1919] SOILS — FERTILIZERS. 815 



Of the practice of sewage sludge pressing to obtain fertilizer material, fuel, etc. 

 Dewatering sewage sludge by filter pressing with the plate type of press has 

 been brought to a point where its efficiency and cost can be closely predicted. 

 With fresh settled or precipitated sludge, the addition of from 0.5 to 3 per cent 

 of lime, and a pressure of 70 or 80 lbs. per square inch, a firm, satisfactory cake 

 can be produced. 



Commercial oxidation of ammonia to nitric acid, C. I^. Parsons {Jour. 

 Indus, and Engin. (Jhem., 11 (1919), No. 6, pp. 541-552, figs. 13; abs. in Chem. 

 and Metall. Engin., 20 {1919), No. 10, pp. 502, 503, fig. i).— This is a review of 

 recent progress made in the oxidation of ammonia, together with a more de- 

 tailed account of the investigational work which led to the development of 

 the experimental plant built at Syracuse, N'. Y., by the U. S. Bureau of Mines 

 in cooperation with a coniniercia] concern. 



Further contribution regarding the physiological action of ammonium salts 

 on plants, II, H. G. Soderbaum {Meddel. Centralanst. Forsoksr. Jordbruksom- 

 rddet. No. 17S {1918), pp. 12, fig. 1; also in K. Landtbr. Akad. Handl. och Tidskr., 

 57 {1918), No. 7-8, pp. 513-521, fig. 1; abs. in Chem. Abs., 13 {1919), No. 10, p. 

 1120). — Further pot experiments (E. S. R., 38, p. 121) are reported to deter- 

 mine the limits of the harmful effect of ammonium sulphate and sodium ni- 

 trate, alone and mixed, on oats, barley, vetch, and Italian rye grass on sand 

 soil. 



It was found that for oats the limiting amount of ammonia nitrogen was be- 

 tween 142 and 178 lbs. per acre, and for barley between 36 and 53 Ibf^. per 

 acre. With rye grass no harmful effects were observed up to 178 lbs. per acre. 

 With vetch the effect of ammonium sulphate was most pronounced, the smallest 

 amounts used in any pot decreasing the plant growth. Vetch was also sensi- 

 tive to sodium nitrate, but in less degree than to ammonium sulphate. 



An afterwar fertilizer, ammonium nitrate, I^. Malpeaux {Vie Agr. et Rurale, 

 8 {1918), No. Jf5, pp. 335-339). — Tests of ammonium nitrate and ammonium siil- 

 phate on three different soils showed that the ammoniacal nitrogen of the am- 

 monium nitrate is not so well retained by the soil as that of the sulphate, but 

 that the nitrate contents of the soils were increased more by the ammonium 

 nitrate. Annnonium nitrate gave about the same results in this respect as 

 sodium nitrate. 



In pot experiments with oats the best total results were obtained with am- 

 monium sulphate. Ammonium nitrate gave slightly better results than sodium 

 nitrate, although the weight of grain obtained with the latter was somewhat 

 greater. 



Plat experiments with oats, .sugar beets, and potatoes using sodium nitrate, 

 calcium nitrate, ammonium nitrate, ammonium sulphate, and cyanamid showed 

 that calcium nitrate gave the best results for oats, followed closely by sodium 

 nitrate. Ammonium nitrate and cyanamid gave about the same results with 

 oats, which were only slightly less than with the two better fertilizers. All the 

 fertilizers gave a marked increase over unfertilized soils. Ammonium nitrate 

 gave the best results with sugar beets, but marked increases were obtained in 

 all cases. With potatoes calcium nitrate gave the best results, which, however, 

 were only slightly superior to those obtained with sodium nitrate and am- 

 monium nitrate. 



It is concluded that ammonium nitrate is a very active fertilizer and should 

 be classed with sodium nitrate and ammonium sulphate in this respect. 



It is further concluded from these experiments that the choice of a nitroge- 

 nous fertilizer should be governed by price, availability, and nature of the .soil. 



Influence of dicyandiamid on plant growth, E. .Johnson {Tidskr, Kemi, 15 

 {1918), pp. 349-367, 369-393; abs. in Chem. Abs., 13 {1919), No. 12, p. 1354).— 



