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SOIL SURVEY OF KAUFMAN COUNTY, TEXAS 65
peas. Few livestock are kept, little barnyard manure is produced,
and the small quantities available are applied largely to gardens.
Green-manure crops, cover crops or commercial fertilizers are not
generally used. The prevailing farm practices do not maintain soil
productivity.
According to farmers the insects affecting cotton most in this
county are the cotton boll weevil, the cotton flea hopper, and the
cotton leaf worm. Damage from boll weevil infestation is most
severe on late and rank-growing cotton, especially on the bottom]and
soils. Farmers report that in the heavier blackland sections the
cotton flea hopper probably causes as much damage on the blackland
soils as does the boll weevil. The cotton leaf worm causes
severe damage during some years, and poisoning for its control is
common practice. The greater insect damage on cotton which is
making good growth explains, in part, the erratic results obtained
from soil-improvement practices. In the cotton program of 1933 a
heavy growth of cotton was plowed under on many fields. In 1934
most of these green-manured fields produced considerably larger
cotton plants but a smaller cotton yield than in 1933 on account of
more severe damage from the flea hopper.
Cotton root rot, miscalled "alkali" by some farmers, is a fungus disease
that is carried over in the soil. According to plant pathologists, it
attacks cotton, legumes, many weeds, and many cultivated plants
other than grasses. The occurrence of cotton root rot is related to
the character of the soil. Probably between 10 and 15 percent of the
area of calcareous soils of the prairies in Kaufman County is infested,
and practically none of the area of the strongly acid and of the bottom-land
soils is infested. It is confined largely to calcareous or only
slightly acid soils of the upland.
PRODUCTIVITY RATINGS
The soils of Kaufman County are rated in table 4 according to
their productivity for the more important crops. The soil types and
phases are listed in the order of their general productivity under the
prevailing farming practices, the most productive soils being at the
head of the table.
The rating compares the productivity of each of the soils for each
crop to a standard-100. This standard index represents the inherent
productivity of the most productive soil or soils of significant
extent in the United States for that crop. The inherent productivity
of a soil has been defined as the productivity the soil possessed
for crop plants, without the use of amendments, at the time it apparently
became adjusted, to the usual tillage practices and before practices
of management had altered significantly this level of production.
The productivity is expressed as the percentage, to the nearest
10 percent, of the standard. Accordingly, a soil with a rating of 50
for cotton produces an average yield of 200 pounds (50 percent of
400 pounds) of lint cotton per acre. Soils given amendments, such
as lime, commercial fertilizers, and irrigation, or unusually productive
soils of small extent, have productivity indexes of more than
100 for some crops.