SOIL OEGANISMS 



429 



Three modes of nitrogen fixation are tisually recognized : (1) 

 rain-water additions, (2) the action of soil organisms func- 

 tioning independently of living higher plants, and (3) the 

 influence of organisms functioning parasitieally or symbi- 

 otieally in the soil. 



236. Additions of nitrogen in rainwater. — ^Nitrogen oc- 

 curring in rainwater is generally in the nitrate and ammoni- 

 eal forms and, consequently, is readily available to plants. 

 The amounts thus brought down are quite variable, usually 

 fluctuating markedly with season and location. The follow- 

 ing table gives some of the more important findings regarding 

 the amount of nitrogen thus added to the soil in various parts 

 of the world. 



Table XCIV 





Years 



OF 



Eecord 



Rainfall 



IN 



Inches 



Pounds to the 

 AoEE A Year 



Location 



Ammo- 



NIACAL 



Nitrogen 



Nitrate 

 Nitrogen 



Harpenden, England ^ . . . . 



Garf ord, England ^ 



Flahult, Sweden ^ 



28 

 3 

 1 



2 



10 



6 



28.8 

 26.9 

 32.5 

 27.6 



23.4 

 29.3 



2.64 

 6.43 

 3.32 

 4.54 



4.02 



4.42 



11.50 



1.33 

 1.93 

 1.30 



Groningen, Holland * 



Bloemfontein and Durban, 



S. Africa^ 



Ottawa. Canada ® 



1.46 



L39 

 2.16 



Ithaca, New York ^ 



1.01 



^Russell, E. J., and Bichards, E. H., The Amount and Composition 

 of Bain Falling at BotTiamsted; Jour. Agr. Sci., Vol. IX, pp. 309-337, 

 1919. 



^Crowther, C, and Enston, A. G., The Nature, Distrihutwn and 

 Effects upon Vegetation of Atmospheric Impurities In and Near an 

 Industrial Town; Jour. Agr. Sci., Yol. IV, pp. 25-55, 1911. 



'Von Peilitzen, H., and Lugner^ I., On the Quantity of Ammonia 

 and Nitric Acid in Rainwater Collected Near Flahult, in Sweden; Jour. 

 Agr. Sci., Vol- III, pp. 311-313, 1910. 



^Hudig, J., The Amounts of Nitrogen as Ammonia and Nitric Add 



