POOR CROPS AND HOW TO GET BETTER ONES 133 



How to know alkali soils. Alkali soils are usually 

 known by the fact that they have a white (sometimes 

 brown or black) crust of salts on the surface in the dry 

 season, or when sunny weather comes after rains. This 

 is because the soil water, evaporating at the surface, 

 brings the salts up with it. 



Sometimes this crust tastes strongly of common salt, but 

 mostly it is also bitter (the taste of Glauber's and Epsom salts), 

 and when dark-colored it tastes of salsoda also. In the latter 

 case farmers speak of " black alkali/ 7 otherwise of " white 

 alkali." And they know that black alkali makes it more 

 difficult to grow crops than when the alkali is white ; that is, 

 when it consists mainly of common salt and Glauber's salt, 

 with little or no salsoda or carbonate of soda. 



The three salts mentioned are useless or injurious to vege- 

 tation; the land would be better without them. But at the 

 same time with these useless substances, the scarcity of rain 

 has left in the alkali soils also the whole of the plant food set 

 free by the weathering. When reclaimed by washing out 

 the noxious salts, alkali soils are therefore highly and last- 

 ingly productive. 



Getting the alkali out of soils. To get the alkali out 

 of soils we have only to do what nature does in regions 

 of abundant rains; wash it through the soils into the 

 streams, or underground drainage. 



\ t When the jsoils^are very sandy, flooding with irrigation 

 water quickly does this; but usually it would take a great 

 deal of time, especially in ^black alkali lands, where water 



k% soaks down very slowly. We may then underdrain the land 



