BUREAU OF GEOLOGY


possible for that use". Stephens (1974) lits a number of suggestions
geared toward conservation of organic soil: "(1) provide adequate water
control facilities for keeping water tables as high as crop and field
requirements will tolerate; (2) make productive use of drained lands as
soon as possible; and (3) intensify research studies to develop practices
to prolong the life of the soils".
 It has been suggested that extending the life of organic soils by plow-
ing under cover crops or litter (Snyder, et al., 1978; Stephens, 1974) is
probably not an effective conservation measure. The rate at which peat
forms is extremely slow and the volume of plant litter produced is very
small. Snyder, et al. (1978) discuss an example which clarifies this rela-
tionship. Sugar cane produces an amount of top growth exceeded by
few, if any, plants. An average cane crop (30 tons/acre) is estimated to
contain approximately eight tons of dry matter. If all of the dry matter
from an entire crop were added to the soil, it could be assumed that
about half of it would be decomposed rapidly. One acre-inch of top soil is
about the amount lost to subsidence each year in the Everglades Agricul-
tural Area. That amount of soil weighs approximately 50 tons. Thus, four
tons are replaced each year, which is still only approximately 1/12 the
amount which is lost.



 The Near Future of the Everglades Agricultural Area


 Snyder, et al. (1978) have included a discussion of land use in the
Everglades Agricultural Area through the year 2000. It is noted that the
predictions of Stephens (1951) have proved reliable (compare Figures 20
and 21). These predictions are presented in Table 2 (Snyder, et al.,
1978). Although land elevations are shown through the year 2000, sub-
sidence will continue. By the year 2000, only approximately 80,000
acres of soil three feet in depth or deeper will remain. It is predicted that
sugar cane acreage will decrease, pasture acreage will increase signifi-
cantly and vegetable acreage will remain essentially unchanged assum-
ing the economic viability of such operations. By the year 2000, over
500,000 acres will be less than three feet in thickness. Approximately
half of this will be less than a foot in depth (Snyder, et al., 1978). The
depth of three feet is significant because, at depths of less than three
feet, the use of mole drains becomes impractical. The soils which have
subsided to depths of less than one foot face an uncertain fate. Snyder,
et al. (1978) suggest that while some of those soils may be suitable for
pasture, the soils may be abandoned for agricultural uses. It is also sug-
gested that the remaining soils and the existing water-control structures
be used to produce aquatic crops. The authors suggest that such a usage
could greatly extend the useful agricultural life of the soils.