BUREAU OF GEOLOGY


 The organic soils of the Everglades are a collection of organic particles
and mineral particles which are interspersed with void spaces or pores.
When these pores are filled with water the micro-organisms which
actively decompose the organic soil are unable to function or function at
a greatly reduced rate (Snyder, et al., 1978). This is the condition that
allowed organic soils to accumulate before modification of natural drain-
age patterns. Biochemical oxidation of organic soils is facilitated by
warm temperatures, low water tables, high pH and high organic content
(Stephens, 1974).
 Drained organic soils of the Florida Everglades Agricultural Area sub-
side at an average rate of approximately one inch/year (Stephens, 1974).
This rate varies with variation of depth to the water table. Rates of
subsidence for experimental plots with water table depths of 12 inches,
24 inches and 36 inches were measured to be 0.6 inches per year, 1.4
inches per year and 2.3 inches per year, respectively.
 Subsidence has been documented in the Everglades using repeated
surveys of ground elevation along certain lines. In Figures 17, 18 and 19
(Stephens and Johnson, 1951), the solid lines represent the original
elevation of the surface of the ground and the elevation as measured in
1940. The dashed lines indicate the topographic elevations predicted
from subsidence rates. Stephens (1974) notes that subsidence was
measured to be 33.5 inches between 1941 and 1966 in the upper Ever-
glades which may be compared to a predicted subsidence loss of 33.0
inches in 25 years (Stephens and Johnson, 1951).
 Rates of subsidence in the Everglades Agricultural Area vary with the
depth to which the water table is maintained. The depth at which the
water table is maintained depends on optimum conditions for each land
use. Snyder, et al. (1978) note that most vegetable crops produce high
yields when the water table is maintained at 24 inches below the sur-
face. Sugar cane normally requires a water table depth which is greater
than 24 inches; and in certain organic soils, a water table depth of 30 to
36 inches greatly improves sugar cane quality. Water tables for cattle
and sod production may be maintained at levels which would be consid-
ered too high for most crops. It is important to note that extremely high
water tables may cause problems specifically related to crop land use
even though high water tables allow maximum soil preservation (Snyder,
et al., 1978).

 Conservation Measures

 Researchers who have worked in the Everglades Agricultural Area sug-
gest that maintenance of high water tables is the most effective measure
available for conservation of organic soils. Tate (1980) notes that the
only feasible means of controlling subsidence is knowledgeable manipu-
lation of the water table. Snyder, et al. (1978) recommend: "For best
conservation organic soils should be kept flooded whenever not in use.
When soils are used, the water table should be maintained as high as is