352 
SOILS AND AGRICULTURE OF NORFOLK. 
Experience has shown, however, that “ muck,” as the 
Norfolk farmer calls it, is essential for the production of a 
crop, especially on the light, sandy soils of East Anglia, 
where, in addition to supplying nitrogen, the manure has a 
most important mechanical effect in improving the 
mechanical condition of the soil, making it cohesive in 
cultivation and also enabling it to retain water. 
Plants are, except in the case of the Leguminosse, only 
capable of absorbing nitrogen in the form of nitrates, and 
therefore in whatever combination the nitrogen is supplied 
it must be converted to nitrate salts before it is of any use 
to the plant. This change is affected by the bacteria which 
exist in enormous numbers in the top foot of soil. Any 
organic nitrogenous body in the soil is immediately attacked 
by them and slowly oxidized to ammonia, nitrites and finally 
nitrates, a distinct species of bacterium being responsible 
for each step in the process. Energy is liberated at each 
stage, and in this way the bacteria live. 
Plants of the natural order Leguminosse have a special 
value to the farmer. For many years it was known that 
more nitrogen was left in the soil after a crop of Leguminous 
plants had been grown than had existed there before, in 
spite of the fact that the crop itself had absorbed many 
pounds of nitrogen from the land. This apparent anomaly 
was solved by two German botanists who demonstrated that 
a special bacterium living in connection with the Legume 
was fixing atmospheric nitrogen and leaving it in the soil for 
succeeding crops. The Legume played the part of host, and 
housed the bacteria in nodules on its roots while the bacteria 
in turn deposited nitrates in greater quantities than was 
needed by their hosts, and this excess was left in the soil 
ready for any future crops. 
The wellbeing of all these soil bacteria is a matter of 
enormous importance to the farmer, and tillage operations 
are largely directed to rendering the soil as comfortable as 
