IRRIGATION IN FLORIDA. 27 



This section is very similar to the Sanford trucking district, both 

 as to its soil conditions and its water supply. The ground surface in 

 general is very level and the soil is of the flatwoods variety, inter- 

 spersed with patches of low hammock lands. The highest elevation 

 is about 17 feet above sea level, the average being about 10 feet. 

 The potato lands are underlain with an impervious stratum or hard- 

 pan at depths varying from 20 inches to 5 feet. 



The water supply is from flowing artesian wells (PI. Ill, fig. 1), 

 the average depth of which is about 200 feet. Some of the wells give 

 a good flow at 110 feet, while others are nearly 400 feet deep. Most 

 of them are 4 inches in diameter; the diameter of the average San- 

 ford well is 2 inches. A good 4-inch well will supply about 300 

 gallons per minute. The cost of the wells increases with the depth, 

 the average cost being about $200 to $300, or $1.50 to $2 per foot, 

 complete. 



In most cases water is applied to the crops through open field 

 ditches placed in parallel rows 30 to 40 feet apart. (PL III, fig. 2.) 

 These ditches are fed by a main ditch which runs at right angles 

 to them. The dimensions of this vary somewhat, but it usually is 

 about 2 feet on the bottom, 1| to 2 feet deep, and 7 to 10 feet wide 

 on the top. The slope often is gradual enough to accommodate a 

 row of potatoes along the banks. The head ditch in the average farm 

 is a partnership affair running along the road, and is used as a 

 general drainage ditch when necessary. 



The water runs from flowing wells into the main head ditch, from 

 which it is led into the field ditch. The water is controlled from the 

 main to the laterals by simple wooden gates, or, in some cases, by 

 temporary dirt embankments thrown up with a shovel. As at San- 

 ford, the grades are very slight and the head of water often is relied 

 upon to force a flow. The process of irrigation consists of filling the 

 field ditches and keeping them so until the soil between them has 

 become subirrigated. The action is essentially the same as that 

 at Sanford, the open ditches merely taking the place of the under- 

 ground tile. 



The amount of water needed per irrigation by this system and the 

 time required depend upon the amount of moisture in the soil. Gen- 

 erally a 4-inch well flowing 300 gallons per minute will irrigate 40 

 acres. In times of protracted drought the well is run continuously, 

 one well taking care of 40 acres. The need for one 4-inch well on 

 every 40- acre piece is accepted generally. If the flow is 300 gallons 

 per minute, this means a duty of water of 7-J gallons per minute per 

 acre. This is not far from the amount allowed for some of the 

 irrigation systems of the West. The time of irrigation depends upon 

 the rainfall. No irrigation is needed in some years, while in others 

 water is required during a large part of the growing season. 



