COLE ET AL.: TENSION LYSIMETER STUDIES OF ION AND \IOISTURE MOVEMENT
323
Table 1—The influence of soil type on the vertical movement of N, P, K, Ca, Cs'®* and Sb!25 through the soil profile.
Lysimeter areas 5, 6, and 7.
Depth of
plates
Inches
Precipttation
Inches”
Precipitation collected as
leachate,
Elements
Nitrogen
°
me./Uter
Phosphorus
tb./acre
mg./I{ter
Area 5, Cordia, Pisonia coral soil,
1-1/4*
12,0
83
6
17
12,0
12.¢
36
45
3f
18*
30
li,u
11,0
11,0
98
48
14
1/2*
6*
28*
25,35
25, 35
25. 35
69
67
35
* Average of two plates,
58.8
126.1
6,6
121,6
183.5
13
$1.6
112.5
O5
Area 6, Recent deposit coral safl,
Ib,/acre
1,76
1,23
0.71
mg./liter
Calclum
{b,/acre
myg./liter
Cesium!3?
tb,/acre
Antimony !25
count/min./sample
count/min,/sample
Rongelap Atoll, Marshall Islands (Aug, 21 - Sept. 18, 1958)
16.1
40,0
90,1
P43
194.3
380
2.8
50.5
T,6
176.1
270.6
O6
73.8
$1, 0
2015
2477
Rongelap Atoll, Marshall Islands (Aug, 22 - Sept, 18, 1938)
O.33
2.04
0.10
0.54
0,63.
0, 14
0.29
0.15
OLT
Area 7. Glacial till sofl (Everett gravelly
0.46
0.34
0.37
Potassium
0,041
0, 023
0,031
v7
590
890
12
0,18
0,33
1.31
26,05
63.35
0.17
0.85
1.92
37, 30
44,75
0,09
5.80
2.92
81.40
40,50
sandy toam), Fern Lake, Washington (Jan, - July, 1959)
abe
**
“*
68
Ly
14
0.15
0.08
0. 06
-7
-
-7
0.87
0.42
0,28
2.40
1,67
0.37
2,25
1.97
1,82
8.05
2,25
3,35
** Not detectable,
1,
Table 2—The influence of fertilization on the leaching of N, P, K, Ca, and Cs13* through the surface humus horizon (1):inch depth). Lysimeter area 4, Middle Island coral soil.
Preeipt-
tation,
inches
Precipl-
Elements
tation col-
lected as
Jeachate, %v
Nitrogen
Jb, /acre
Phosphorus
% of control value
lb. /acre
% of control value
oe
Potassium
lb, /acre
% af control value
Calcium
lb./acre
% of control value
Cesium!"
count/min,/
sample
% of contro] value
Control -- no fertilizer additions
12.6
73
14,8
100
o.8
12.6
99
19.9
134
2.8
12.6
76
196.1
N addition
1.9
100
6,3
350
205, 0
125
27,8
potassium KC]
200 Ib, /acre of nitrogen as (NH,},SO,
Lysimeter area 6, Recent deposit coral soil.—This soil has
vet to develop a profile except for a cemented layer at 48
inches. The only vegetation, except for scattered Guettarda
and Scaevola bushes, is a surface crust of algae. The pH ranges
from 8.9 at the surface to 9.2 at 30 inches. Other than the
small cation-exchange capacity of the surface algae, there are
essentially no exchange sites in the profile.
Lysimeter area 7, Everett gravelly sandy loam.—tThe soil
of this area is very infertile (Douglas-fir site class low V).
A dense stand of 30-year-old
Douglas-fir is
the dominant
vegetative cover. The pH through the soil profile remains about
5.3, while the cation-exchange capacity decreases from 11.8
me. per 100 g. at the surface to 4.6 at 24 inches.
Fertilization areas.—Three lysimeter areas were established
in the coral soil of Rongelap to study the influence of fertilization on ion movement through a J1%-inch surface A»
horizon. Two separate treatments together with an unfertilized
control were established at each of the three areas. Nitrogen
and potassium were added at the rate of 200 pounds per acre
as (NH,):SO, and KCl.
RESULTS AND DISCUSSION
Soil Type and Soil Depth
The interrelationship between soil type, soil depth and
the volume and ion content of gravitational water is presented in table 1.
The percentage of precipitation reaching the lower
horizons of the soil profiles is markedly decreased by
evaporation and utilization by the plant communities.
Due to differences in interception by the overstory canopy, differences were found between leachate volumes
from plates located at similar depths. At lysimeter area
6, essentially barren of any overstory vegetation, nearly
all of the precipitation was accounted for at the 3-inch
depth. At lysimeter area 7, interception by the dense
canopy of young Douglas-fir removed about 30° of the
precipitation.
The movement of nitrogen decreased with soil depth
in the areas examined. In the basic soils of Rongelap
Atoll, with its hot climate, nitrogen was predominantly
leached as the nitrate, while in the acid soils of Fern
Lake, with its cool climate, the leachates were chiefly in
the ammonium form. The relatively large amounts of
nitrogen in the Jeachates from the Cordia, Pisonia soil
88.8
100
53
K addition
100
185.4
209
210
441
444.0
500
320
100
‘
400
600
(lysimeter area 5), were largely due to droppings from
nesting birds.
Calcium readily leached through all the soils examined, especially the coral soils of Rongelap, since the soil
skeleton in this area is mainly calcium and magnesium
carbonate. The leaching of calcium was further enhanced
at lysimeter area 5 because of a lower pH caused by
leaf litter and bird droppings. The calcium concentration
in leachate from the glacial till (lysimeter area 7) remained nearly constant with depth though the total
amount decreased, indicating some clay adsorption and
plant utilization.
Potassium passed rapidly through the coral soil, the
prevalence of soluble calcium and magnesium carbonates
apparently giving it little opportunity to remain on the
exchange. However, leaching of potassium in the glacial
till (lysimeter area 7) was limited by the adsorption and
fixation on the clay particles in the soil.
In both the glacial till and coral atoll soils only a small
amount of phosphorus moved through the profile, although the addition to the surface (as either litter or
bird droppings) was often considerable. This restricted
leaching was probably caused by a calcium phosphate
precipitation in the coral soil and an iron or aluminum
phosphate precipitation in the glacial till soil.
Leachates from the Rongelap soils were analyzed also
for gamma-emitting radionuclides originating from radioactive fallout in March 1954 (6). Rut6-Rh106, Sb125,
Cs137, Cel44-Prl44, and Eul55 were detected. However,
reliable quantitative estimates could be made only for
Cs!37 and Sb!*5. It is interesting that Cs!87 and Sb!?5 were
present in leachates collected at depths where thesoil
contained no measurable radioactivity above background.
The patterns of leaching of potassium and Cs!9” were
closely parallel (tables 1 and 2). The Cordia, Pisonia
soil (lysimeter area 5), with a surface horizon high in
organic matter, allowed passage of cesium. In contrast
the “recent deposit” soil (lysimeter area 6), virtually
free of organic matter, passed antimony but stopped
cesium, Total radioactivity in the two soils was 11,000
and 13,000 disintegrations per min. per g., respectively, of
which more than 75% was in the top 1 inch ofsoil.