MAINTAINING THE SOIL FERTILITY 293 
possible that the factors above discussed, if properly 
applied, could liberate the latent plant-food of the 
soil and gather all necessary nitrogen for the plants. 
Such an equilibrium, could it once be established, 
would possibly continue for long periods of time, but 
in the end would no doubt lead to disaster; for, 
unless the very cornerstone of modern agricultural 
science is unsound, there will be ultimately a dimi- 
nution of crop producing power if continuous crop- 
ping is practiced without returning to the soil a goodly 
portion of the elements of soil fertility taken from it. 
The real purpose of modern agricultural research is 
to maintain or increase the productivity of our lands; 
if this cannot be done, modern agriculture is essen- 
tially a failure. Dry-farming, as the newest and 
probably in the future one of the greatest divisions 
of modern agriculture, must from the beginning 
seek and apply processes that will insure steadiness 
in the productive power of its lands. Therefore, 
from the very beginning dry-farmers must look 
towards the conservation of the fertility of their 
soils. 
The first and most rational method of maintaining 
the fertility of the soil indefinitely is to return to the 
soil everything that is taken from it. In practice 
this can be done only by feeding the products of the 
farm to live stock and returning to the soil the ma- 
nure, both solid and liquid, produced by the animals. 
This brings up at once the much discussed question 
