eristics should be
known. Every farmer should have a working knowledge of these
materials--their sources, the percentage of plant-food carried by them,
and their probable availability. He should know in a general way their
advantages and disadvantages in comparison with each other.

Nitrate of Soda.--One of the best carriers of nitrogen is nitrate of
soda, which is imported from Chili, South America, where great beds
exist. The most of the impurities are removed, and the nitrate of soda
comes to us in bags holding 200 pounds, and looks much like discolored
salt. It is easily soluble in water, and usually contains a little over
15 per cent of nitrogen, which is in a very available form. Its
immediate availability brings it into use by gardeners and truckers,
and it is an excellent source of nitrogen for grass fertilizers to be
used in the early spring. It was formerly advised that nitrate of soda
should not form part of a fertilizer for use before plant-roots had
filled the ground, its high availability being supposed to lead to
heavy loss by leaching. The Pennsylvania experiment station uses it as
its sole source of nitrogen in fertilizers for staple crops on its 900
acres of farm land. It is effective in fertilizers for corn, wheat,
potatoes, and grass, as well as for special crops.

The warnings regarding loss by leaching should not be disregarded,
however. If the price of nitrogen in an organic form were as low as it
has been in nitrate of soda, and if the soils of the Pennsylvania
station farms were sandy, the use of nitrate of soda as the sole
carrier of nitrogen would be inadvisable. The only fact of consequence
is that the danger of loss has been over-stated, turning some farmers
away from the use of a good and relatively cheap carrier of nitrogen.

Sulphate of Ammonia.--This is a by-product in the manufacture of coke
and also of illuminating gas. Hunt estimates that the amount of
nitrogen lost annually in Pennsylvania's coke industry would be
sufficient, if recovered by proper type of ovens, to furnish every acre
of land under cultivation in the state with four fifths of all the
nitrogen needed to keep it in a maximum state of fertility.

Sulphate of ammonia contains about 20 per cent of nitrogen, which is in
a quite available form. It has a tendency to exhaust the lime in the
soil, producing an acid condition. Some plats in the fertilizer
experiment at the Pennsylvania station have received their nitrogen in