82 RELATIONS OF SOIL TO WATER 



These soils were in different localities ; the results do not 

 therefore show how different soils behave with the same 

 rainfall, but rather the amount of water found in soils specially 

 suited to certain crops in a season of fair average production. 

 The soils best suited for market-garden purposes, or for the 

 growth of the bright yellow tobacco used for cigarettes, thus 

 only held from 5-11 per cent, of water; the shipping tobacco 

 soil 1 2-1 8 per cent. ; and the pasture soil (used also for the 

 coarsest tobacco) 18-23 per cent. Each of these conditions 

 was especially suited for the purpose of the particular crop 

 cultivated. 



A detailed account of the physical texture and water- 

 holding power of soils producing distinct varieties of tobacco 

 is given by Whitney in a later Bulletin (Soils, No. n). The 

 delicate, elastic leaf, used for cigar wrappers, and the bright 

 yellow tobacco already referred to, are only produced on 

 sandy soils holding but little water. The thicker, coarser 

 leaf, with which is associated a much larger return per acre, 

 is grown on soils containing a more or less considerable 

 proportion of clay, and holding a much larger quantity of 

 water. 



- According to Whitney's observations, the water contents 

 may rise to one-quarter more than the normal amount, or fall 

 to one-quarter below it, without seriously disturbing the 

 characteristic quality of the soil. With a greater diminution 

 of water drought will be felt, and with a permanently greater 

 increase in the water contents the crop will be injured. 



An attempt is being made in the United States to obtain 

 daily records of the water contents of typical soils by measur- 

 ing the resistance to an electric current passing between two 

 electrodes sunk in the soil. 



