8 
The Colorado Experiment Station. 
two years, it is the opinion of some authorities and many of the 
best practical farmers that it would do most good if left tluee 
years. Some think that even six or seven years would be better. 
Winter sheep feeding has changed the rotation to some extent. 
When enough sheep are fed to produce a good coat of manure 
for the potato fields, potatoes are followed with potatoes twice 01 
potatoes once and once with beets. Very substantial gains in 
yield of both potatoes and beets have resulted where manure has 
been used. The use of manure on land here as well as in the 
Eastern states is cumulative in its effects and benefits particularly 
the*heavy soils in two ways. The physical condition of the soil 
is improved by being made more porous and friable so that it 
will hold moisture better and of course, plant food is also added 
to it. 
Plowing. In the preparation of the land for potato growing 
the plowing is not the least important. This is sometimes done 
in the late fall but more commonly in the spring from the latter 
part of April to May 15 th. Fall plowing gives good results but 
ordinarily time for doing the work cannot be found at that season 
or the land may be too dry to make plowing possible. The depth 
of plowing ranges 'all the way from six to twelve inches but 
nearly as many plow eight inches deep as all other depths taken 
together. The work is generally done with four horses and a 
14 - 16 ” plow. When alfalfa is being broken the plows used have 
a wide share so that all the alfalfa roots are cut off at the bottom 
of the furrow. 
A practice that is to be commended in other places as well 
as on the irrigated land of Colorado is that of following the plow 
immediately with the smoothing harrow. This is done partly to 
mellow the soil and prevent the formation of lumps but mostly to 
conserve the moisture. Experiments have demonstrated that the 
loss of moisture by evaporation is much-less where this is done 
than where the plowed land remains for a time without harrowing. 
In this State the practice is to harrow all the land that is plowed 
each half-day before leaving the field. 
Harrowing and Leveling. In many fields scrapers are used 
after the first harrowing to fill the hollows and take down any 
ridges that are liable to cause trouble in getting water evenly 
distributed over the field. The amount of work required to fit the 
land for planting after the first harrowing and leveling depends 
on the character of the land. With average loamy soils one or 
two subsequent harrowings are sufficient to put the soil in per¬ 
fect condition for planting. If the soil is heavy or has been 
packed by rains, the disk harrow is used and followed by the 
smoothing harrow. 
