RADIO-LCGLOG1
Lous
the potassium fertilization, but not enough for dilution to account for the
differences in Cs-137 contents. The absence of radiocesium in the P-K treatment
was associated with an unusually high K level in the plant tissue.
Following this preliminary experiment with tomato, a further greenhouse trial
was made with squash, variety Hubbard. Squash was used because it is one of
the few herbaceous plants successfully cultivated in the northern Marshall Islands.
The treatments were set up in triplicate, replication was good, and the plants
grew well except for some chlorosis which was not entirely corrected by the
application of 1.5 mg Fe per pot as NaFeEDTA(Fe chelated by ethylenediaminetetraacetic acid). The plants were divided into upper leaf, lower leaf, and stem
fractions at harvest. Since the results were qualitatively the same for the different
fractions and spaceis limited, Table 1 presents the yields and K and Cs analyses
on the basis of the entire shoot. The results of this experiment were in general
TABLE 1
CesiuM anD Potassium CONTENTS OF SQUASH AND OF NATIVE SPECIES
Description
Average
dryyield
(gm)
meq
kK
per {00 gm
Squash in greenhouse pot cultures (total shoot)
No fertilizer
4.5
29.6
N3 Py Ko?
8.0
17.7
N; P, Ky
7.4
36.3
No Py Ky
N3 Po Ka
Ny, Py Ke Fe
5.5
8.4
10.2
47.5
26.8
26.3
C37
d/m/g!
210434
WOo+1!
B0+414
150414
120+16
220415
Foliage coltected from woody plants on Rongelap Island
Messerschmidia argentca
upper leaves
33
240+8
(soil pit 25)
Scaevola sericea
(soil pit 25)
Pandanustectorius
(village-2)
lower leaves
upper leaves
lower leaves
upper leaves
lower leaves
6.6
35
12
18.5
8.9
15047
110+6
150 +7
263-45
13544
lError given is 95% counting error.
*Subscripts refer to rate of application per acre of N, P:O;, or K.0,
in hundreds of pounds.
similar to those with the tomato, although there was no response in yield to
potassium additions, and the tissue from the NoPiK2 treatment contained Cs-187.
In all cases the fertilizer amendments caused a sharp reduction in the Cs-137
content expressed on a d/m/gm dry basis, although this effect could not be
associated with a particular fertilizer element. The depressive effect of fertilization on cesium uptake is also evident when the total Cs-137 in the shoot is calcu-
lated, indicating that dilution by a greater amount of dry yield cannot explain
the reduced cesium content. In the different portions of the squash shoots, Cs-137
was in all treatments highest in the upper leaves, lowest in the lower leaves,
and intermediate in the stem. Squash plants grown on the same benchat the
same time but in a greenhouse loam soil contained no Cs-137. Results of analyses
for Ca, Mg Na, and PO,in thetissue do not offer any obvious explanation for the
differences in cesium uptake, although it should be noted that calcium levels