168 FORAGE CROPS 
time, and investigation of the composition of 
the two showed that this difference was due to a 
larger proportion of nitrogenous substance in the 
clover than in the timothy. 
It is now known that the individual members of 
this group of plants possess the peculiar property 
of being able to secure the important element ni- 
trogen, in part, at least, from the air. Therefore, 
they may not need nitrogenous fertilizers after they 
are well established, and they may add to the 
nitrogen content of the soil when they are returned 
to the earth. The advantage of leguminous crops 
to the feeder lies in the fact that the plants 
themselves contain a larger proportion of nitroge- 
nous matter than those of the grass family, and 
thereby may be used to supplement other foods 
and to reduce bills for purchased and concentrated 
feeds. One can more profitably utilize the carbo- 
hydrates usually contained in excess in other 
plants; and he is relieved of some of the necessity 
of purchasing nitrogenous fertilizers to increase 
the growth of the cereal crops. 
Soil inoculation 
While leguminous crops possess this superior 
advantage in the ability to appropriate nitrogen, it 
must be remembered that this power 1s not constant 
for all soils and under all conditions; but in order 
