Report on the Agricultural Experiment Stations, 1953 Page: 93
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PLANT DISEASE INVESTIGATIONS 93
tion reaches a critical point. Diameter increased when there was
available moisture and decreased when moisture became unavailable
in the top 1.5 to 3.0 inches of soil.
The possibility of speeding up the growth of loblolly pines by fertilization
was investigated by the North Carolina station in 6-, 9-, 12-,
and 16-year-old plantings located in the Hill Demonstration Forest
in Durham County. Thirteen different fertilizer treatments involving
several rates and combinations of ammonium nitrate, treble superphosphate,
and muriate of potash were applied in replicated plots.
One year after fertilization, a tendency was noted toward greater
height and diameter in trees on the heavier fertilized nitrogen and
phosphate plots, but differences were not significant. Broadcasting
of the fertilizer was apparently as effective as hole placement. Nitrogen
content was higher in needles of trees receiving nitrogen than in
needles of trees receiving only phosphorus and potash fertilizer.
The value of thinning dense stands of young Virginia pine was
shown by the Pennsylvania station. In 1942 an 8-year-old stand containing
3,000 to 3,400 trees was thinned to about 420 crop trees per
acre. Measurements 11 years later showed 240 trees of 5-inch diameter
at breast height in the thinned area as compared with 70 in the
unthinned area. There were, however, sufficient trees of 4 inches or
more in diameter in the unthinned plot to provide enough crop trees
to stock a normal stand at 50 years of age.
The importance of careful site selection for forest tree plantings
was stressed by the New York (Cornell) station. Records taken in
two southern counties showed that there was less than 50 percent survival
of planted trees. Red pine in particular suffered greatly on
poorly drained soils. Site evaluation can be aided by use of soil maps
as well as by a more careful examination of the soil.
That the manufacture of charcoal may provide a satisfactory outlet
for the disposal of inferior material obtained in improvement cuttings,
thinnings, etc., is suggested by the Vermont station. The gross return
per man-hour of labor in charcoal production was $1.55 in both 1951
and 1952 operations. A reasonable charge for the wood entered into
the computation. Charcoal derived from wood cut the preceding
spring was more solid than that from wood cut 2 years in advance of
PLANT DISEASE INVESTIGATIONS
Agricultural research is concerned with the life sciences in their
most fundamental aspects. Especially is this true in plant pathology.
Although the plant pathology departments of experiment stations are
making satisfactory progress in developing practical methods for the
control of plant diseases, it must be kept in mind that much of this
progress has grown out of fundamental research. Many important
crops, such as wheat, potatoes, sugarcane, and fruits, could not be
grown at their present rate if it were not for the economic control of
the more devastating diseases by crop rotation, breeding, and
Plant pathologists generally direct their attention to the practical
farm problems first. But they must be concerned constantly with such
basic questions as: Why is one strain or plant resistant, whereas others
are susceptible to certain disease organisms; why do some fungicides
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United States. Office of Experiment Stations. Report on the Agricultural Experiment Stations, 1953, book, 1953; Washington D.C.. (digital.library.unt.edu/ark:/67531/metadc5989/m1/95/: accessed November 24, 2017), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.