INTRODUCTION, 37 
thrive in soils rich in lime and full of air; they perish 
in a wet sour soi]. Thus the alfalfa filled all the soil 
with its rootlets, going down often as far as 6 feet, 
no doubt, and numberless millions of bacteria work- 
ing there were storing the soil with nitrogen drawn 
from the air. The phosphorus supply may have 
been somewhat deficient; we bought phosphorus for 
part of the land and added that. Then the land was 
plowed; the plow cut off millions of those big roots 
and left the top soil one mass of roots, with also 
many little rootlets and many leaves and stems that 
had fallen down. And the subsoil was made porous 
by being honeycombed by millions of the tap roots, 
so the air penetrated all the more easily. Thus it is 
seen that conditions for a big corn crop were almost 
ideal. 
It would be an interesting thing to know just how 
much richer Woodland Farm is than it was before 
alfalfa began to grow uponit. It is safe to say that 
the alfalfa, yielding on the average 300 tons of hay 
per year for the past ten years, has added to the soil 
plant food worth at least $3,000 each year, count- 
ing the manure that has been returned and the work 
of the roots; probably this is an underestimate, in 
fact. Once we racked our brains to find manure 
enough, and never did find enough. Now we rack 
our brains again to find time to haul out the manure 
that is made upon the farm. Gathering fertility by 
the use of alfalfa is like rolling a snowball—the 
farther you roll it the faster it gathers. This would 
not be true if the hay was sold off of the farm, but 
