IRRIGATION IN" FLORIDA. 51 



Figures 7 and 9 both show that before irrigation the soil was very 

 dry all the way down, the moisture content averaging a little more 

 than 2 per cent. In this condition this soil appears perfectly dry and 

 could be used in an hourglass. When the moisture content reads 

 4 to 5 per cent the soil will hold together well when compressed in 

 the hand, and when it contains about 10 per cent the soil is moist 

 enough to pat to a smooth, shiny surface. At about 15 to 20 per cent 

 water can be squeezed out. The above description will give a good 

 idea of the state of the soil when any point of the curve is read. 



Another point brought out by these tests and shown in the charts, 

 is the distance the water will run down furrows. Tests made with 

 different heads of water show that this distance is dependent on the 

 head of water, provided there is some down grade to the furrows. 

 For instance, if small heads of water were used it was found im- 

 possible to run water more than 100 feet in the grove at Maitland. 

 Heads of 25 gallons per minute, considered large for California fur- 

 rows, were useless in the sandy soils. Running the water for long 

 periods did no appreciable good, as the water disappeared downward 

 faster than it could be supplied ; but when the heads were increased 

 it was found that the length of furrow could be increased and that a 

 head of about 120 gallons per minute would run a total distance of 

 650 feet. 



The loose, sandy soils are peculiarly adapted for holding water on 

 the surface for a considerable time when they are very dry. It is 

 then possible to run good heads of water 600 to 700 feet. This could 

 not be accomplished if the topsoil were moist, but as the soils usually 

 are dry when irrigated the other condition need not be considered. 

 The soils of many of the groves near Orlando and some near Tampa 

 and Manatee were found to be much less porous than those of the 

 grove at Maitland. In several of these cases small heads of water 

 could be run long distances. Experiments in a grove at Orlando 

 showed that heads of 25 gallons per minute were adequate for ideal 

 furrow-irrigation methods. 



It would appear from the above that if a grove is located on very 

 sandy soils and it is desired to irrigate by furrow methods, the main 

 concern should be to design the plant so as to supply these heads. 

 This subject will be discussed in connection with actual construction 

 of plants which have fulfilled such requirements. 



EXPERIMENTS WITH LOW-PRESSURE PIPE SYSTEMS. 



The term " low-pressure " pipe is used in this case to designate 

 pipe that will not stand high internal pressure. Ordinary cement 

 pipe and terra-cotta sewer pipe come under this head. Steel, cast- 

 iron, and wrought-iron pipe will withstand high pressure without 

 bursting. 



