SUB-SURFACE DRAINAGE AND IRRIGATION STUDIES ON EVERGLADES SOILS
D. S. Harrison
Why should we mole our land? How effective is moling? Does the practice
of running moles 30 inches below the ground surface improve our drainage or
irrigation rates? How fast does our water table drop after rains?
Extensive tests on two test plots have been conducted during the past two
years, in an attempt to answer some if not all of the above questions. Two
adjacent 10-acre blocks were used for the field studies. One block was sprigged
with St. Augustinegrass while the other was left fallow. The St. Augustinegrass
block was divided into 5 sub-divisions or treatments, as follows: (1) moled
every 10-ft., (2) non-moled, (3) moled every 15 ft., (4) non-moled and (5) moled
every 20 ft. The fallow 10-acre block was divided into five treatments, as stated
above, except that the non-moled plots were subsoiled on a 24-inch horizontal
spacing. Each treatment or subdivision contained an area of 100 ft x 660 ft.
There were eight peizometer tubes installed in each block and readings were taken
every 5 rows after irrigation and rains and the depth to the water table in each
block recorded.
Results
There was no significant difference in rate of downward movement of soil
water or water table, in the moled plots over the non-moled plots. Also, sub-
soiling on 24" centers 30 inches deep did not increase rate of drop or recession
in water table.
Table 1 lists the water table recession rates for the given treatments:
Table 1. Rate of Recession of Water Table (inches/ hr.)
Hours After Drainage Commenced
aches Rainfall Sod Cover 10 Hours 20 Hours 30 Hours 40 Hours
2.98 0.34 0.30 0.24 o.60
2.54 0.49 0.26 -
2.40 0.43 0.26 -
1.50 0.36 0.32 -
0.37 0.22 -
Inches Rainfall Fallow 10 Hours 20 Hours 30 Hours 40 Hours
2.49 0.47 0.28
1.86 0.30 0.29
1.50 0.41 0.31 -
0.37 0.23 -
When the rate of downward movement of soil water, or water, or water table
drop is recorded for each treatment, the results are tabulated in Table 2.
May 6, 1959
Everglades Station Mimeo Report 59-27
-2-
Table 2. Average rate of Recession in Water Table
per hour), during periods of Drainage:
for each Treatment (in inches
Rainfall (in.)
2.98
2.55
2.40
1.50
1.03
0.37
Non-moled
0.31
0.29
0.32
0.34
0.32
0.15
10 ft. moles
0.31
0.26
0.32
0.32
0.27
0.16
15 ft. moles
0.30
0,28
0.35
0.32
0.16
20 ft. moles
0.32
0.28
0.33
0.35
0.32
0.16
EES 59-27
250 copies
Belle Glade, Florida
|