Table 2 contains the average yield per acre. This follows the same pattern
 as millable tonnage. Here again no definite reason can be given for these appar-
 ently irratic results.

 Table 3 contains the average pounds of.sucrose per ton of cane. The maximum
 difference was between variety Fi 31-962 grown at 33.6 inches with overhead ir-
 rigation and variety Co. 281 grown at a 14.4-inch water table. This difference
 was 66 pounds sucrose per ton of cane.

 The higher yield from the 14.4-inch depth does not.seem to have any logical
 explanation. A more logical response would seem to be an increase in yield as
 the depth to water table increases. There would be a point at which the depth
 to water table would become too great for the plant to secure enough water for
 growth and the tonnage would decline as the depth to water table increased below
 this point. The response in the above test did not conform in this way.

 The organic soils of the Everglades release stored nitrogen to plants through
 the action of microorganisms. A higher sucrose content could partly be explained
 for the cane growing at the 14.4-inch depth as the plant would have had a restrict-
 ed area in which to secure nutrients and it is known that a lower nitrogen content
 as the plant approaches maturity usually will produce a higher sucrose content.
 It also follows that, if the above were true, the amount of millable cane pro-
 duced under such conditions might be less. This again is not true in this study.

 Another possibility which might help to explain partially the above response
is the amount of carbon dioxide present in the organic soils of the Everglades.
Decaying organic material produces carbon dioxide. It has been shown that organic
soils oxidize at a more rapid rate as the water table is lowered. All roots are
killed by high carbon dioxide concentrations, but many appear to tolerate 9 to 10
percent for short periods. Carbon dioxide measurements made on these plots show-
ed carbon dioxide content to be approximately 10 percent 21.5 inches belcu the
surface on the 24-inch water table.

 Again, this report is intended to call attention to the problems encountered
when attempting water control studies under field conditions. The need for repli-
cated trials is evident.












EES 66-11
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