in a normal year. Lack of heavy summer rains made the 
irrigation problems more definite, and an unusually cool spring assisted 
materially in controlling the early growth of the plants. On the other 
hand, the maximum air temperatures in July were unusually high, 
providing a test of the effects of hot weather. 
Table I gives the monthly average maximum and minimum tempera¬ 
tures from March to October, inclusive, for the years 1910 to 1919, the 
10-year average for each month, and the monthly averages for 1920. In 
comparing the average monthly maximum and minimum temperatures 
for 1920 with the averages for the corresponding month in the preceding 
years it will be seen that those for 1920 generally are lower, and, with the 
exception of the July maxima, are all below the 10-year average. 
The first killing frost occurred on November 29, but there had been 
light frosts, which did little damage, as early as October 14. For a 
period of 10 consecutive years prior to 1920 the average date of the first 
killing frost at Sacaton is November 17. 
The summer rains, which usually occur in the latter part of July and 
the early part of August and are a complicating factor in the problem 
of irrigation of cotton, were almost negligible in the season of 1920, as 
shown in Table II. This precipitation has not been considered, since 
the showers were so slight and so widely separated that the plants were 
not affected, but the data are presented in Table III. 
• Cook, O. F. a new system of cotton culture and its application. U. S. Dept. Agr. Farmers’ 
Bui. 601, 12 p., 2 fig. X914. 
- single-stalk cotton culture. U. S. Dept. Agr. Bur. Plant Indus. Crop Acclim. and Adapt. 
Inves. B. P. I. Doc. 1130, 11 p., ia fig. 1914. 
