nd demanding attention at the same time. They should be
chosen and planted so that a regular, even distribution of labor can be
maintained with as little of a rush period as possible and yet with a
minimum of idle time.

The general agricultural pattern of the region must be considered. In a
sparsely settled grain and livestock region it would be quite
inadvisable to grow strawberries or other crops which require a maximum
of hand labor during a very brief period. Berries, however, may be
perfectly well suited to sections where either transient workers or city
children can be secured with little effort.

The crop should suit from the ecological viewpoint. It must not compete
with the young, growing trees for mineral food and water, particularly
during spring and early summer when the trees make most of their annual
growth. On the other hand, if planted too close to the trees, some
intercrops may be shaded too severely to produce a normal yield.

Success in intercropping is usually found between plants which are quite
dissimilar in form and habit. Black walnuts and pasture grasses furnish
a typical example. The long taproots of the walnuts penetrate deeply
into the soil, while the grass roots are shallow and fibrous and feed
in the soil surface layer. The aerial portions of these plants are
likewise quite different, the walnuts tower high in the air, while the
grasses form their crowns on the very surface of the ground. The light
shade cast by the walnuts does not interfere with the photosynthetic
activity of the grasses, but it is sufficient to discourage growth of
broad-leaved weeds which have a higher light requirement than that of
grass. This light shade also tends to provide a greater supply of
available moisture for the grass, in that it reduces temperature and,
consequently, water loss from the grass and soil by keeping down both
transpiration and evaporation.

Experiments in both Tennessee and Ohio have shown that the quantity of
grass produced from beneath walnut trees is greater than on equal areas
in the open and that the quality, as represented by a larger protein
content, is also higher. For this reason, one may well consider
livestock as the income-producing portion of a walnut-pasture planting.
Over one fourth of the agricultural land of the United States is devoted
to pasture and much of the land is suitable for interplanting to
walnuts, butternuts, and other pasture trees, as honey locusts and black