88 Report S.A.A. Advaxcemknt of Scienck. 



cunistances, the suitability of soils foi' cultivating oeitaiii ki]i(ls of crops 

 has to be considered, a more complete and detailed discrimination be- 

 comes indispensable. 



Hilgard (Soils, their Formation, Properties, Composition, <i'c., 1906, 

 p. 84) proposes the classification given below : — 



Percentage 

 uf Clay. 

 Heavy clay soils ... ... ... ... 35 and over 



Clay soils 25 to 35 



Clay loams ... ... ... ... ... 15 ,, 25 



8andy loams ... ... ... ... 10 ,, 15 



Ordinary sandy lands ... ... ... 3 ,, 10 



Very sandy soils ... ... ... ... i ,, 3 



Professor Whitney, chief of the Bureau of 8oils of the United 

 "States Department of Agriculture, puts forward no less than si.xteen 

 ■classes of soil, viz., stony hjam, gravel, gravelly loam, dune sand, sand, 

 fine sand, sandy loam, fine sandy loam, loam, shale loam, silt loam, 

 clay loam, clay, adobe, meadow, and muck and swamp.* 



Snyder (The Chemistry of Soils and Fertilisers, 1899, p. 24) refers 

 to "sandy," "clay" and "loam" as the terms "used to designate the 

 prevailing chaiacter of the soil." Sandy soils he classes as tliose con- 

 taining 90 per cent, or more of pure sanfl. He mentions, furthei', loajn 

 isoils— i.e. mi.xture of sand and clay ; if clay predominates it is a clay 

 loam ; if sand, a sand}' loam. Dealing with the preference of certain 

 crops for particular classes of soil, he supplements his classification by 

 iuentioning the classes <jf soil which in a large number of cases and 

 under average conditions {e.<j. normal supply of plant food and nu 

 average rainfall) have proved to be satisfactory crop producer^. 



The better class of potato soils, according to him, ai-e those wjiich 

 contain about 60 per cent, of medium sand, 20 to 25 per cent, of silt. 

 and about 5 per cent, of clay. For fruit-growing purposes he recom- 

 juends soils containing from 10 to 15 pei- cent, of clay, and not more 

 than 40 per cent, of sand. He looks upon those as the strongest corn 

 soils which contain from 40 to 45 per cent, of mecHum and fine sand, 

 and about \^) per cent, of clay. Good grass and general grain soils 

 •should contain about 15 per cent, of clay and 60 per cent, of silt. For 

 wheat production he discriminates between three classes of soils : those 

 of the first class contain from 30 to 50 per cent, of clay : those oi the 

 second, about 20 per cent, of sand, 50 per cent, of silt, and from 20 to 

 30 per cent, of clay ; to the third class are assigned those soils which 

 are composed mainly of silt, containing usually 75 per cent, and from 

 10 to 15 per cent, of clay. 



* In tlie 1906 Soil Survey FieM-liook issued by tlie Fiiited States Depavt- 

 iiieut of Ajiriculture, the following eleven classes are eiiunierate<l under the 

 scheme of classilicatiou hased on mechanical comjjosition of soils— coarse sand, 

 iiie<linni sand, line sand, sandy loam, tine sandy li>a)ii, loam, silt loam, clay 

 oam, sandy (day, silt clay and clay (pji, 17 and IS). 



