60 HINTS ON SOILS AND FERTILIZERS 
CROP ROTATION AND SOIL FERTILITY 
There is a close relationship between the 
rotation of crops, and soil fertility. By rota¬ 
tion of crops, we simply mean that for any 
given field on a farm, a different crop is raised 
each year, instead of raising the same crop on 
the same piece, year in and year out. This 
practice of rotating the crops each year on the 
farm is not a new system, nor can it be said 
that it is a comparatively old idea. In fact, 
many of our forefathers used to plant wheat 
on the same piece of land, year after year, un¬ 
til the crops dropped to such a low yielding 
stage, that it was no longer profitable to raise 
wheat on these lands. It is a generally ac¬ 
cepted idea now that rotation of crops is the 
only sane method for permanent agriculture. 
We have already noted that different plants 
take varying amounts of plant food from the 
soil in one season. Let us take a specific in¬ 
stance to make this a bit clearer. Suppose that 
we grow corn on a piece of ground for five 
years in succession. What is the result? Is 
the fifth year’s crop as large as the first year’s 
crop? No, ordinarily, we would find quite a 
difference in the two yields. Then why is the 
last crop so much below the first one in yield? 
Corn is a heavy feeder of nitrogen, the ordi¬ 
nary corn crop on one acre, in one season, re¬ 
moving about 95 pounds of nitrogen. By rais¬ 
ing corn in succession for five years, we find 
that we are drawing unusually heavily on the 
nitrogen supply, with the result that the amount 
