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taken up by the soil water. This solu- 
tion is then able to dissolve many in- 
solukle minerals from the soil which are 
necessary as plant food. Such substances 
as rock phosphate and limestone, which 
are practically insoluble in pure water, 
are made soluble and available as plant 
food by the action of this carbon dioxide 
in water. 
Humus is partially decomposed vege- 
table matter. When the vegetable matter 
forms humus, or the humus breaks down 
to form still simpler compounds, heat is 
liberated. Whether a pile of leaves is 
burned or allowed to rot, the same amount 
of heat is given off in either case. This 
means that the decaying organic matter 
in the soil makes it warmer and drier in 
the spring. Thus growth will start ear- 
lier and be faster throughout the entire 
season. 
Bacteria working in the soil, especially 
during warm weather, are continually 
setting free food in the form of nitrates, 
and other minerals are also changing to 
soluble form. The nitrates, unless used 
immediately, are Hable to be lost by 
leaching away in the drainage water. 
There are some minerals also more or 
less soluble that may be lost by washing 
away in drainage water. However, their 
loss is not so great as that of nitrogen. 
To avoid this, a crop is necessary dur- 
ing the whole growing season. At the 
first of the season, the orchard while 
growing can handle and use all of this 
available plant food. Later on, when 
the orchard growth is less active, it is 
necessary to have a cover crop of some 
sort to use this food and get it in a form 
that can be carried over until the next 
season without loss. Such crops as clover 
are especially good. They not only use 
all the available nitrogen in the soil, but 
they add more from the air, and in the 
spring they decay readily, liberating their 
contents to be used by the trees. 
The ideal cultivation for orchards in 
the Central West is, we believe, inten- 
sive, clean culture from early spring to 
June, then seed to cow peas—either drill- 
ing and cultivating or broad casting. In 
this connection, the Western Fruit Grower 
says: 
ENCYCLOPEDIA OF PRACTICAL HORTICULTURE 
“Regarding cover crops for the Middle 
West, will say that we agree with you 
that nothing is better than cow peas, ex. 
cept that lots of orchards are on hills go 
steep that it will not do to give them ey. 
tivation in early spring, during the rainy 
season. We think that very soon we ghalj 
have to adopt a plan of cultivating two 
rows and leaving the next two rows in 
clover and alternating this treatment.” 
There are numerous and various vart- 
eties of cow peas adapted to the different 
orchard regions. Occasionally, we have 
followed a crop of cow peas with a crop 
of corn. During the last cultivation of 
the corn more peas are sown or hairy 
vetch. The vetch supplies a fine crop 
for plowing under in the spring. Vetch 
also becomes a profitable pasturage crop 
for hogs when their age and size will per- 
mit pasturing them without injury to 
young trees. On this subject of hairy 
vetch, Agrostologist F. Lamson Scribner 
in 1895 reported: 
“Hairy vetch sown in autumn will cover 
the ground and prevent washing during 
the winter. It is one of the best crops to 
turn under as green manure. Do not 
commence to feed hairy vetches until they 
have begun to bloom. Like most of the 
bean and clover family they are some- 
what diuretic if fed in large quantities 
before mature. Use caution in feeding 
until the animals have become accustomed 
to the change of feed.” 
Peas may be utilized in the same way 
—just as you would clover. We have occa- 
sionally used a crop of red clover but its 
use is too familiar to need further com- 
ment here. We have also used alsyke 
clover, which in some cases is better than 
red clover. 
Some sort of cover crop throughout the 
winter not only prevents washing, which 
is so disastrous, but holds the winter 
snows, and lessens the depth of alter- 
nate freezing and thawing. Also in gath- 
ering the crop in the fall, it makes pick- 
ing and hauling of fruit a much cheaper 
and cleaner job. 
The rapid growth induced by cultiva- 
tion through the first of the season is 
inclined to make the new wood of the 
trees soft and tender. To check this 
growth and harden the wood for winter, 
a cover crop is necessary. The weeds 
or volunteer grasses might be allowed to 
