430 NATURE AND PROPERTIES OF SOILS 



Apparently the ammoniacal 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 considerably larger than those from any other station. 

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

 that on the average about 4y 2 pounds of ammoniacal and iy 2 

 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 Uithuizer-Meeden, Gronigen; Jour. Agr. 

 Sci., Vol. IV, pp. 260-269, 1912. 



5 Juritz, C. P., Chemical Composition of Rain in the Union of South 

 Africa; S. Africa Jour. Sci., Vol. 10, pp. 170-193, 1914. 



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

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



T Wilson, B. D., Nitrogen in the Rainwater at Ithaca, New York; 

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



