On Broadbalk Field at Rothamsted, England, wheat has been grown on
the same land every year for about two-thirds of a century. As an
average of the sixty years, 1852 to 1911 the yield was 12.6 bushels
an acre on unfertilized land, 14.6 where mineral plant food was
annually applied, 20.3 where nitrogen salts alone were used, and 37
where both nitrogen and mineral plant food were applied.

During the thirty years, 1882 to 1911 the average yields were 11.7
bushels an acre on the unfertilized land, 14 with minerals, 18.7
where only nitrogen salts were used, and 38 where both nitrogen and
minerals were regularly supplied.

These absolute data from the oldest agricultural experiment station
in the world should help us to understand why the ten-year average
yield of wheat is 33 bushels an acre for all of Great Britain,
37-1/2 for England alone, and only 14 for the United States.

The application of nitrogen increased the yield of wheat by 24
bushels an acre--from 14 to 38 bushels--as an average of the last
thirty years, following an average increase of 26.3 for the nitrogen
applied during the previous thirty years. It is true that the cost
of the fertilizers used exceeded the value of the increase in yield;
but let us bear in mind that this truth does not destroy the other
truth.

Prove all things, and hold fast that which is good. It is a good
fact that 1218 bushels of wheat were produced by the application of
nitrogen to an acre of land during a period of sixty years, over and
above the produce of another acre which differed only by not
receiving nitrogen; whereas the total produce from an acre of