52 
Colorado Experiment Station 
usually meant when we use this term. An important question in this 
connection is, If they do not come in with the alkalis where do they 
come from? These salts are characterized by the presence of nitrogen, 
which is necessary for their formation. Chile saltpetre or sodic nitrate 
is an example. It is not intended to state that this salt actually occurs 
in these soils though it may either be alone or associated with other 
nitrates. The rocks, especially the minerals from which the alkalis 
are formed are found practically everywhere in our soils and very 
abundantly in our mountains, so if our alkalis and these nitrates had 
the same origin they should have the same general distribution. This 
is not the case. We believe that we have so good as no plants which 
can do without nitrates and, as we have plants growing and bearing 
their fruit, we must accept it as proven that these nitrates are present 
wherever we find such plants growing. The characteristic thing in 
the occurrences which we are discussing is that they kill plants and, 
of course, nothing grows where they occur. The complaint that the 
ranchmen send in is almost uniformly of “brown spots” on which 
nothing will grow. These spots are usually in cultivated fields which 
are elsewhere productive and I can testify that, judging from the 
whitened surface of these fields when not covered with vegetation, 
they are at the surface, very rich in alkalis and are brown and unpro¬ 
ductive in spots only. We find these spots rich in nitrogen and es¬ 
pecially in nitrates. We all have the same practical method of consid¬ 
ering these questions. Why is not this nitrogen spread out everywhere 
just as generally as the alkali and why are these spots richer in nitrogen 
than the rest of the land? There are no deposits of these salts found 
anywhere except near or at the surface of the land. The deep portions 
of the rocks contain no nitrates for they are all soluble and have been 
washed out or destroyed as one of the changes which are going on all 
the time. 
We know how the nitrates that our plants use are formed in the 
soil. There are different kinds of little plants that grow in the soil 
that are able to change ammonia, step by step, into nitric acid, and if 
there is some alkaline substance present to take up this acid we have 
nitrates formed. This is no more strange than the fact with which 
everyone is familiar that, if we keep cider under proper conditions it 
turns to vinegar, or that buttermilk is sour. In the former case a 
plant, but a different one, has converted the alcohol of the cider into 
acetic acid, and still another plant has converted the milk sugar into 
the lactic acid of the buttermilk. There is nothing so very unusual, 
then, in the production of nitric acid or nitrates in the soil, if we only 
have the nitrogen in the right form to start with. 
In these days nearly every farmer has read, heard of, and seen 
root tubercles. If peas, clover or alfalfa will not grow, it is because 
