a
week to ten days are necessary. Sometimes more, sometimes less are
required, according to the character and condition of the soil and the
season. The later moisture-conserving tillage should also be carried
on every week or ten days, according to weather conditions. It is good
practice to stir the soil after every heavy or moderately heavy rain.
Use the smoothing tools after light to medium rains and the heavier
tools after packing or beating rains. In practice from five to eight
or ten of these cultivations are necessary. The drier the season the
more necessary does frequent cultivation become.

A COVER CROP is so closely associated with tillage that it is usually
considered a part of the system. It should be sown in midsummer as soon
as tillage ceases. This time will vary from July first to August
fifteenth, depending on the locality, the rainfall, the crop of fruit
on the trees, and on how favorable the conditions for securing a good
stand of the cover crop are. The farther south the locality, or the
earlier the fruit, the sooner the crop should be sown. Absence of
sufficient rainfall necessitates a continuation of the cultivation,
both because it is necessary to conserve all the moisture possible and
because it is difficult to get a good stand of a cover crop--especially
of one having small seeds--at a dry time in midsummer.

In a year when there is a full crop of fruit on the trees cultivation
should be continued as late as possible as all the stimulus that can
thus be secured will be necessary to help the fruit attain good size
and maturity, and at the same time enable the tree properly to mature
its fruit and leaf buds for the following year. On the other hand, in
a year when there is not a full crop of fruit cultivation should be
stopped early so as to avoid forcing a too rank growth of wood and
foliage and continuing the growth of the next season's buds so late
that they may not mature and therefore may be in danger of winter
killing.

The different kinds of cover crops which may be used in the apple
orchard will be considered in the next chapter as they are so closely
associated with fertilization. Strictly speaking, however, a cover
crop is used principally to secure its mulching and physical effects
on the soil in the intervals between the seasons of tillage. In
addition to its physical and feeding effects the cover crop serves to
check the growth of trees in the latter part of the season by taking
up