A TECHNIQUE FOR INTRODUCING RADIOACTIVE PHOSPHORUS
INTO THE GRAIN OF GROWING CORN
H. G. M. JACOBSON
Received March 6, 1948
Corn grain containing a relatively high concentration of radioactive
phosphorus was needed for a poultry feeding investigation by the Poultry
Husbandry Department at the University of Connecticut at Storrs. A
gravel nutriculture procedure was decided upon for growing the corn.
Uniformity of maturity was desired so a hybrid field corn (Connecticut
520) was selected as the corn to be grown for this experiment.
Methods
PHYSICAL EQUIPMENT.-Two water-tight boxes having a surface area of
eight square feet and a depth of eight inches were filled with gravel to
within two inches of the tops of the boxes. The gravel was obtained locally
from the C horizon of a Manchester soil. It contained a high percentage
of gravel-sized sandstone fragments mixed with some granitic material.
After sieving the gravel through a half-inch mesh screen, it was washed
over a screen having six meshes per inch. The material going through the
six mesh screen was discarded. Each box was filled to a depth of six
inches with the screened gravel. The boxes were tilted toward one corner
so that they could be thoroughly drained by means of a syphon. Each box
required 42 liters of solution to submerge the six inches of gravel. The
nutrient solution for each box was stored in separate twelve gallon covered
carboys. This solution (table I) was forced once daily with an air pump
from the carboys to the culture boxes and immediately returned to the
carboy by a syphon. The solutions were maintained at a definite volume
by the addition of tap water at intervals when necessary.
PROCEDURE.-On February 1, 1947 three rows of corn were planted 2
inches apart in the row in each culture box. The rows were spaced about
TABLE I
NUTRIENT SOLUTION. The chemical composition of the nutrient solution made up to
42 liters was as shown. Minor elements were added to the nutrient solution as follows:
Ferric chloride, 1.875 grams; Boric acid, 0.125 grams; Copper sulphate, 0.125 gramis;
Potassium permanganate, 0.190 grams.
COMPOUND
TOTAL
WEIGHT
48
...
KNO3 .
Ca(NO,)2 4H,O .46
Ca(H2PO)2 H2O .42
25
MgSO4,
7H,O
...........................
Total grams .161
ppm
WEIGHT OF ELEMENTS (grams)
P
K
CA
MG
S
6.7
5.4
0.0
0.0
0.0
0.0
10.5
0.0
0.0
7.8
6.7
0.0
12.1
288
10.5
250
18.6
0.0
0.0
0.0
18.6
443
0.0
0.0
0.0
2.5
2.5
60
0.0
0.0
0.0
3.2
3.2
76
N
14.5
345
636
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BRIEF PAPERS
637
12 inches apart. The plants were later thinned to 5 plants per row spaced
about 7 inches apart per plant. The corn was illuminated before sunrise
and after sunset to simulate a July length of day. Two fluorescent lighting
fixtures each having two fluorescent day-light bulbs four feet long were used
for this purpose. Insects were controlled by naphthalene vapor at weekly
intervals. A small blower was used at tasselling time to insure proper
pollination. The nutrient solution was tested bi-weekly and the necessary
chemicals were added to maintain a balance of the elements.
The corn started to tassel April 15 and the first silk appeared April
25. On May 9 the kernels were in the milk stage and by June 10 when
harvested they were well matured. The height of the corn stalks averaged
nine feet at maturity. Approximately 10 pounds of good quality grain
were harvested from the two culture boxes (about 390 bu. per A).
RADIOACTIVE PHOSPHORUS INTRODUCTION.-The nutrient solutions were
replaced with tap water May 5 and 166.25 milicuries of radioactive phosphorus in the form of KH,PO4 were added to the water of each culture
solution. The con-centration of KHIPO4 was equivalent to 38.0 gms. of
KH2PO4 and gave a concentration of 189 ppm of phosphorus and 260 ppm
of potassium to the solution. On May 7 full-rate nitrogen and potassium
was added to the nutrient solutions. One-half rate Ca(H2P04)2 1120 was
added May 15 and another one-half rate May 27. No more chemicals were
added for the duration of the growing period.
Results
The harvested corn showed a strong radioactivity in all parts with the
grain being the mnost active of all. On June 13, 100 mg. of the ground corn
averaged 2800 counts per minute. On June 16 calcium phytate isolated
from the corn averaged 47,040-counts per minute for a 100 mg. sample,
indicating an excellent concentration of radioactivity in the phytin phosphorus fraction, as reported to the author by Dr. E. P. Singsen, Acting
Head of the Poultry Husbandry Department of the University of Connecticut, for whom the corn was grown.
SUMMARY.-Employing a gravel nutriculture procedure, corn of high
quality and yield was produced. Radioactive phosphorus was introduced
into the nutrient solution when the corn was in the early milk stage of
kernel production. The mature corn grain had the highest radioactivity
of any part of the corn plant. The radioactive grain contained a sufficient amount of radioactivity so that it proved satisfactory in a poultry
feeding experiment.
The radioactive phosphorus was obtained from Oak Ridge through the
assistance of Dr. E. C. Pollard of Yale University who also assisted in its
preparation for safe handling.
SOILS DEPARTMENT
CONNECTICUT AGRICULTURAL EXPERIMENT STATION
NEW HAVEN, CONNECTICUT
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