THE NITROGEN CYCLE 465 



To what extent the relation is symbiotic is not known at 

 present, but it seems probable that a relation may exist 

 similar to that between leguminous plants and the nitrogen- 

 gathering bacteria in their nodules. 



384. Nitrogen fixation and denitrification antagonistic. 

 — Nitrogen fixation and denitrification are reverse pro- 

 cesses. The former is, for most bacteria, favored by 

 an abundant supply of air and a moderately high tempera- 

 ture. Thus, at 75° F. fixation was rapid, at 59° F. it was 

 decreased, and at 44° F. there was no fixation. Denitri- 

 fication is favored by a somewhat limited supply of 

 oxygen. 



There is no reason to believe that the practical impor- 

 tance of nitrogen fixation without legumes is equal, under 

 the most favorable conditions, to that with legumes. 

 A further knowledge of the organisms effecting fixation 

 and of their habits will doubtless make possible a greater 

 utilization of their powers to supplement the use of leg- 

 umes as a source of combined nitrogen in the soil. 



TREATMENT OF SOILS WITH VOLATILE ANTISEPTICS AND 

 WITH HEAT 



Attention was first drawn to the effects of carbon bisul- 

 fide on the soil in a paper by Girard l and one by Oberlin 2 

 which appeared in 1894. Girard noticed that soil treated 

 with carbon disulfide for the purpose of combating a para- 

 sitic disease of sugar-beet was more productive than it 



1 Girard, A. Recherches sur l'Augmentation des Recoltes 

 par 1' Injection dans le Sol du Sulfure de Carbone a Doses Mas- 

 sives. Bui. Soc. Nationale d'Agric., Tome 54, p. 356. 1894. 



2 Oberlin. Bodenmiidigkeit und Schwefelkohlenstoff. Mainz, 

 1894. 



2h 



