Mar. 24,1923 
Summer Irrigation of Pima Cotton 
943 
little, if any, loss, as bees and wasps were numerous in the fields at all 
times and pollination was usually accomplished soon after a flower 
opened. Injurious insects were noticeably absent and none of the shed 
bolls were found to be damaged. 
INDICATION OF OVERWATERING 
It became apparent about August 18 that the plants in the “ heavy ” 
border in series I were in distress. Growth had practically stopped, and 
the rate of flowering showed a distinct decline. Many of the lower leaves 
were dying and dropping off, and the other leaves had an unnatural 
yellowish green color. This usually would be taken as a sign of urgent 
need of water, but since the soil was obviously wet, even on the surface, 
that explanation would not serve. This border was not irrigated with 
the other “heavy” borders on August 23. No indication of a similar 
condition could be found in the “heavy” borders in series II and III, 
although up to this time they had received the same irrigation treatment. 
In view of the fact that no similar behavior was found on the adjacent 
borders or elsewhere on the station, it seems probable that excess moisture 
was causing the distress in border C1-5, because of some peculiarity of the 
soil in series I, which resulted in a lower water requirement. A comparison 
between the number of irrigations on the “normal” border in series I and 
the “normal” borders in series II and III shows that series I required only 
half as many irrigations. Thus the same effects as the irrigation of the 
“heavy” border in series I every 10 days might have been obtained in the 
“heavy” borders of series II and III by irrigation at 5-day intervals. 
The affected border was irrigated on September 3, as the plants showed 
wilting in the forenoon although the ground still appeared moist. A 
crippled, or partially destroyed root system may possibly have been 
responsible for this wilting, which ceased after more water was given. 
On September 8 it was noted that the plants had improved in color and 
later that the color had continued to improve so that only a slight 
difference could be detected. 
However, the setback this border had received was very noticeable 
and its recovery was too late to make good the handicap it had received, 
as can be seen from the plant growth data (fig. 2) and the picking record 
(Table IX). 
YIELD 
The record of seed cotton picked from each border is shown in Table 
IX, which also gives the number of plants per row and the number with 
vegetative branches. Four pickings were made, and the cotton from each 
row was weighed and recorded separately so as to allow an accurate 
evaluation of differences. 
From Table IX it can be seen that the total seed cotton from the 
“normal” border in series I was 340.6 pounds, from the “medium- 
heavy” border 392.7 pounds, and from the “heavy” border 280.4 
pounds. In series II tie “normal” border yielded 267.5 pounds, the 
“medium-heavy” border 274.9 pounds, and the “heavy” border 265.9 
pounds. From series III, the “normal” border totaled 254.3 pounds, 
the “medium-heavy” border 294.6 pounds, and the “heavy” border 
302.2 pounds. 
As shown in the foregoing data, the yields of seed cotton from the 
differently treated border varied to a considerable extent, but with no 
consistence in regard to treatment. The greater fertility of the soil is 
27976—23 - 2 
