40 RURAL CALIFORNIA 



handicaps are overcome, they closely approach the 

 recent soils in agricultural value. 



"Wherever drainage conditions are poor and there 

 is a larger amount of water passing from the surface 

 by evaporation than passes down through the soil 

 mass, there is the possibility of an accumulation of 

 soluble material or 'alkali' on the surface. The term 

 'alkali/ as ordinarily used, includes any soluble in- 

 organic salts present in sufficient quantity to be in- 

 jurious to plants. The most common materials are 

 sodium chloride or common salt, sodium sulphate or 

 Glauber's salt, and sodium carbonate or washing soda. 

 This 'alkali' is not necessarily brought into the soil 

 from some other location. It is merely a result of 

 a regrouping of the chemicals that existed in the 

 original rock, and the concentration of these com- 

 pounds in the surface soil because of excessive evapo- 

 ration. 



"If the soil has good natural drainage, any excess 

 of water will percolate through the soil and will seep 

 out to the country drainage channels, carrying with 

 it in solution, small quantities of the soluble salts. 

 In such cases, the waters evaporated from the surface 

 cannot exceed the amount that passes down through 

 the soil, and alkali accumulations cannot occur. If 

 the natural drainage conditions are not good, arti- 

 ficial drainage will be necessary if the land is to be 

 irrigated and farmed. In arid regions, the irriga- 

 tion of poorly drained lands will ultimately bring 

 about the accumulation of injurious amounts of 

 alkali. 



