The Nitrogen Problem in Crop Production. 113 
(c) Other bacteria liberate nitrogen during the decomposi- 
tion of organic matter in presence of air. They cause 
much of the loss in making dung (see page 107). They act in 
the soil whenever the condition of the land becomes high ; thus 
they prevent an indefinite accumulation of fertility. One of 
the Broadbalk wheat plots receives 14 tons of dung annually, 
but the nitrogen does not increase in the soil as much as 
would be expected ; analysis shows that 130 lb. are lost each 
year. The loss is smaller where dung is only applied once in 
four years, but even so it amounts to some 30 per cent. The 
worst instance is afforded by the virgin soils of new countries, 
which, when broken up and cultivated, lose their nitrogen at a 
great rate. At the Indian Head Experimental Farm, Sask., 
Canada, the top 8 inches of soil has been found to have lost 
during the past twenty-two years no less than 1,500 lb. of 
nitrogen per acre, in addition to the 700 lb. removed during 
that period in the crops. 
No element of plant food is as liable to waste as nitrogen. 
If a farmer applies potash or phosphoric acid to his land he may 
reasonably expect to get most of it back again, but when he 
applies nitrogen he is almost certain to lose a good proportion 
of it. The sound practice is therefore to keep the nitrogen 
circulating, to crop it out and replace it, rather than to aim at 
leaving it in the soil. The most advantageous method is to 
use well-balanced manures, and thus secitre as full a return as 
possible for the nitrogen applied. An instance, showing the 
effect on the amount of nitrate washed away, has already 
been given. The following example, from the Rothamsted 
mangold plots, shows the effect on the total recovery of 
nitrogen : — 
Nitrogen 
Roots, recovered, 
tons lb. 
per acre per acre 
Badly balanced manure (organic manures and 
sulphate of ammonia) 24‘7 134'4 
Better balanced manure (the above plus potash 
and phosphatic manures) .... 29-3 172 0 
The organic manures and sulphate of ammonia supplied 
plenty of nitrogen but insufficient potash, consequently the 
plant could not make full use of the nitrogen. With a better 
balanced manure the recovery was more complete, a larger crop 
was obtained, and less nitrogen was left to get lost. The very 
heavy dressings of dung alone, or of dung and nitrate of soda, 
sometimes used for mangolds and even for potatoes, are 
wasteful, and would often be improved by substituting potash 
and phosphatic manures for some of the dung. In all farm 
practice the minerals lacking in the soil should be added at the 
appropriate place in the rotation. Liming or chalking (where- 
VOL. 69. I 
