MOVEMENTS OF SALTS IN SOILS. 113 



LOSS OF PLANT FOOD IN SURFACE DRAINAGE. 



When the methods of cultivation are such asi to intensify the 

 concentration of water-soluble salts at the immediate surface, 

 and where the texture of the soil, the character of the rainfall 

 and the topography are such as to cause frequent surface drain- 

 :itiv, there must be, of necessity, heavy losses of soil fertility as 

 the result of such conditions. 



It was showni, from the data of the table, p. 64, that through 

 capillary concentration during 15 to 20 days, 60 per cent, of 

 all nitrates contained in the surface foot may be brought into 

 the surface 2 inches, and much the larger share of this 60 per 

 cent, is carried to or very near the immediate surface. At the 

 end of less than 5 days the surface 2 inches of soil contained 

 127.93 parts per million of dry soil, while the 10 to 12 inch 

 level contained but 2.61 parts. Rapid movements like these 

 under consideration are liable to occur whenever very drying 

 weather follows a rainfall which leaves the surface 12 inches of 

 soil nearly saturated with water, and with it there must be a 

 concentration of nitric acid and lime at the immediate surface, 

 with other salts also. 



Where the granular structure of the soil is feeble, as it is so 

 often in the South, heavy rains, and even very moderate ones, 

 so puddle the immediate surface that the water does not enter 

 the soil readily but quickly flows to the lowest places, carrying 

 with it the soluble salts which have been concentrated at the 

 surface and, if the fields are furrowed, as is shown in the two 

 engravings, much of the rainfall is liable to pass away in sur- 

 face drainage and with it whatever of salts have been dissolved. 



Deeper plowing, which incorporates more of organic matter, 

 and flat cultivation are two essential conditions which will very 

 materially lessen these bad effects. 

 8 



