480 
AGRONOMY: C. B. LIPMAN 
to render impossible the proper activation of those organisms. To all 
such direct damage to the soil must be added the indirect damage to 
the water and air supply necessary for the bacteria which follows the 
loss of organic matter from soils. 
Still other considerations of a theoretical nature enter into the 
problem. These are concerned with the causes for the unsatisfactory 
nitrification of the nitrogen in dried-blood, for example. We have 
noted in all of our experiments that ammonification of dried-blood 
nitrogen may proceed with vigor in the soils in question while no 
nitrate is produced. It appears now that in soils which produce am- 
monia most energetically from dried-blood nitrogen that the nitrifying 
bacteria are deleteriously affected by the ammonium carbonate and 
gaseous ammonia which the soils in question liberate in large 
quantity. Whether this speculation be correct or incorrect will appear 
from experiments which are now in progress. It appears certain how- 
ever, regardless of the outcome of these experiments, that the fermenta- 
tion of dried blood proceeds very differently in the 'normal' and the 
'abnormal' soils which represent respectively those which nitrify the 
nitrogen of dried blood and those which do not. In the former soils 
no odor of ammonia is ever noted in the soil cultures and no other 
odors but those of active soil are encountered. In the latter soils not 
only is ammonia given off in large quantities, but it is accompanied by 
ill-smelling gases resulting from putrefaction. 
The brief space of this paper precludes the possibility of a more de- 
tailed discussion of the large amount of experimental data which we 
have accumulated in our experiments with both humid and arid soils; 
but it may suffice here to point out some of their practical bearings. 
1. The addition and maintenance of a good supply of organic matter 
by green manuring or by the use of barnyard manure must be prac- 
ticed on all soils deficient in nitrogen and organic matter. 
2. Nitrogenous fertilizers when employed on such soils must be either 
of the low-grade organic variety such as steamed bone meal, cotton- 
seed meal, and sewage sludge, or else sulphate of ammonium must be 
used. 
3. The overheating of the soil, excessive evaporation of moisture, 
and oxidation of organic matter should be prevented through the use 
of some kind of straw or manure mulch. This is to be regarded as 
one of the most important measures for present and future soil man- 
agement in California orchards and vineyards, when nitrogen and organic 
matter are deficient. 
^Univ. Col. Pub., Btill. Col. Agric. Exp. Sla. 
^The Intensity of Nitrincation in Arid Soils, Proc. Amer. Soc. Agron, 4. 132 (1912). 
