The Choice of Crops for Alkali Land Page: 8
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THE CHOICE OF CROPS FOR ALKALI LAND.
EFFECT OF ALKALI UPON PLANT GROWTH.
The harmfulness of alkali depends not only upon the quantity and
the kind of salts, but also upon the amount of moisture the soil con-
tains. The soil moisture is controlled by climatic conditions (rain-
fall, evaporation, etc.), by the frequency and heaviness of irrigation,
by the texture of the soil, and by the conditions for drainage. Fur-
thermore, the distribution of the salts in different depths of the soil,
in relation to the character of the root system of the plant, must be
taken into consideration.
COMPARATIVE HARMFULNESS OF DIFFERENT KINDS OF ALKALI.
The sulphates, chlorids, and bicarbonates, collectively known as
"white alkali," are much more abundant in most localities than the
carbonates, or " black alkali."
Black alkali, which can usually be recognized by the dark color it
imparts to the surface soil and to standing water,' is far more injuri-
ous to plants than the white-alkali salts. It is a strong corrosive,
causing the decay of plant tissues. Trees growing in black-alkali
land are sometimes completely girdled at the crown through the cor-
rosive action of the sodium carbonate. This salt also has a bad effect
upon the texture of heavy soils, causing them to become puddled.
Where the soil contains considerable black alkali it is useless to
attempt to grow crops until this condition is remedied. If gypsum,
or land plaster, can be obtained at a reasonable cost, and the value
of the land warrants its use, the black alkali can often be converted
to less harmful salts by successive applications of this fertilizer. The
effect of the gypsum is to neutralize chemically the black alkali.
This results in loosening the soil, making it easier for water to pene-
trate, and aiding the washing down of the other salts. The presence
of more than one-tenth of 1 per cent of sodium carbonate is injurious
to the growth of practically all crop plants. For most species one-
twentieth of 1 per cent (0.05 per cent) of this extremely noxious salt
is too much for good crop production.
The white-alkali salts are not corrosive, but when freely taken up
into the cells of the plant they cause serious disturbances in its nutri-
tion. If present in the soil in sufficient quantity, these salts also hinder
the absorption of water by the plant roots, so that even when the soil
is quite wet the plants may actually be suffering from lack of water.
This is doubtless one of the chief reasons why seeds germinate more
slowly where alkali is present.
The chlorid type of white alkali is somewhat more harmful to most
crop plants than the sulphate type. The bicarbonates as such do not
1 This indication is sometimes misleading, however, for the dark color may be pro-
duced by less harmful salts, and the carbonates themselves may not produce the stain if
the soil contains but little humus.
4468
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Kearney, Thomas H. (Thomas Henry), 1874-1956. The Choice of Crops for Alkali Land, pamphlet, 1911; Washington D.C.. (https://digital.library.unt.edu/ark:/67531/metadc87533/m1/8/: accessed April 23, 2024), University of North Texas Libraries, UNT Digital Library, https://digital.library.unt.edu; crediting UNT Libraries Government Documents Department.