DECOMPOSITION OF GREEN AND STABLE MANURES 
IN SOIL 
By R. S. POTTER, Assistant Chief in Soil Chemistry , and R. S. Snyder, Assistant in 
Soil Chemistry , Iowa State College Experiment Station 
HISTORICAL REVIEW 
This paper is the third of a series of reports whose principal object is 
the determination of the rate of decomposition of original or added 
organic material in soil. This is done by the measurements at frequent 
intervals of the carbon dioxid evolved from manured and unmanured 
soils. In the first of these papers (7) 1 the effects of lime, ammonium 
sulphate, and sodium nitrate on carbon-dioxid production were deter¬ 
mined. In the second paper (8) several phases of the subject were taken 
up, the more important of which are: (1) The relation of the amount of 
air dfawn over soils to the amount of carbon dioxid evolved, (2) a deter¬ 
mination of the percentage of carbon dioxid in plots treated with varying 
amounts and kinds of organic matter, (3) a comparison of the results 
obtained by the laboratory method for the determination of carbon 
dioxid evolved from soils to the results of the determination of the per¬ 
centage of carbon dioxid in the atmosphere of soils in the field, and (4) 
determinations of the amount of carbon dioxid evolved from soils treated 
with lime and varying amounts of stable manure. The conclusions were 
briefly as follows: Within limits there was not much variation in the 
amount of carbon dioxid evolved from soil with different amounts of air 
passed over the soil. The results obtained by the laboratory method 
agreed well with those obtained in the field plots. Calcium carbonate 
accelerated the rate of decomposition of both the original organic matter 
of soil and that added in amounts of stable manure varying from 10 to 
50 tons per acre. There was less calcium carbonate decomposed in those 
soils receiving applications of manure than in those unmanured. 
A complete review of the work done in American Experiment Stations 
on green manuring published quite recently (6) calls attention to the fact 
that, while there are very little definite data concerning the effects of 
green manuring upon succeeding crop yields, yet the conclusion to be 
drawn from all the work done upon the subject is that in general green 
manuring increases crop yields. A common recommendation to farmers 
is to plow in green manure to build up the organic matter in the soil, but 
there is no definite information available as to how rapidly one may expect 
such a practice to build up the soil or as to how long, for instance, such 
1 Reference is made by number (italic) to “ literature cited”, pp. 697-698. 
Journal of Agricultural Research, 
Washington, D. C. 
li 
(677) 
Vol. XI, No. 13 
Dec. 24, 1917 
Key No. Iowa—5 
