ABSTRACTS 97 



Further tests were made to determine the changes in numbers and 

 kinds of microorganisms naturally occurring in soil solution when it is 

 dried in different types of soils, sand, sandy loam, clay, clay loam and 

 muck, using soil solution from a rich garden loam. 

 Conclusions from all the experiments were that : 



1. The survival of nonspore-bearing bacteria in air-dry soil is due, 

 in part, to the retention by the soil, of moisture in the hygroscopic 

 form. This, however, is not the only factor, for the longevity of bac- 

 teria in a soil is not directly proportional to its grain-size and hygro- 

 scopic moisture. 



2. Bacteria, at least those tested, resist desiccation longer in a rich 

 clay loam than in sand under the conditions of our experiment. 



3. The solution extracted from a rich clay loam contains substances 

 which have a protective influence upon bacteria subjected to desic- 

 cation. 



Reaction of the Soil Solution as an Index of Biological Changes in the Soil. 



J. F. Morgan and O. M. Gruzit. 



One of the essential problems in the study of soil fertility is to adjust 

 the reaction of the soil. This reaction essentially influences the chemi- 

 cal, the physical conditions and the biological life of the soil. 



The junior author has found in his preliminary study of the soil 

 solution adjusted to various degrees of reaction with n/100 mineral 

 acid and n/100 alkali and mixed with pure sterile quartz sand, that 

 this reaction had some effects upon the number and the type of bacteria. 



An acid reaction of n/1200 had a distinct toxic action on the growth 

 of the bacteria and the most suitable reaction for the growth of the 

 soil bacteria was in the neighborhood of n/1000 alkali. 



When changes occur from alkaline to neutral and to acid, the numbers 

 of bacteria increase up to the point where the solution is barely alkaline 

 and then, decrease after this point is passed. In cultures with an acid 

 reaction, the lowering of this acidity causes the soil bacteria to increase 

 rapidly. 



The Soil Solution as an Index of the Biological Changes in the Soil. 



J. Franklin Morgan. 



The soil solution is a homogeneous mixture of the soil water and the 

 soluble soil constituents, both mineral and organic. 



The soil solution offers a good medium for the study of some of the 

 biological changes in the soil. As it is the work shop of the micro- 

 organisms, this solution will contain the products of their work. 



In some nitrogenous experiments with dried blood, tankage, and 

 cotton seed meal, marked changes in the forms of nitrogen and physical 

 conditions of the solution were noted at the different periods of ex- 

 tractions. 



The longer periods showed a decrease in ammoniacal-N and an in- 

 crease in nitrate-N. In all cases there was an increase in the total 

 solids. This had its effect upon the physical conditions of the solution, 

 e.g., specific gravity, specific conductance and similar phases. 



