368 
S0IL8 AND AGRICULTURE OF NORFOLK. 
On the other hand as it is from the clay that most of the 
soluble mineral food is claimed, clay soils contain a high 
potential fertility, and if the texture of the soil can be 
improved or kept open, heavy crops may be obtained from it. 
The finely divided iron oxide has here interfered with the 
analyses, as much of the “ clay” and silt fractions consisted 
of that substance. 
Table V. 
Chemical analysis of some Lower Greensand Soils : — 
Constituent. 
West 
Dereham. 
Dersing- 
ham. 
Heacham. 
Moisture . . 
1-23 
1-55 
295 
Organic and loss on ignition 
4-02 
5-10 
7'55 
Nitrogen . . 
•132 
167 
•182 
Potash 
•223 
146 
•337 
Phosphorus pentoxide 
•264 
■243 
•348 
Calcium and magnesium 
carbonate 
T3 
•23 
'57 
Insoluble residue 
86-47 
8027 
64-49 
The above table of these lower greensand soils, arranged in 
order of fertility, shows clearly how good farming by increas- 
ing the amount of humus is the soil assists the fertility. 
The Heacham soil is much more productive than the 
Dereham one, while the total amounts of potash and 
phosphorus differs by very little. 
Analysis of greensand soils is rendered exceedingly difficult 
as so much iron is dissolved out by the strong hydrochloric 
acid used. It exists as finely divided iron oxide and is very 
difficult to filter off or otherwise separate. 
The greensand outcrops along the line of parishes — 
Heacham, Dersingham, Wolferton, Castle Rising, Bawsey. 
Ashwicken, Mintlynn, North Runcton, Downham Market, 
and West Dereham — give rise to a very well marked type 
