76 BULLETIN" 355, U. S. DEPARTMENT OF AGRICULTURE. 
means the presence of a large supply of nitrogen. This is usually so 
great that practically no attention need be given to this element, but 
it occasionally happens that acid marsh soils are so cold on account 
of their wetness that nitrification takes place with extreme slowness 
and there is not a sufficient supply of this element made available. 
Under such conditions the use of some form of lime to correct the 
acidity and hasten nitrification is very beneficial. This is discussed 
on page 62. Manure is often beneficial to marsh soils and should be 
applied when practicable. (See Kef. 3, p. 613.) 
The most marked weakness of marsh soils is with respect to the 
chemical elements, phosphorus and potassium. While, of course, 
all of the vegetation which causes the accumulation of organic matter 
in the marsh contained potassium when it was growing, this element 
is often leached out of such soils as they accumulate to such an extent 
that there is not left sufficient to supply the needs of growing crops. 
For this reason barnyard manure or some commercial fertilizer con- 
taining potassium must be used. It is frequently found that marsh- 
lands give fair yields for a few years after reclamation before this 
marked need of potassium develops. This is because some of the 
vegetable matter most recently formed still contains considerable 
potassium, and this becomes available through its active decomposi- 
tion. As a rule, however, fertilizers containing this element must 
be used on such lands within a few years after their reclamation. 
The phosphorus needs of marsh soils are quite variable. Marshes 
which were formed in regions containing considerable limestone, and 
especially in regions of glacial soils formed from limestone, usually 
contain a considerable quantity of phosphorus which was deposited 
in them from surrounding highlands and which becomes available 
to growing crops. It is often found, therefore, that marshes of this 
character are not acid and do not show a marked need of phosphorus 
fertilizers for some years after their reclamation and cultivation. 
Practically all other marsh soils do require phosphate fertilizers just 
as much as potassium. The large amount of organic matter in marsh 
soils may make profitable the use of raw rock phosphate with ordinary 
field crops. This cheap form of phosphate fertilizer therefore is often 
preferable to more expensive forms for use on such land. 
On account of the unbalanced fertility conditions of these soils, 
it is usually much more economical, when farms contain upland as 
well as marshland, to use the barnyard manure produced on the 
farm on the upland soil, which requires the nitrogen which it con- 
tains as well as the other elements, and to purchase commercial 
fertilizers containing potassium and phosphorus for the marsh soils. 
Physical management. — Marsh soils are usually very loose and 
light in structure, so that growing crops do not find a good foothold 
