tons of humus and had dissipated 375 pounds of nitrogen to the acre,
as compared with the ground limestone, this loss being equivalent to
37-1/2 tons of farm manure.

Other trustworthy experiments by the Maryland and Ohio Experiment
Stations confirm the Pennsylvania results in showing better crop
yields when unburned lime carbonate was used; and more extensive
experiments by the Tennessee Experiment Station also agree with the
Pennsylvania data in regard to the destruction of organic matter and
loss of soil nitrogen from the use of burned lime. If dolomitic
limestone is used, magnesium as well as calcium is thus added to
the soil.

Limestone need not be very finely pulverized. If ground so that it
will pass through a ten-mesh sieve it is amply fine, assuming that
the entire product is used, including the finer dust produced in
grinding, and it is very possible that final investigations will
show that the entire product from a quarter-inch screen is even more
economical and profitable in permanent systems.

Limestone is quite easily soluble in soil water carrying carbonic
acid. It is thus readily available; in fact, it is too available to
be durable if very finely ground; and in humid sections the loss by
leaching far exceeds that removed by cropping. In practical economic
systems of farming about two tons an acre of ground limestone should
be applied every four years, or corresponding amounts for other
rotation periods.

The essential facts relating to potassium, magnesium and calcium and
to the use and value of different forms of lime have been stated