722 EXPERIMENT STATION" RECORD. [Vol. 40 



The effect of prolonged growing 1 of alfalfa on the nitrogen content of the 

 soil, C. O. Swanson (Jour. Amer. Soc. Agron., 9 (1917), Xo. 7, pp. 305-31$).— 

 This paper, a contribution from the Kansas Experiment Station, forms a 

 partial report on work still in progress, the essential features of which have 

 already been noted from another source (E. S. R., 40, p. 319). Summarizing 

 briefly, it may be stated that the observations show that on the whole the grow- 

 ing of alfalfa has not added to the amount of nitrogen present in the soil except 

 in a few instances in the semiarid portion of the State, and that all that the 

 alfalfa accomplished was to prevent further losses of nitrogen, that is, to main- 

 tain an equilibrium. 



Influence of salts on the nitric-nitrogen accumulation in the soil, J. E. 

 Greaves, E. G. Carter, and H. C. Goldthorpe (Jour. Agr. Research [U. S.], 16 

 (1919), No. .',. pp. 107-135, figs. 5).— In these investigations, made at the Utah 

 Experiment Station, "the soil used was a sandy loam very high in acid-soluble 

 constituents, but the water-soluble constituents were not excessive. The calcium 

 and magnesium contents were very high and mainly in the form of the carbon- 

 ate The soil was well supplied with phosphorus and potassium, and there was 

 a fairly large quantity of iron present. In fact, all of the elements of plant 

 food were present in abundance, with the exception of nitrogen, which was low. 

 The soil was very productive, and previous work had shown the ammonifying 

 and nitrifying powers of the soil to be about the average for the soils of the 

 arid regions. The nitrogen-fixing powers of the soil were above the average, and 

 previous work had shown it to have an intensely Interesting bacterial flora." 



To 100 .mn. portions of the soil (air-dried in the dark i '2 gm. of dried blood 

 and the salts to be tested wen' added, the moisture content made up to 20 per 

 cent, and the whole incubated at 28 to 30° C. for 21 days. At the cud of 

 this time the nitric nitrogen was determined. The salts tested Included the 

 chlorids, nitrates, sulphates, and carbonates of sodium, potassium, calcium, 

 magnesium, manganese, and iron. The proportion of salts used varied from 

 nothing to several thousand parts per million of soil. 



Summarizing tic results the authors conclude that the toxicity of the salts 

 as regards nitrification is determined by the specific salt and not by the electro- 

 negative ion, and that "with the exceptions of the manganous Chlorld and sul- 

 phate and the chlorids of iron and sodium, the salts tested all become toxic at a 

 lower concentration to the nitriliers than to the ammonifiers. The quantity of 

 a salt which can he applied to a soil without decreasing the nitric-nitrogen ac- 

 cumulation in the soil varies with the salt, and for the soil under investigation 

 it is in the order of decreasing toxicity of the salts as follows: Sodium sul- 

 phate, sodium carbonate, calcium carbonate, potassium sulphate, potassium car- 

 bonate, ferric nitrate, sodium nitrate, magnesium sulphate, ferric sulphate, cal- 

 cium nitrate, potassium nitrate, potassium chlorld, magnesium nitrate, man- 

 ganoua carbonate, manganoua eWorld, manganous sulphate, ferric carbonate, 

 magnesium chlorld, manganous nitrate, ferric chlorld, magnesium carbonate. 

 sodium cblorid, calcium chlorid, and calcium sulphate. It is not necessarily 

 those compounds which become toxic in the lowest concentrations which are 

 most toxic in higher concentrations, as the toxicity of some salts increases more 

 rapidly than the toxicity of others." 



Osmotic pressure appeared to play only a minor part in retarding bacterial 

 activity. 



"The common soil 'alkalis,' calcium chlorid, sodium sulphate, sodium car- 

 bonate, and the less common one, calcium nitrate, are very toxic to the nitrify- 

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

 the nitric-nitrogen accumulation in such a soil." All of the Baits except sodium 

 sulphate, sodium carbonate, calcium carbonate, potassium sulphate, potassium 



