CHAPTEK III. 

 SOLUBLE SALTS IN FIELD SOILS. 



All the food of plants is taken by them in the form of 

 liquids or of gases, and hence the fertility of a soil must be 

 determined by the rate at which plant food may be dis- 

 solved in the soil water and carried to them at the time the 

 crops are growing. If the ash ingredients and the nitro- 

 gen used by plants while growing are supplied in the soil 

 water as rapidly as the crop can use them, then maximum 

 yields will be certain if the temperature and sunshine are 

 also right. 



104. Amount of Soluble Salts in Field Soils. There is a 

 very wide difference in the amount of salts dissolved in 

 soil water under different conditions. In arid regions, 

 where there is little soil leaching, the salts become in places 

 so abundant that plants are unable to grow and .alkali 

 lands are the result. In humid climates, especially where 

 the soils are sandy, the salts may be so small in amount 

 that plants starve. In the table below these differences 

 are shown for the surface foot. 



These figures show a range of total salts soluble in water 

 from 17 tons per acre foot to less than .05 tons. 



