122 INDIAN CORN CULTURE. 
in place of the beans we sowed barley and red clover together. 
The result was that the red clover sown with the barley was 
so luxuriant as greatly to interfere with its growth, and this 
too upon land where we had been trying to grow beans with- 
out manure for 30 years. In spite of our having grown a 
leguminous crop something had accumulated in the soil 
which was more favorable to the growth of another legu- 
minous plant than to that of a cereal crop.” 
Plants also differ in use of ingredients of soil 
fertility. Tobacco is notably a potash feeder, 
while the clovers use comparatively more 
nitrogen than phosphoric acid or potash. This 
being the case, one kind of plant food might 
he accumulating in the soil while a crop was 
being grown upon it which made only a slight 
drain upon that particular element. If no ma- 
nure was put upon the land it is plain, in view 
of these facts, that the land could be cropped 
to better advantage by the rotation system 
than by continuously growing the same class of 
plants on it. 
An important factor in rotation also bears 
on the plant food left in the roots of the crop 
last removed from the field. Gulley states* 
that when either red clover or cowpeas are 
grown on land of average fertility in the South 
after cutting off the crop for hay the stubble 
and roots on an acre of soil contain as much 
nitrogen, phosphoric acid and potash that may 
become available to the next crop as a dressing 
* First Lessons in Agriculture, 1892, p. 85. 
