430 NATURE AND PROPERTIES OF SOILS 



Apparently the ammoniaeal nitrogen is always consider- 

 ably larger in amount than that in the nitrate form. It is 

 also noticeable that while the nitrate nitrogen is about the 

 same for every station, the nitrogen in the form of ammonia 

 shows wide variations. The quantities at Ithaca, New York, 

 are consiHerably larger than those from any other station. 

 Considering the figures as a whole, it seems fair to assume 

 that on the average about 4% pounds of ammoniaeal and 1% 

 pounds of nitrate nitrogen fall on every acre of soil yearly 

 in rainwater. Assuming that all of this nitrogen passes into 

 the soil, an average gain to the acre of 6 pounds of nitrogen 

 may be expected. 



It is interesting at this point to compare such a gain with 

 the annual loss of nitrogen from the soil. The removal of 

 nitrogen from the Cornell lysimeter soils (see par, 163), 

 through drainage and cropping combined, amounted to 69.0, 

 77.8 and 56.9 pounds yearly to the acre, respectively, for a 

 bare soil, one carrying a standard rotation, and one continu- 

 ously in grass. While a gain of 6 pounds to the acre yearly 

 seems rather insignificant in comparison to these figures, such 

 an addition is of considerable importance over a period of 

 years, and has had much to do with the accumulation of the 

 nitrogen of our arable soils. Such a gain is equivalent in a 

 practical way to the addition of about 40 pounds of commer- 

 cial sodium nitrate to the acre yearly. 



237. Acquisition of nitrogen by free-fixing organisms. — 

 While it has long been known that the soil contains a great 

 variety of organisms, it is only in recent years that it has been 



in the Rainwater Collected at Uithuiser-Meeden, Gronigen; Jour. Agr. 

 Sei, Vol. lY, pp. 260-269, 1912. 



** Juritz, C. F., Chemical Composition of Main in the Union of South 

 Africa; B. Africa Joiir. Sci., Vol. 10, pp. 170-193, 1914. 



"Shutt, F. T., and Dorrance, R., The Nitrogen Compounds of Bain 

 and Snow; Proc. and Trans. Roy. Soe. Canada, Vol. XI, No. 3, pp. 63-71, 

 1917. 



^Wilson, B. D., Nitrogen in the Bainwater at Ithaca, New Yorh; 

 Soil Sci, Vol. XI, No. 2, pp. 101-110, 1921. 



