Bushels. Tons. Tons. Tons.
Wheat 76,224,940 37,432 176,465 227,266
Barley 69,948,266 27,324 128,813 165,896
Oats 150,789,416 56,835 267,936 345,068
----------- ------- ------- -------
Total 296,962,622 121,591 573,214 738,230
=========== ======= ======= =======

Of course these figures, so far as the amounts of nitrogen are
concerned, can only be regarded as approximate, as it is only possible
in such calculations to obtain approximate results. Accepting these
calculations as merely approximate, they are, nevertheless, of the
highest interest and importance. It is of great importance to understand
that in the annual produce of our three common cereal crops--supposing
them to be all consumed off the farm--there is removed from the soil a
quantity of nitrogen equal to that contained in over _half a million
tons of sulphate of ammonia, and three quarters of a million tons of
nitrate of soda._

As has already been remarked, it is impossible to estimate exactly what
proportion of this total nitrogen finds its way back to the soil. In the
case of wheat, it may be pointed out that the portion which is used as a
feeding-stuff--viz., _bran_--is very much richer in nitrogen than the
flour. While, then, we are unable to estimate with any exactitude this
source of loss of nitrogen, it cannot for a moment be doubted that it is
enormous, from what has been already stated. We must remember that the
portion of the crop richest in nitrogen is that which is generally
removed--the straw which is grown in producing a bushel of wheat,
barley, or oats, containing less than half the amount of nitrogen
contained by a bushel of the grain itself.

_Losses of Nitrogen incurred on the Farm._

In addition to the loss due to removal of crops from the farm, there are
one or two other sources of loss which it may be well to briefly refer
to.

_Loss in Treatment of Farmyard Manure._

There can be little doubt that in the past a very considerable source of
loss was the improper treatment of farmyard manure. The way in which
this loss may take place will be fully considered in the chapter on
farmyard manure. Suffice it to say here, that this may take place by
volatilisation of the nitrogen as carbonate of ammonia, caused by
carelessness in allowing the temperature of the manure-heap to rise too
hig