r, 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.

Fertilizer for Grass.--A fertile soil will make a good sod. A thinner
soil should have a liberal dressing of complete fertilizer at seeding
time, and the formula that has been suggested is excellent for this
purpose. If a succession of timothy hay crops is desired, the problem
of maintaining fertility is wholly changed. The nitrogen supplied by
the clover is soon exhausted, and the timothy sod must be kept thick
and heavy until broken, or the soil will not have its supply of organic
matter maintained. Nitrogen must be supplied freely, and phosphoric
acid and potash must likewise be given the soil. The draft upon the
soil is heavy, and at the same time the effort should be to have a sod
to be broken for corn that will produce a big crop without the use of
any fertilizer. The grass is the natural crop to receive the plant-food
because its roots fill the ground, and the corn should get its food
from the rotting sod, when broken. Station tests have shown that a sod
can be caused to increase in productiveness for several years by means
of annual applications of the right combinations of plant-