CHAPTER XVII 
MINERAL FERTILIZERS—NITRATES AND 
PHOSPHATES 
NITRATES 
CHARACTERISTIC OF ARID ArREAS—Minerals that are readily 
soluble in water only occur in large quantities in arid climates. 
Nitrate of soda (NaNO, Chile saltpetre), which is of great 
service as a fertilizer, is practically restricted to the almost 
rainless belt in Northern Chile and Southern Peru. 
Nitrogen is essential to the growth of most organisms, 
which are dependent on the few plants that by their nitrifying 
bacteria can extract it from the air. The volcanic eruption 
on Krakatoa in 1883 destroyed all its vegetation and soil. 
The first plants to resettle on the island were those that use 
atmospheric nitrogen, and until they had enriched the soil 
with nitrates no other plants could live there. The rotation 
of crops, the basis of scientific agriculture, depends on the 
restoration of nitrogen to the soil by a leguminous crop. 
Nitrogenous fertilizers release ordinary plants from their 
dependence on those which extract nitrogen from the air. 
The nitrate fields of Chile lie on a plain, the “ pampa,” 
between the Coast Ranges and the main chain of the Andes, 
in a belt 450 miles long, between 19° and 27° S. lat., between 
200 and 5000 feet above sea-level, and from 16 to 90 miles 
from the sea. The Coast Ranges consist of pre-Palzozoic 
gneiss and schists; the Andes are built of Paleozoic and 
Cretaceous sediments and Kainozoic igneous rocks. The 
area is one of the driest in the world. In some places a 
decade passes without a single fall of rain; in others there 
may be a few light showers every year; at Antofagasta 
after several dry years a heavy shower happened in 1910, 
two days of heavy rain fell in 1911, and more in 1912. The 
107