18 EXPERTMEXT STATIOX RECORD. [Vol.43 



The rainfall regime of Tunis, (J. Ginestous (Dir. Gen. Af/r., Com. et Colon. 

 [Tunis], Bill., 22 (1918), No. 94, PP- 51-80, pis. 5).— The amount and monthly 

 and seasonal distrihution of rainfall during the year ended November 30, 1918, 

 are shown in tables and charts, and the outstanding facts are briefly discussed. 



The winter rainfall (December to February) was deficient. The .spring 

 rainfall was above the normal and very favorable for crop growth. The 

 suinnier was almost rainless except the tirst part of July, The autumn rainfall 

 was slightly below normal. 



SOILS— FERTILIZERS. 



The organic matter of the soil: A study of the nitrogen distribution in 

 different soil types, C. A. Moerow (Thesis, Univ. Minn., 1918, pp. 79). — A his- 

 torical review of the subject is given, and studies of the nitrogen distribution 

 in several different substances and soil types using the Van Slyke method 

 are reported, including fibrin hydrolyzed in the presence of a mineral subsoil, 

 a calcareous black grass peat, an acid sphagnum-covered peat hydrolyzed alone 

 in the presence of a mineral subsoil and in the presence of stannous chlorid, 

 an acid muck soil, seven samples of mineral surface soil, and extracts of a 

 sphagnum-covered peat and of a calcareous black grass peat soluble in 1 per 

 cent of hydrochloric acid, 4 per cent sodium hydroxid but precipitated by acid, 

 and 4 per cent sodium hydroxid and not precipitated by acid. The seven 

 mineral soils included Fargo clay loam, Fargo silt loam, Carrington silt loam, 

 Hempstead silt loam, prairie-covered loess, and forest-covered loess. The fol- 

 lowing conclusions are drawn : 



" The figures for the ammonia nitrogen in a protein analysis are not appre- 

 ciably changed when the hydrolysis is carried out in the pi'esence of an ignited 

 mineral soil equal to 20 times the weight of the protein material. The ' humin ' 

 nitrogen is greatly increased by the addition of ignited mineral soil. It was 

 shown that histidin nitrogen can not account for this increase, neither is it 

 due to the presence of carbohydrates, since the soil lost all its organic matter 

 on ignition. . . . Since practically all mineral soils give furfural on treat- 

 ment with acid, it is very likely that a very considerable amount of the total 

 humin nitrogen found is due to the presence of carbohydrates in the soil, which 

 give rise to furfural during hydrolysis. This may combine with certain of the 

 nitrogenous compounds and cause an increase in the humin nitrogen, as well 

 as adsorb or occlude nitrogenous compounds in the humin formed from fur- 

 fural by polymerization. 



" This investigation of the distribution of organic nitrogen in the soil indi- 

 cates a new fraction, the nature of which has not been previously recognized. 

 This is the fraction of nitrogen removed from a colorless solution by calcium, 

 iron, and aluminum hydroxids on the addition of calcium hydroxid. The 

 nitrogen retained in this fraction must consist almost entirely of nonprotein 

 material, since the organic sul)stances in this precipitate have been shown to 

 be colorless organic compounds adsorbed by or combined with the metallic 

 hydroxids. This fraction has been reported as nitrogen precipitated by calcium 

 hydroxid. The true humin nitrogen remains in the residual soil after hy- 

 drolysis, but in addition nonhumiu nitrogenous compounds must also be re- 

 tained in this fraction. The strength and volume of the hydrochloric acid 

 used in hydrolysis has little effect on the nitrogen distribution of the hy- 

 drolysate, provided acid as strong as constant boiling acid is used in the 

 proportion of at least two parts of acid to one of soil. Results gained from 

 a study of different soils indicate that the organic nitrogen dissolves during 



