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 th.3 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 



