320 EXPERIMENT STATION RECORD. [Vol. 41 



isms of the soil. Taking the sum of nitrates and ammonia, there was the great- 

 est action in the i>resence of lime on the untreated soil, but the reverse was true 

 in most cases for the treated pots. 



The two soils showed as marked differences in their behavior as did the dif- 

 ferent treatments. The more acid soil was much more active, probably because 

 of greater content of organic matter and a more al)un(lant flora. 



The relation of the lime requirements of soils to their retention of am- 

 monia, L. P. Howard (Soil Sci., 6 (1918), No. 6, pp. 405-4ii ) .—Experiments 

 conducted at the Rhode Island Experiment Station on the determination of the 

 lime requirement of soils are reported in whicli soils were treated with ammo- 

 nium hydroxid, the excess ammonia evaporated off at the temperature of boiling 

 water, and the retained ammonia estimated. 



Within reasonable limits the requirement based upon this retention was 

 independent of (1) concentration of ammonia added, (2) time of contact, and 

 (3) temperature during evaporation. The requirement was about 25 per cent 

 lower than that indicated by the Yeitch method. Aeration in the presence of 

 sodium carbonate for IS hours (300 liters of air per hour) was sufficient to 

 remove completely from 50 to 75 mg. of ammonia from the soil. Sodium, 

 ammonium, and potassium from solutions of their hydroxids and carbonates 

 were retained in practically equivalent amounts. It is believed that the ammo- 

 nia retained is held chemically by a neutralization of either free acids, acid 

 organic compounds, or acid salts, while physical absorption is largely prevented. 

 The lime requirement based upon the ammonia retention agreed in general with 

 field observations, to the extent that soils needing the most lime showed the 

 greatest lime requirement. 



Toxicity of " alkali " salts, T. M. Singh (Soil Sci., 6 {1918), No. 6, pp. 463- 

 477). — Studies conducted at the Oregon Experiment Station are reported to de- 

 termine (1) the toxic points of sodium chlorid, nitrate, carbonate, and sul- 

 phate on wheat and peas, (2) the toxic point of a combination of alkali salts 

 in field soils on Avheat and peas, and (3) the effect of sodium chlorid, nitrate, 

 carbonate, and sulphate upon ammoniflcation, nitrification, and nitrogen fixa- 

 tion. The soil used was a productive heavy silt loam. 



It was found that in order of toxicity the salts ranked as follows : Sodium 

 chlorid, nitrate, carbonate, and sulphate. The percentage of the anion and not 

 the cation was the determining factor. Small amounts of each of the different 

 salts used stimulated both crop growth and bacterial activities. This amount 

 varied with tlie crop grown, and the concentrations at which stimulation took 

 place bore the same relationship to each other as did their toxicity points. 



Sodium chlorid became toxic to both ammoniflcation and nitrogen fixation 

 at a concentration of 0.01 per cent. The toxic point for wheat was 0.4 and for 

 field peas 0.2 per cent. 



Sodium nitrate became toxic to ammonification at a concentration of 0.01 per 

 cent and to nitrogen fixation above 0.4 per cent. Small concentrations of 

 sodium nitrate proved toxic to nitrification, but at a concentration of 0.4 per 

 cent a marked stimulation took place. The toxic points for wheat and for peas 

 were 0.8 and O.G per cent, respectively. 



Sodium carbonate was toxic to ammonification at a concentration of 0.02 per 

 cent, to nitrification at 0.8 per cent, and to nitrogen fixation at 0.01 per cent. 

 For wheat the toxic point was 1 per cent and for peas 0.6 per cent. 



Sodium sulphate proved to be the least toxic of all the salts. Neither am- 

 monification nor nitrogen fixation was inhibited to any extent at concentrations 

 up to 2 per cent and peas up to between 1 and 2 per cent. 



The toxicity point as found when salts were used in combination, as under 

 field conditions, checked very closely with the points found when the individual 



