PRESS BULLETIN No. 107.
January 30, 1909.
lorida Agrlcullural Experiment Statlon.
SOME UNFAVORABLE SOIL CONDITIONS.
BY A. W. BLAIR.
It quite frequently happens that crop failures are due to unfavorable soil
conditions rather than to a deficiency of plant food in the soil, and the ability
to at once recognize such conditions and correct them will save the farmer
Among such unfavorable conditions the following may be mentioned:
(1) Hardpan; (2) the presence of iron salts; (3) excess of water; (4)
lack of water; (5) the presence of acids in the soil.
By hardpan is meant a more or less hardened layer at some depth in
the subsoil. It may be comparatively near the surface, or it may be several
feet down. Hardpan obstructs the free growth of the roots downward in
their search for food and water, and it may also prevent the free movement
of the water downward, thus causing the soil to become water-logged during
a rainy period; or it may prevent the free movement of the capillary water
,upward to the plant roots during a dry season. Hardpan may be calcar'ous,
siliceous, or ferruginous (iron-bearing). The cementing materials go to
solution near the surface and filter through into the subsoil, until
particular level, where the subsoil may be naturally close-grained,
trialss are deposited year after year in a layer which gradually
thicker and harder. If the plants or trees begin to show signs of tr
examination of the subsoil should be made-not stopping at on
feet-and if hardpan is found it must be broken up, either by deep
by digging, or as a last resort by the use of dynamite. The ad
air to this hard layer and the re-establishment of water circulation
to soften the hardpan.
Sometimes an artificial hardpan, or "plowsole," is formed wh
always plowed to the same depth. This could be avoided by oc
Iron is often found in quantity in the soil as an oxide, or hy
in these forms it does but little if any harm. Their presence
recognized by the yellowish to reddish hues which they give t
On the other hand iron pyrites and salts of iron such as ferrou
and ferrous carbonate are poisonous to plants. Some of these pois
salts give to the soil a bluish or greenish color which is characteristic. This
condition may be remedied to a certain degree by thoroughly stirring teo
soil, so that the air may circulate through it more freely. This tends to
oxidize the poisonous compounds and make them harmless. Where iron
salts are present in considerable quantity, it is possible for them to com-
bine with the phosphoric acid of the soil and hold it in a form that is not
readily available to plants. The free use of lime or finely ground limestone,
together with thorough aeration will usually prove effective where poisonous
iron compounds are present.
EXCESS OF WATER.
It is well known that plants do poorly in a water-logged soil. Under
such conditions the air cannot circulate freely, the beneficial bacteria do not
develop, and acid tends to accumulate. The remedy is to drain the land,
thus getting rid of the surplus water, and then to plow deeply in order that
the air may circulate freely and oxidize any poisonous substances that may
have been formed.
LACK OF WATER.
A lack of water can often be remedied, at least partly, by more frequent
and thorough cultivation, thus preventing excessive evaporation from the
surface. The incorporation of humus or humus-forming materials with the
soil will enable it to hold more of the water that falls upon it. This may be
done by growing cover crops such as beggarweed, velvet beans, or cowpeas,
and by leaving in the soil-not burning-the remains of plants.
Organic acids are formed by the gradual decay of organic matter in
soil. If there is a deficiency of lime these acids will accumulate and fl
cause trouble. When such acids are present in considerable quantities
interfere with the development of the nitrifying bacteria, and thu
the supply of available nitrates for crop production. The acid condi
be remedied by a liberal application of lime or finely ground limes
further treatment of acid soils see Bullein 93, which will be sent
State papers please copy.