678 
Journal of Agricultural Research 
Vol. XI, No. 13 
an application will last. It was to throw some light on this phase of the 
green manuring problem that the work reported herein was undertaken. 
In one of the papers referred to above (8) a quite complete review of 
the literature on carbon-dioxid production in soils is given, so that here 
mention will be made of only those papers which have appeared since 
the preparation of that bibliography. 
J. G. Lipman and associates (4) have at various times reported the 
results of a field experiment on the effect of a light application of stable 
manure on the decomposition of green manures. The essential points 
of the plan of their experiment are as follows: Cow manure in amounts 
varying from 1,000 to 4,000 pounds per acre is added to plots upon which 
in one series a nonlegume is growing and on the other series, a legume. 
The cow manure is plowed under with the accompanying green manure. 
This plan has been followed for several years. Crop yields and the 
amount of nitrogen in the crop are noted, from the fact that crop and 
nitrogen yields have been somewhat larger on those plots receiving the 
cow manure plus the green manure than on the ones receiving the green 
manure, they have concluded that the cow manure enhanced the rate of 
decomposition of the green manure. Also, those plots receiving the 
larger amounts of cow manure did not always give greater crop yields 
than those receiving the smaller. This, too, is interpreted as being in¬ 
dicative of an increase of the rate of decomposition of the green manure 
by the cow manure. 
In 1916 Boltz (j) published the results of an interesting experiment 
with clover used as a green manure. Green clover at the rate of 7,744 
pounds per acre was applied to two small areas, in one case merely put 
on the surface and in another spaded under. The clover and soil were 
analyzed for organic matter at the beginning of the experiment and the 
surface application of clover was collected at the end of the experiment 
and the amount of organic matter remaining was determined. The soil and 
soil and clover mixture were analyzed at the end of the experiment also. 
Throughout the course of the experiment, which ran from October 12 to 
May 5, 206 days, 66 per cent of the clover applied to the surface was lost, 
while 28.45 per cent of it was lost when it was incorporated with the soil. 
In a similar experiment, but carried out in a lysimeter and involving 
treatments of clover of 17,520 pounds per acre, 68.5 per cent of the 
organic matter of the clover was lost when applied to the surface and 
58.5 per cent when spaded in with the soil. Only about 1 per cent of the 
organic matter of the clover was lost by drainage. The results obtained by 
Boltz are interesting when compared with those reported in this paper. 
EXPERIMENT I 
Part of the large sample of Miami silt loam soil that was used in the 
former experiments of this series (7, 8) was used. Practically the same 
apparatus was used as formerly, the only difference being that, instead 
of putting the soil in pots under bell jars, it was placed in the ordinary 
