TILLING THE SOIL 



37 



The following table shows the quantity of gypsum required to neutralize 

 sodium carbonate in an acre-foot of soil : — 



» An acre-foot of soil weighs 4,000,000 pounds. 



Very often the black alkali is accompanied by other soluble salts, 

 and the change in kind of salt brought about by the gypsum leaves 

 more white alkali than plants will stand. The economic use of gypsum 

 is therefore restricted to localities having only small amounts of total 

 soluble salts. As a general rule, drainage can be properly applied, 

 and the land freed of both black alkali and white alkali at less expense 

 than by the application of gypsum. Gypsum costs $4 to $10 per ton 

 in the regions where it is needed in black alkali reclamation, and when 

 it becomes necessary to apply sufficient to neutralize 0.1 per cent of 

 sodium carbonate in two or three acre-feet of soil per acre, the cost 

 is seen to be prohibitive. 



Tillage, and Soil Management 



Tillage is the preparing and stirring of the soil with the object to 

 make it more congenial to the growth of plants. On the wise manage- 

 ment of the soil depends the perpetuation of the human race. 



Objects of tillage (King). 



Stated in the broadest and briefest way, the purpose of tillage is 

 to develop and maintain beneath the surface of the field a commodious 

 and thoroughly sanitary home and feeding ground for the roots of 

 crops and for the soil organisms that help to transform the organic 

 matter and the less soluble forms of the mineral plant-food materials 

 of the soil into more soluble and suitable conditions adapted to the 

 immediate needs of plants. But to make the habitable part of the soil 



