"I can't understand that," said Mr. Thornton. "How can that be when
one of the crops is cowpeas?"

"In average live-stock and dairy farming," Percy continued, "about
one-fourth of the nitrogen contained in the food consumed is
retained in the milk and animal growth, and you can make the
computations for yourself. It should be kept in mind, moreover, that
much of the manure produced on the average farm is wasted. More than
half of the nitrogen is in the liquid excrement, and it is extremely
difficult to prevent loss of the liquid manure. There is also large
loss of nitrogen from the fermentation of manure in piles; and when
you smell ammonia in the stable, see the manure pile steaming, or
colored liquid soaking into the ground beneath, or flowing away in
rainy weather, you may know that nitrogen is being lost. How many
tons of manure can you apply to your land under such a system of
farming as we have been discussing?"

"Well, I've figured a good deal on manure," was the reply, "and I
think with four fields producing such crops as you counted on, that
I could possibly put ten or twelve tons to the acre on one field
every year."

"That would return from 100 to 120 pounds of nitrogen;" said Percy,
"instead of the 173 pounds possible to be returned if there is no
loss. There are three methods that may be used to reduce the loss of
manure: One of these is to do the feeding on the fields. Another is
to haul the manure from the stable every day or two and spread it on
the land. The third is to allow the manure to accumulate in deep
stalls for several weeks, using plenty of bedding to absorb the
liquid and keep the animals clean, and then haul and spread it when