362 
SOILS AND AGRICULTURE OF NORFOLK. 
Of late years, however, the farmer has only been required 
to farm reasonably and without diminishing the fertility of 
the soil, and this freedom has allowed new methods and 
crops to come into use where the nature of the soil allows. 
Soil Analysis. 
The analysis of a soil involves two distinct series of 
operations : — A chemical estimation of the elements forming 
the soil minerals and a mechanical separation of the 
different sized particles of which a soil is composed. To 
ensure uniformity of results amongst chemists, the Agricul- 
tural Education Association in 1900 recommended a set of 
conventional methods both for obtainine samples and for 
carrying out the necessary separations. The only absolute 
figures possible are those obtained by an ultimate elementary 
analysis of the soil, but this is never attempted in practice, 
only constituents of importance to the plant, such as nitrogen, 
potash, phosphorus, silica, carbonates, calcium, and organic 
matter being quantitatively estimated. The various-sized 
particles are separated in six fractions, which each contain 
particles of approximately the same character as far as size 
is concerned. 
Owing to the fact that it is extremely difficult to break 
down completely the complex salts forming minerals in the 
soil, chemical analysis give results that are comparative 
only. For example, an analysis made at Rothamsted of 
soil from the famous “ Broadbalk ” wheat field gave by the 
ordinary method of extraction, potash 5 per cent., while the 
same sample thoroughly broken down by hydrochloric acid 
yielded 2‘26 per cent, potash. 
The percentage extracted by the usual means, however, 
indicates very well the amount of potash in such a state of 
combination that it is ever likely to be available for the use of 
the plant, and so a total breaking up of the soil is unnecessary 
in practice. In the chemical analysis, nitrogen is estimated 
