534 



EXPERIMENT STATION RECORD. 



The author claims that chemical soil analysis is of the highest value and may be 

 safely used as a guide in determining whether a soil is so poor that it is entirely 

 dependent upon the application of plant food for the production of crops, or only 

 requires the return of the i)lant food removed by crops, or is so fertile that it may be 

 cropped for a series of years without requiring any .addition of fertilizing material. 

 The following classific'ation of soils, based on chemical composition, is given: 



Classification of soils based on chemical composition. 



a Soluble in cold hydrochloric acid. 



As regards humus content the author classifies soils as follows: With to 2 per cent 

 of humus in the air-dry fine earth, soil is considered slightly deficient or poor in 

 humus; 2 to 3 per cent, of medium humus content; 3to 5, of good humus content; 5to 8, 

 well supplied with humus (humous); 8 to 10, very well supplied with humus (very 

 humous) ; 10 to 15, rich in humus; 15 to 20, very rich in humus, approaching moor soil, 

 and over 20 per cent, moorlike or peaty. 



Humus substances as a nitrogenous constituent of the soil, A. Doyarenko 

 {Izv. Moscow SeM. Klioz. Inst. [Ann. Inst. Ayron. Moscou'], 6 {1900), No. 4, pp. 440- 

 483). — The object was to ascertain the way in which humic acids absorb nitrogen, and 

 in what form tlie latter is retained after absorption. As a preliminary study the 

 chemical nature of the nitrogenous constituents of the humic acids of the soil was 

 investigated. For the latter purpose the humic acids of 7 different soils was extracted 

 with a 10 per cent solution of sodium carbonate. In order to remove the slimy 

 impurities which always accompany the extract the latter was filtered through a 

 porous clay filter. In the pure humic acid the total nitrogen was determined by 

 the Kjeldahl method, the amido-acid nitrogen by Bohmer's method, the amid 

 nitrogen by Schultze's method, and lastly the ammoniacal nitrogen. The analyses 

 gave the following results: Amido-acid nitrogen, 22.01 to 70.27 per cent of the total 

 nitrogen; amid nitrogen, 5.47 to 12.13 per cent of the total nitrogen. 



For the study of the ajjsorption of nitrogen by humic acid, 2 series of experiments 



