Agricultural Science Digest
Vol. 8, March - April, 1966	PURDUE UNIVERSITY
FOLIAGEOMETER DEVELOPED
TO MEASURE PASTURE YIELDS

A foliageometer has been developed by
Purdue agronomy research workers. This
instrument measures the yield of a pasture
field in its natural growing condition.
Nuclear radiation is used to determine
forage yield. The scientists measure the
difference between the amount of radiation
that reaches their detector before and after
the instrument is placed in the vegetation.

The foliageometer is a circular frame
supported by 13 legs. Twelve of these legs
are mounted symmetrically around the outside
edge of the frame and each contains radioac-
tive material (Sr-90). The 13th leg is mount-
ed in the center of the frame. It is the detect-
ing element containing five Geiger-Mueller
detector tubes stacked end to end.

To test the instrument scientists simu-
lated forage by using wooden dowel rods in-
serted in a masonite peg board. They found
that a relationship existed between the amount
of radioactivity passing through the simulated
forage and the amount of radioactivity in open
air . And, the difference can be computed
mathematically. They also found that moisture
affected the readings but that this difference
is proportional to the percent moisture and is
therefore predictable.

Journal Articles 2492 and 2604, G. O.
Mott, R. F. Barnes, C. L. Rhykerd, I. D.
Teare and J. R. Eaton, Agronomy Depart-
ment.
. . .
SOYBEAN YIELD RESEARCH

Why don't soybeans respond to fertili-
zers? Agronomists can prescribe treatments
which will double or triple the yield of corn
on low-yielding fields -- but soybeans do not
respond to similar treatment.
Purdue agronomists have worked with
plant samples, soil samples and other data
from 13 pairs of soybean fields. One of each
pair was from the winning field in Indiana 5-
acre soybean contests and from other high
producing fields . The other member of each
pair was a neighboring farm with the same
climatic and soil conditions but where very
high yields had not been the case.

The scientists found that three elements;
barium, copper and zinc, were the only min-
erals showing increased involvement in the
high yielding fields . Of these, barium is not
clearly understood because it is not consider-
ed an essential element in soybean production.

Data collected clearly indicate that
plant analysis is a powerful tool which can be
used to help reveal why soybeans do not re-
spond to fertilizer treatments . In soybean
production, the final payoff is in the yield of
grain per acre. To know how to increase the
yield, agronomists need to understand what
happens during each of the growth periods of
the plant. Plant analysis can help scientists
gain this understanding. Further research is
being conducted in this area.

Journal Article 2731, R. D. Frazier, .
H. G. Small and A. J. Ohlrogge, Agronomy
Department.

AGRICULTURAL EXPERIMENT STATION
COOPERATIVE EXTENSION SERVICE