are two great classes of cover or green manure crops, leguminous
and non-leguminous. A non-leguminous crop merely adds humus and
improves the physical condition of the soil. In itself it adds no
plant food, although it may take up, utilize, and leave behind plant
food in a more available form for the tree's use. But in addition to
these benefits, leguminous crops actually add to the soil plant food
in the form of nitrogen which they have the ability to assimilate from
the air by means of bacterial organisms on their roots.

NON-LEGUMINOUS CROPS.--The most important of the non-leguminous crops
are rye, buckwheat, turnips or rape, barley, oats, and millet. The
first mentioned are the most commonly used. Also in order of
importance the following are the usual leguminous cover and green
manure crops to be used: clovers, winter vetch, soy beans, alfalfa,
cow peas (first in the South). In order to determine the relative
advisability of the use of these various crops let us now look at some
of their characteristics and requirements.

Rye is one of the best non-leguminous cover crops, especially in the
young orchard, as it does not grow as well in shade as in the open. A
particularly strong point about rye is that it grows rapidly quite
late in the fall and starts early in the spring. Starting earlier than
most crops in the spring, it makes a considerable amount of growth
before the land is fit to plow. Especially in warmer climates rye
should not be sown too early in the fall--not usually before September
1st--because of this too heavy growth. Rye is also adapted to a great
variety of soils and hence will often grow where other crops will not
do well. About two bushels of seed are required per acre.

Buckwheat is probably about equally as good as rye for an orchard
cover crop, although it does not produce quite as much organic matter.
It will germinate at almost any season of the year even if it is very
dry. It is a great soil improver because of its ability to feed and
thrive on soils too poor for other crops, due to its numerous shallow
feeding rootlets. It grows rapidly and covers the ground well, but
like rye does not thrive as well in shade. Buckwheat should not be
used to excess on the heavier types of soil as it is rather hard on
the land. One bushel of seed to an acre makes a good seeding.

Turnips or rape often make good pioneer cover or green manure crops.
They are great soil improvement crops and it is comparativ