GROUP OF HEAVY SOILS. 
25 
the long run the loss must be made up through additions of 
phosphorus fertilizer in some form. 
The chemical analyses of the Superior silt loam and clay loam 
soils show that their phosphorus content is somewhat lower 
than the average of other silt loams and clay loams in the State, 
while the potassium content is larger. Their content of or¬ 
ganic matter is somewhat below the average of soils of this 
texture. In regard to lime they vary within very wide limits, 
in some sections the soil being acid, while in others they con¬ 
tain as high as ten to twelve per cent of lime carbonate. It 
should be borne in mind that where soils are acid the amount 
of phosphorus which they do contain is not so readily available 
to plants as in soils which are not acid. 
On good uplaid soil where dairying or general farming is 
practiced the use of 300 pounds of 16% acid phosphate or 100 
pounds of 44% superphosphate to the acre every four years 
will maintain the phosphorus supply. If much grain, potatoes 
or other crops are sold, about double these amounts should be 
used. 
On soils relatively low in fertility somewhat more phosphate 
should be used at first. This is especially true of the soils which 
have grown corn or small grain a long time without the use 
of manure or other fertilizer. 
If considerable amounts of bran or cottonseed meal are fed, 
which are relatively high in phosphorus, the supply of this ele¬ 
ment may be maintained. It would usually be necessary to feed 
at least one-half ton of bran or cottonseed meal to each cow 
on a dairy farm per year to maintain the phosphorus supply of 
the soil. Since comparatively few farmers follow this practice, 
some phosphate fertilizer should be used. 
Potassium exists in these soils in large amounts. They often 
contain over 50,000 pounds of this element per acre to a depth 
of eight inches, while they contain only 1-20 as much phosphorus. 
This potassium, however, in the form in which it exists in the 
soil is not readily available to crops and becomes so only as a 
result of chemical changes which are chiefly brought about 
through the action of organic matter. When a good supply of 
active organic matter is maintained the quantity of potassium 
is sufficient to supply growing crops almost indefinitely and it 
is only in the case of fields low in organic matter or where 
