WATER SOILS. 677 



upon the decompositiou of the organic matter of the soil and upon the 

 movement and distribution of the sohible constituents of the soil. 



The injury caused by the leaching of the soil by long periods of rain- 

 fall and by concentration of soluble salts at the surface of the soil by 

 long periods of drought are noted, and the intiuence of plant cover in 

 mitigating this are pointed out. 



The distribution of the salts in alkali soils, E. W. HiLaARD 

 and E. H. LoucTHKiDdE {California Sta. h'pt. lso.',^pp. 37-69, (Jgms.8). — 

 The main jjoiuts of this article have already been published,^ the 

 detailed data being given here in tables and diagrams. The article is 

 based on observations and experiments at the Tulare Substation. The 

 topics discussed are natural conditions of the land, the questions to be 

 solved, the effect of rainfall and irrigation, effect of application of 

 gypsum, effect of cropping, percentage composition and total amounts 

 of salts in the different soils, black and white alkali, counteracting 

 evaporation, and Australian saltbush on alkali soils. 



It is shown that there is an accumulation of alkali in the soil at a 

 depth of about 3 ft., due to the fact that rainfall in regions where 

 alkali occurs rarelj' wets the soil to a greater depth than this. Where 

 irrigation is practiced the evaporation of the water causes the alkali 

 to rise toward the surface. The bulk of the alkali salts is therefore 

 accumulated within easy reach of the surface and of underdrains, and 

 if once removed there is little danger that a sufficient amount of it to 

 do any harm will again come from below. 



" [Applicatious of 1^ tous per acre of gypsum were made during 1894 and 1895 to an 

 alkali spot] with the result that while iu 1893 scarcely a blade of the barley sown 

 matured seed, iu 1891 (a very dry season) about half the land bore barley hay at the 

 rate of a ton per acre, growing 2 ft. high, and maturing seed where allowed to 

 stand. In 1895 the reclamation had progressed nearly 100 ft. farther east in the 

 direction of the original spot. The barley sown refused to germinate only within 

 the limits of that spot, but on the rest of the tract was 2 ft. high in March, and 4 

 ft. in May, the land yieldiug hay at the rate of 2+ tons per acre. The line between 

 the reclaimed and unreclaimed land Avas very sharp, so that the luxuriant crop and 

 the bare surface were at times within 5 ft. of each other, with a narrow band of 

 etiolated grain between." 



An examination of the soil so treated indicates "that in a sandy loam, 

 in which the upi)er 3 in. contain, at the end of the dry season, not over 

 1.4 per cent of alkali, consisting chiefly of Glauber's salt (sulphate of 

 soda), barley can be made to yield a fair crop." 



"It is evident, from the facts given, tliat lor barley the limit of toleration consist- 

 ent with a full hay croji, under otherwise favorable conditions, and with salts con- 

 sisting of not over one-half of carbonate of soda, lies somewhere between 25,500 and 

 32,000 11)8. per acre, in round numbers, within the lirst 4 ft. of soil and subsoil; 

 always provided, that the layer so limite<l contains substantially all the salts likely 

 to come within reach of surface evaporation. Expressed in percentages of the soil 

 and subsoil mass itself, this indicates, respectively, 0.159 and 0.203. . . . 



'U. S. Dept. Agr., Office of Experiment Stations Bui. 30, p. 66 (E. S. R., 7, p. 173) ; 

 U. S. Dept. Agr. Yearbook 1895, p. 103. 



