Q40 SOIL PHYSICS, CHEMISTRY AND MICROBIOLOGY 



of 0.05 % of sulphur to the soil increases ammonia formation. Parallel 

 with this increase there is a reduced formation of nitrates, which is pro- 

 bably due to the acidity or toxic effects resulting from oxidation of the 

 sulphur. 



Calcium sulphate stimulates the growth of pure cultures of red clover 

 bacteria, both in nutrient solutions and in soil extracts. The increase is 

 the same with o.oi % as with o.i %. The growth of the clover roots is 

 therefore as strongly stimulated by calcium sulphate in a quantity of o.oi % 

 as in quantity of o.i %. In small proportions calcium sulphate increases 

 the production of red clover, as well as the formation of the nodules, while 

 concentrates of 0.05 to i % do not stimulate stronger growth. The ap- 

 plication of elemental sulphur to a cla5?'ey-sand3' soil, both in quantities 

 of O.OI % and above, stimulates the growth of red clover, though not 

 very much, without percep:ibly affecting the gro\vth of the roots or the 

 nodules. 



To sum up, according to the above experiments calcium sulphate pro- 

 duces no marked effect on the bacteria usually found present on gelatine 

 plates. Xor does it stimulate the greater growth of the legume bacteria 

 in pure cultures. It does, however, increase the production of red clover, 

 the growth of its roots and the number of their nodules. On the other 

 hand, the addition of sulphur increases ammonia formation, but reduces 

 the total number of soil micro-organisms. It slightly stimulates red-clover 

 production, but has no influence on the growi;h of its roots and the 

 number of their nodules. 



730 - Factors influencing the Survival of Dried Soil Micro-organisms; Effect of Soil Solu- 

 tion. — GiLTNER W. and LanGWORTHY H. V. (Michigan Agricultural Experiment Station), 

 in Joiirnal of Agricultural Research, Vol. V, No. 20, pp. 927-942. Wtishington, D. C.. H'lj. 



Publications on the above subject mention general!}^ known facts, 

 especially with regard to the survival of the spores, but devote no attention 

 to the effect of various types of soils on the survival of the organisms dried 

 therein. With the object of remedying this deficiency, the present writers 

 undertook a series of experiments for the following purposes : 



(i) To determine whether a micro-organism [Pseudomonas radici- 

 cola) can be protected by the solution in which it is suspended before being 

 dried in quartz sand. In the first experiment the effect of saline physio- 

 logical solutions with or without the addition of organic compounds was 

 studied. In a second experiment the eft'ect : {a) of the same solutions ; 

 [b) of a culture bouillon ; (c) of milk, was compared with that of an extract 

 of loamy garden soil. 



(2) To compare the length of life of Pseudomonas radicicola dried 

 in : [a) quartz sand : [b) garden loam. 



(3) To compare the changes produced in the numbers and species 

 of micro-organisms when a watery solution of rich garden loam was dried 

 in 5 different kinds of soil : {a) compost ; {b) sand ; {c) loamy sand ; [d) clay- 

 ey loam ; e) clay. 



The following conclusions were reached : 



(i) The survival of non-sporigenic bacteria in an air-dried soil is 



