10 
COLORADO EXPERIMENT STATION 
time it could not be shown that the fertilizers had in any case produced 
an increased yield over the unfertilized plots. 
How then, are we to maintain the fertility of our orchard lands? 
We have already seen what the benefits are of plowing under alfalfa 
to wheat and potatoes, so why not adopt a system of green manuring 
for the orchard? The Greeley potato growers do not think of grow¬ 
ing more than two crops of potatoes after alfalfa has been turned 
under. If they can afford to grow alfalfa for the purpose of producing 
better potatoes and in the meantime get but two crops in five 
years,, surely the orchardist can adopt similar methods. There will 
be no rotation with the orchard crop but an actual saving in labor may 
be made in that there is little or no cultivation while the green manure 
is occupying the ground. The potato grower gets some returns, to be 
sure, from the alfalfa hay and from the grain with which it is seeded 
but the potato crop is the money maker. 
We have already noticed what some of the effects of plowing under 
green crops are. But the importance of the subject will warrant a 
repetition. The following summary has been adapted in part from 
Professor Bailey’s writings on cover crops: 
I. Green manures improve the physical condition of the land: 
Shade the surface soil from intense sun in summer thereby protecting 
the trunk and limbs from the reflection of the sun from the soil; 
prevent the very rapid burning of organic matter in the soil; con¬ 
serve some of the surface moisture, and prevent crusts from form¬ 
ing.. 
Prevent soils from cementing and puddling. 
Prevent the rapid drainage of water from loose, porous soils. 
Prevent one form of freezing dry. 
II. They catch and hold some of the leaching nitrates; 
Render plant food materials available; 
Appropriate nitrogen if legumious crops are grown. 
Cover crops have become very popular in the East in orchard 
management. The name is derived from the fact that the seed is 
sown in the fall or late summer and sufficient growth results so that 
the ground is covered and protected during the winter. The crop is 
intended primarily for a green manure but under eastern conditions 
it cannot occupy the land during the growing season. The trees 
usually need all of the available moisture during that period and clean 
cultivation is practiced to conserve it. As soon as the trees have made 
their growth for the season the cover crop is planted and its growth 
uses up the surplus moisture and thus the trees are aided in maturing 
before cold weather comes on. Colorado conditions are quite different 
from the fact that the water is largely under man’s control. We 
believe that our conditions demand a cover for the soil far more 
in the summer than during the winter. And moreover, nearly as much 
protection is afforded during the winter if the crop is plowed under 
late in fall, as is the case when the plants are allowed to stand. We 
therefore propose the name, shade crops, for a system which we hope 
may come into general use in this state. 
Many orchardists have seen young trees killed by running water 
close to them during a hot day; the reflection of the sun from the 
