Fertilizer Treatment 295 
FERTILIZER TREATMENT AS AFFECTING NITRATE PRODUCTION. 
I. L. BALDWIN, W. E. WALTERS AND F. K. SCHMIDT. 
Nitrate production is one of the most important problems of soil 
fertility. The ability of a soil to produce sufficient amounts of nitrate 
nitrogen for desirable plant growth over and above the natural losses, 
as denitrification and leaching, depends primarily upon soil manage- 
ment and treatment. 
The problem of the farmer is to know the methods that can be 
employed to furnish and maintain this element in available form most 
economically. Natural losses occur more readily than in the more 
stable compounds of potassium and phosphorus. 
There are many factors entering into the production saa utiliza- 
tion of this important plant food and it has been the purpose of this 
investigation to try to throw some light upon a few of them. 
REVIEW OF PREVIOUS WORK. 
It has been known for a long time that nitrates are formed from 
organic nitrogenous substances in the soil. Investigators were discus- 
sing the process as far back as the middle of the nineteenth century. 
At that time they considered it as a purely chemical process. The great 
chemist Liebig held this view and his support was probably the reason 
that the actual cause of nitrification was not discovered at an earlier 
period. Boussingalt 1860 showed that the nitrogen of nitrate was not 
derived from the air. 
It was demonstrated by Schloessing and Muntz 1878 that micro- 
organisms in the soil oxidized ammonia to nitrate. His conclusions were 
drawn from the work he did on sewage disposal. Since this time many 
attempts were made to isolate the organism in pure culture and it was 
not until about 1890 that this was accomplished. 
King and Whitson (2) found that nitrates were produced more 
rapidly in stirred soil due to better aeration. 
Brown (4) concluded that media prepared from soil extracts per- 
mitted fewer organisms to develop than the modified synthetic agar. 
Fresh soil offers conditions as closely approximating field conditions as 
possible. 
Lyon, Bizzell and Conn (5) state that a very definite relation ex- 
ists between the crop yields and nitrate contents of the soil. Higher 
yielding plots show a larger accumulation of nitrates before planting 
than do the very low yielding plots. Evidently higher yields in these 
plots are associated with a more rapid formation of nitrates. 
Brown (7) ran nitrification tests to find the nitrifying power of 
the soil. He treated the soils with dried blood and with ammonium 
sulphate. His tests show agreement to crop producing power of the 
soil, that is, the high nitrifying soils produced large crops. 
Brown and Halversen (10) concluded that the number of molds 
present in the soils fluctuated from one sampling to the next but was 
