MANURES 319 



surface when the salts have accumulated there in time 

 of drought. While this may aid in the work of ameliora- 

 tion, it is not a final solution of the difficulty. (3) Wash- 

 ing the alkali from the land by turning on a rapidly 

 moving body of water, when the alkali is encrusted on 

 the surface of the soil, has been tried, but with poor suc- 

 cess, as the alkali is largely carried into the soil, instead 

 of being removed by the water passing over the surface 

 of the land. 



185. Alkali spots. In semi-arid regions, small areas 

 of alkali are frequently found, varying from a few square 

 yards to several acres in size. The quantities of alkali 

 in these are usually not sufficient to prevent the growth 

 of crops in years of good rainfall, but in periods of 

 drought the concentration of the salts and the compact 

 condition they tend to produce combine to injure the 

 crop. The methods already mentioned for treating alkali 

 land are of service on these small areas, and, in addition, 

 the plowing under of fresh farm manure has been found 

 to improve their productiveness. This, with surface 

 drainage, deep tillage and good cultivation, to prevent 

 the soil from drying out, will usually remedy the diffi- 

 culty. Frequently these spots become highly productive 

 under proper treatment. 



VII. MANURES 



A manure is any solid substance added to the soil to 

 make it more productive. This it may do: (1) By im- 

 proving the physical condition of the soil, as usually 

 results from the application of lime and the incorporation 



