required for a four-year rotation as suggested above. Where hay,
straw, potatoes, root crops or common market garden crops are sold,
very much larger amounts of potassium leave the farm than in grain
farming or live-stock farming, and in such cases potassium must
ultimately be purchased and returned to the soil, either in
commercial form or in animal manures from the cities.

Thirty Bushels for Potassium

There are some soils, however, which are not normal--soils whose
composition bears no sort of relation to the average of the earth's
crust; such, for example, as peaty swamp soil or bog lands, which
consist largely of partly decayed moss and swamp grasses. These
soils are exceedingly poor in potassium, and they are markedly and
very profitably improved by potassium fertilizers, such as potassium
sulphate and potassium chlorid--commonly but erroneously called
"muriate" of potash.

Thus, as an average of triplicate tests each year, the addition of
potassium to such land on the University of Illinois experiment
field near Manito, Mason county, increased the yield by 20.7 bushels
more corn to the acre in 1902, by 23.5 in 1903, by 29 in 1904 and by
36.8 in 1905; and the proceedings of the midsummer session of the
Illinois State Farmers' Institute for 1911 report that the use of
$22,500 in potassium salts on the peaty swamp lands in the
neighborhood of Tampico, Whiteside county, increased the value of
the corn crop in 1910 by $210,000, the average increase for
potassium being about 30 bushels of corn to the acre.

Some sand soils, particularly residual sands, which often consist