IRRIGATION in FLORIDA. 17 
ence in moisture content between the cultivated and noncultivated 
grove, that cultivation has done little good, as it is quite probable 
that the trees within the cultivated space have had the benefit of the 
moisture conserved by cultivation, which was lost through grass roots 
or evaporation in the uncultivated grove. Observation of the effects 
of cultivation shows that it will prevent wilt for some time after 
uncultivated groves are showing distress both in loss of fruit and 
by curling leaves. On the other hand, the moisture curves show 
conclusively that both cultivated and noncultivated groves have de- 
pleted their available moisture supply from the soil, which evidently 
can be supplied only by rain or irrigation. A great number of tests 
have proved this point beyond dispute, yet there are many growers 
in Florida who advocate that cultivation will take the place of 
irrigation. Scientific tests show that this can not be true in case 
of protracted drought, although it may be true for short periods of 
dry weather. In any case, it appears that it would pay to cultivate 
the groves during the dry weather if all possible moisture is to be 
conserved. 
OTHER FACTORS DETERMINING THE NEED OF IRRIGATION. 
The two factors treated above, rainfall and soil, doubtless are of 
primary importance in determining the need of irrigation in the 
State, yet there are a number of other factors that enter into the 
matter. Shallow-rooted crops, such as truck or small fruits, will 
suffer from drought much sooner than deep-rooted crops, such as 
orchards. The difference in the cropping also calls for a different 
type of irrigation system, as it is evident that the shallow -rooted 
crops, upon light soil subject to rapid drying, demand a system that 
will apply water rapidly and more often than is necessary for 
groves. The difference would be much more evident were it not for 
the fact that most of the vegetable crops are grown on low grounds 
which are not so subject to harm in dry weather. 
The average field crops of Florida, as a rule, are not irrigated. 
There are two reasons for this: first, that most of the field crops 
either are grown in the northern counties where the rainfall is more 
evenly distributed, or in the southern counties after the truck crops 
are off, which usually is well toward the rainy season; and, second, 
that most of the field crops stand considerable drought and at the 
same time do not require such intensive cultivation as the truck 
crops or citrus fruits. The profits per acre usually are small com- 
pared with truck crops or citrus groves, and under ordinary condi- 
tions will not warrant an outlay for irrigation purposes. 
Irrigation is used in some cases to prevent frost from injuring 
plants ; in some citrus groves to combat insect pests. These problems 
will be treated later. 
61867°— Bull. 462—17 3 
