948 
Journal of Agricultural Research 
Vol. XXVIII, No. 9 
Table X.— Showing the varietal differences in length of boll development period 
of 6 varieties of cotton grown under conditions obtaining at the United States 
Field Station, Sacaton, Ariz., in 1923 
Mean number of days from flower to open boll 
5-day periods (flower dates) 
I 
i Hartsville 
! 
Durango 
Pima 
Acala 
Mebane 
Lone Star 
June 27 to July 2. 
48. 5±0. 71 
53. 3± . 47 
51. 5± . 19 
50.8± . 20 
53.1± . 23 
52. 7± . 17 
54.8± . 41 
57. 4± . 45 
59. 2±1.18 
61. Oil. 91 
63. Odb . 00 
69. Q± . 68 , 
_i 
47. 0±0. 29 
47. 4± .27 
46. 4=t . 44 
44.8± . 45 
45. 7± . 22 
44. 8d= . 22 
45. 5± . 28 
47. 7dfc . 33 
47. 4± . 58 
52. Oi . 80 
53.0i .82 
48.1±0. 30 
50. 9± . 58 
48. 5± . 18 
47.9± . 52 
48. 5± . 20 
50. 4± .31 
50. 7±1. 09 
51. 5± . 33 
56. 6± . 79 
60. 8rbl. 66 
48.3±0. 32 
50. 2± . 67 
48. 6± . 22 
48. 2± . 39 
50. 3± . 30 
49. 6± . 33 
49. 5± . 77 
54. 4±1.12 
54. 4±1.09 
59. 0± . 00 
47.3±0. 80 
49. 5=b . 71 
49. 2± . 16 
47. 7± . 26 
50. 3± . 24 
51. 8db . 22 
52. 0± . 00 
54. 2± . 47 
58.1±1. 42 
July 3 to July 7.. 
45. 7±0. 66 
49. 7± . 47 
53. 6± . 22 
54. 7=fc . 24 
57. 0± . 24 
57. 5± . 21 
60. 8d= .25 
64. 6=fc . 25 
68. 3± . 33 
72. 6db . 45 
79. 7± . 69 
83. 3± . 41 
85. 5db . 01 
90. 7± . 86 
July 8 to July 12_.. 
July 13 to July 17__ 
July 18 to July 22__. 
July 23 to July 27____ 
July 28 to Aug. 1... 
Aug. 2 to Aug. 6_ 
Aug. 7 to Aug. 11.__ 
Aug. 12 to Aug. 16.. 
Aug. 17 to Aug. 21.. 
Aug. 22 to Aug. 26.... 
Aug. 27 to Aug. 31.. 
75. 5dt . 79 
74.8±1. 32 
79. 0± . 00 
Sept. 1 to Sept. 5__ 
71. 3±2. 46 
. 1 . 
Sept. 6 to Sept. 10__ 
j ' 
1 
1 
i 
"1. 
THE PERIODS OF BOLL DEVELOPMENT 
Table X shows the mean number of days from flower to open boll of flowers 
produced from June 27 to August 31, grouped in five-day periods. It will be 
noted that in all varieties except Pima the boll development period was shorter 
for flowers that opened between July 13 and July 17, than for the periods imme¬ 
diately preceding and immediately following. This undoubtedly was due to the 
fact that the plants suffered from lack of moisture for a few days about September 
1 to 4, causing some of the bolls to open prematurely. The Pima plants did not 
suffer, and the bolls did not show the reduced period of development. 
Another decline in the boll development period, which also is probably due 
to a period of water shortage, is noticeable in the Hartsville, Durango, and 
Mebane varieties in bolls produced from flowers that opened between July 23 
and July 27. If this interpretation is correct, such recording of the periods of 
boll development would be of use in cultural experiments in determining the 
conditions of growth, and whether sufficient irrigation water had been applied. 
The gradual lengthening of the boll development period as the season advances 
is in agreement with the results reported by King ( 3 ), Martin and Loomis (7), 
and Martin, Ballard, and Simpson ( 6 ). The mean period of boll development 
of the six varieties for the season of 1923 are shown in Table X. 
COMPARISONS OF YIELDS 
The cotton growers in the Salt River Valley are confronted with the problem 
of choosing the variety that will yield the largest returns under their conditions. 
In order to meet the higher fixed charges of irrigated farming and the higher 
cost of harvesting the cotton crop in this region, a larger return per acre must 
be assured than is necessary in the greater part of the cotton belt. The returns 
per acre derived from Pima cotton during the years 1916 to 1919, when it was 
the only variety grown, were undoubtedly greater than could have been secured 
from any other variety. In recent years, however, the market conditions have 
favored the Upland varieties, though opinion is much divided as to which Upland 
variety is the best for their purposes. Though the question turns largely upon 
the yields in the present state of the market it is recognized that premiums 
can be secured for Upland staples of good quality, and that it is desirable to 
unite upon a single Upland variety in order to develop local supplies of good seed. 
