516 EXPERIMENT STATION RECORD. [Vol. 36 



sulphate, potassium chlorid, magnesium chlorid, sodium clilorid, manganous 

 chlorid, magnesium sulphate, manganous sulphate, potassium nitrate, ferric 

 chlorid, manganous nitrate, sodium nitrate, magnesium carbonate, calcium sul- 

 phate, ferrous carbonate, ferric nitrate, potassium carbonate, sodium carbonate, 

 manganous carbonate, and calcium carbonate. The last two were not toxic 

 in any of the concentrations used. It was not necessarily those compounds 

 which become toxic in the lowest concentrations which were most toxic in 

 higher concentrations, as the toxicity of some salts increased more rapidly 

 than the toxicity of others. It is considered evident that the increased osmotic 

 pressure exerted by the salt added to the soil plays a great part in the retard- 

 ing of the bacterial activity but that it is not the only factor. 



" The common soil 'alkalis,' sodium chlorid, calcium chlorid, sodium sul- 

 phate — and the less common one — calcium nitrate, are very toxic to ammoni- 

 fying organisms, and if present in soil to any great extent will greatly reduce 

 the ammonia produced in such a soil. 



" Calcium chlorid, calcium nitrate, potassium chlorid, potassium sulphate, 

 magnesium nitrate, and sodium sulphate failed to increase the ammonia pro- 

 duced in a soil. All of the others, however, in some of the concentrations 

 tested acted as stimulants. The extent of the stimulation and the quantity of 

 salt necessary for maximum stimulation varied with the compound. In the 

 order of increasing efficiency they are magnesium chlorid, manganous chlorid, 

 potassium nitrate, ferric nitrate, magnesium carbonate, calcium sulphate, ferric 

 sulphate, magnesium sulphate, sodium chlorid, sodium nitrate, ferrous car- 

 bonate, potassium carbonate, sodium carbonate, manganous carbonate, calcium 

 carbonate, manganous nitrate, ferric chlorid, and manganous sulphate. Those 

 compounds which are most active as stimulants to the higher plants are also 

 most active in stimulating bacteria. . . . 



" The quantity of sodium chlorid, calcium chlorid, potassium chlorid, and 

 magnesium chlorid required to reduce the ammonifying powers of the soil to 

 half normal is practically the same as the quantity necessary to reduce the 

 growth of wheat to the same extent. The ammonifying organisms are ap- 

 parently more resistant to the other compounds tested than are the higher 

 plants." 



Fifty-seven references to literature bearing on the subject are cited. 



A preliminary report on muck humus as a fertilizer and carrier of bene- 

 ficial soil bacteria, T. F. Manns and J. M. Goheen {Dclaivare Sta. Bui. 115 

 (1916), pp. S-40, pis. 13). — It was found in the studies here reported that muck 

 such as is found in the trucking districts of northern New Jersey, although nor- 

 mally low in beneficial soil bacteria (containing a limited number of clover nod- 

 ule bacteria only ) , becomes a very favorable medium for the growth of such bac- 

 teria when properly balanced and reinforced, especially with basic substances. 

 Forty dilTerent combinations or composts were tested in these studies. Among 

 those giving the best results with nodule-forming bacteria were (1) muck 2,000 

 lbs., Thomas slag 15 to 50 lbs., carbohydrate 30 to 60 lbs., inoculating soil 25 lbs. ; 

 (2) muck 2,000 lbs., potassium carbonate 10 lbs., acid phosphate 50 lbs., calcium 

 carbonate 100 lbs., carbohydrate 30 lbs., inoculating soil 25 lbs. ; and (3) muck 

 2,000 lbs., ash 25 lbs., Thomas slag 25 lbs., calcium carbonate 100 lbs., carbo- 

 hydrate 30 lbs., inoculating soil 25 lbs. 



Satisfactory inoculation of the composts was secured with soil which had 

 been found to give strong inoculation to each of the various groups of legumes. 

 Azotohacter chroococcum was readily introducetl by using soils from Colorado 

 and North Dakota. The inoculated composts gave strong inoculation to the dif- 

 ferent groups of legumes when the latter were grown in sterilized sand cultures 

 using the composts at the rate of 2 lbs. per acre of 2,000,000 lbs. Somewhat 



