44 The Colorado Experiment Station. 
p. p. m. nitrogen as nitrites and o.i p. p. m. of nitrogen as nitrates, 
which could scarcely be possible if the surface salts were washed 
down into this ground water to any extent, and contrariwise all 
of these samples agree in leading us to most extremely improbable 
conclusions if we consider them to be the source of the nitrates. 
While this is not yet an extreme case the results are most striking 
and most evidently false, for if this ground water were the source 
of the nitrates and it were as rich as this drain water we would 
have to assert that 40,122 acre-feet of it had been evaporated to 
dryness on each acre of this orchard which would mean a mass 
of water 7.5 miles deep. This amount of water would deposit 
541,670.6 tons of salt on each acre of which only 3.25 tons, the 
amount now present in the top two inches of this soil, would be 
nitrates, and the time required to effect this, assuming the evap¬ 
oration to take place from a free water surface at the rate of five 
feet per annum, would be 48,128 years. The facts, on the contrary, 
are that these apple trees grew healthily for ten years or more 
until within the last two or three years which is conclusive proof 
that these nitrates were not present previous to this time, say three 
years ago, in sufficient quantities to do any damage, but within 
this time the limit of tolerance has been passed and this orchard has 
been destroyed. 
It is evident from the results in all the cases of ground waters 
given that it is not water derived from the surface of the land 
which has passed through the soil and now forms a sheet of water 
beneath this soil but probably represents, in large measure, the 
leakage from the irrigating ditches and other similar sources, for 
we have already given samples of such waters as have without any 
reasonable doubt come from the soil, i. e., passed through the soil 
of nitrate areas, and they are rich in nitrates. Further, this ground 
water, especially the drain water previously given owes its imme¬ 
diate origin to the gravel which underlies the sand, and which, as 
elsewhere stated, constitutes the natural drainage of this section. 
I do not know whether the section where the well is located is 
underlaid by gravel or not, but the water agrees with the others here 
given in containing so good as no nitrates. Another point is the 
absence of ammonia and nitrites from this drain water, which can 
only be interpreted as indicating that no reduction of nitrates can 
have taken place in the areas from which this water came. The 
reader is referred to Analysis IX, Colorado Experiment Station 
Bulletin 155, pp. 12 and 13, for the description and composition of 
a water derived from a nitre soil. We cannot extend the considera¬ 
tion of this subject at this time. 
Case No. 16 —Orchard No. 3, described in Bulletin 155, pp. 
16-18, has grown worse and many trees, not previously described. 
