28 BULLETIN 462, U. S. DEPARTMENT OF AGRICULTURE. 
The cost per acre of a system for the irrigation of potatoes is 
exceedingly low. This is worthy of notice, as the average cost of 
irrigation in Florida for many of the systems is very high. An 
allowance of $300 as the cost of a well to water 40 acres would 
mean an expenditure of only $7.50 per acre. The field ditches are 
cheaply constructed, and part of their cost may be charged properly 
to drainage. The cost of operation and maintenance is practically 
nothing for an average-sized field, as the farmer can care for the 
irrigation while engaged in other duties. 
The most serious disadvantage of this system is the waste of land 
due to the open ditches in the field. These ditches, which are a con- 
tinual nuisance in cultivating the field, also harbor weeds. It is 
doubtful, however, if it would be a profitable investment to tile the 
lands and do away with the ditches, although some tiling is being 
installed. First cost is an important item to most farmers, and the 
waste of a little land is not a very serious matter in this section 
where land is cheap and uncleared land abundant. 
OVERHEAD-SPRAY SYSTEMS. 
Overhead pipes, bearing nozzles or upright pipe with revolving 
heads, are used extensively in the State. It has been estimated that 
3,000 acres are irrigated in Florida by some form of overhead spray. 
The spray irrigation plants probably are more widely scattered 
over the State than those of any other type. There are plants in 
Gadsden County, in the northern section of the State, and others of 
all sizes and descriptions in nearly all the intervening counties down 
to the southern part of Dade County, on the southernmost tip of the 
peninsula. 
Several localities are supplied with a considerable number of spray- 
irrigation systems, the largest area being in Polk County around 
Barstow and Fort Meade. There is also an important spray-irriga- 
tion center in Sumter County around Bushnell and Webster, and in 
Levy County around "Williston. Several other sections likewise are 
represented, a considerable area being on the lower east coast around 
Miami. Some of these plants will be described in detail and an at- 
tempt made to present the important problems in each case. 
The most common tj^pe of overhead-irrigation system is of com- 
paratively recent invention. It will be called the overhead-pipe sys- 
tem in this bulletin. In this system water is distributed (PI. IV, 
fig. 1) by forcing it under pressure through small brass nozzles, 
which are set 3 to 4 feet apart in carefully aligned elevated pipe. 
The pipe bearing the nozzles is laid 6 to 7 feet above the ground on 
posts set in straight lines about 15 to 20 feet apart. The overhead 
pipe is so constructed that it may be rolled in bearings by means of 
