Maintaining Fertility
Categories:
MIXTURES FOR CROPS
A heavy clover sod gives assurance that a good
crop of corn or potatoes can be grown. If the amount of plant-food in
the sod is not excessive, a heavy crop of wheat can be produced. The
condition of the soil favors many crops. The clover has placed it upon
a productive basis for the time being.
The object that should be kept in view, when a scheme of soil
fertilization is worked out, is the maintenance of
such a state of
fertility that the land can be depended upon for whatever crop comes
round in the rotation. When a 3-10-6 fertilizer, or a 3-8-10
fertilizer, is used, the effect upon a thin soil is to restore it
temporarily to this good-cropping power, the size of the application
varying with the crop. A richer soil may want the phosphoric acid and
potash without the nitrogen. A manured soil may need only the
phosphoric acid. The purpose of the fertilizer in any case is
maintenance or increase of fertility, and when this object has been
secured, the crop may be whatever the rotation calls for. It is this
rational scheme that gives success to the Pennsylvania station's
methods on some of its test plats. A given amount of plant-food is put
upon the land, which is under a four-years' rotation. One half of it is
applied every second year. The corn gets one half because it can use it
to advantage. The oat crop that follows finds enough fertility because
the soil is good. Next in the rotation is the wheat, and the wheat and
timothy and clover plants can use fertilizer with profit. There is no
change in its character because it is the soil that is getting the
assistance, and not primarily just one crop in a rotation. The land in
this experiment that is well fertilized is more productive than it was
thirty years ago, although no manure has been applied, and it is the
general productive condition that assures good yields, and not chiefly
any one application of fertilizer.