SOILS FERTILIZERS. 319 



When sugar was added in varying amounts (20 to SO gin. per kilogram of 

 soli) it was found that the hirgest fixation of nitrogen per gram of sugar 

 occurred in tlie soil to which sugar was added at the 20 gm. rate, the amount 

 of fixation heing on an average 10 mg. of nitrogen to each gram of sugar added. 

 Practically the same rate of fixation was shown by pure cultures of Azotobacter. 

 When the amounts of sugar were increased to 40, 60, and 80 gm. per kilogram 

 of soil thei'e was an absolute increase in fixation, but a steady decrease per 

 grain of sugar. Beyond SO gm. there was a rapid absolute decrease. Frac- 

 tional weekly applications of sugar of 2 gra. each for 8 weeks gave aljout the 

 same fixation as 20 gm. in one application. With 2 gm. of sugar in IS weekly 

 applications thei'e was a decided decline in fixation, and the same was true in 

 case of repeated applications of somewhat stronger sugar solutions. When, 

 however, 18 separate applications of 20 gm. each of sugar were made there was 

 a large absolute increase in fixation of nitrogen, amounting to 0.8 gm. per kilo- 

 gram of soil. 



There \a as a distinct loss of nitrogen when sugar was applied in March while 

 the temperature of the soil out of doors was still low. Active fixation set up, 

 h()^^•ever, when the soil was brought into a warm room. 



The application of lime not only did not increase fixation of nitrogen, but in 

 some cases actually lowered it. The injurious effect of potassium salts, espe- 

 cially the chlorid, was quite pronoiuiced. On the other hand, applications of 

 phosphoric acid very greatly promoted fixation. Carbon bisulphid did not 

 increase fixation, and in many cases reduced it somewhat. Fixation was decid- 

 edly increased by applications of iron sulphate. 



In pot experiments with applications of molasses as a cheap source of car- 

 bonaceous food for the nitrogen-fixing bacteria there was a decided loss of nitro- 

 gen, thought to be due to the fact that the molasses contained nitrogen com- 

 pounds which were easily decomposed by the organisms which fed upon this 

 nitrogen rather than upon the free nitrogen of the air. Organic matter of veg- 

 etable origin was not found in these experiments to be a good source of carbona- 

 ceous food for the nitrogen-fixing organisms. 



In i)ot experiments with biickwheat, oats, and other croi)S there was a decided 

 decrease in yield the first year when the sugar was applied in March in the 

 open. The following year, however, there was an increased fixation of nitro- 

 gen and a marked improvement in growth and yield of crop on the soil to which 

 sugar had been applied the jirevious fall, indicating that the nitrogenous matter 

 elaborated by the nitrogen-fixing organisms is readily assimilated by higher 

 plants, and that there was a close and direct correlation between fixation of 

 nitrogen, nitrification, and increase of yield. 



Soil inoculation by means of pure cultures, J. Vandebghem (BoL Min. 

 Fomrnio [Peru], Jf (1906), No. 12, pp. 9-12). — Inoculation experiments with 

 alfalfa are briefly reported. Inoculation was ineffective on soil which had pre- 

 viously grown a leguminous crop. 



On the action of the micro-organisms in rendering the potash of leucite 

 in soils available to higher plants, vS. de Grazia and G. Camiola {iitaz. Sper. 

 Afir. Hal., .i9 {19(iG), No. 9, pp. 829-8/fO ; abs. in Chem. Zentbl, 1907, I. No. 19, 

 p. I.',')!; Jour. Chem. Soc. [London], 92 (1907), No. 538, II, p. 6^1).— In investi- 

 gations on leucite, similar to those on insoluble phosphates already referred to 

 (E. S. R., 18, p. 920), it was found that the amount of potash in the soil solu- 

 tion was greater when micro-organisms were present than when they were 

 absent. It is suggested that the organisms absorlied and assimilated the potash 

 and so made it more readily available for higher plants. 



Experiments on the lasting effect of green manure nitrogen on light, 

 sandy soils, C. von Seelhobst {Mitt. Dent. Landtc. Qesell, 22 {1907), No. IJ,, 



