SOIL IMPROVEMENT 85 



not readily available in it. Its crops suffer from both wet and dry 

 weather, from wet because water stands on it and drowns the 

 plants, from dry because water does not rise freely in it and because 

 it becomes so hard that roots cannot penetrate it. 



How can its faults be corrected? If it be low, it needs to be 

 drained to remove surplus water. Then it needs to be made more 

 open and porous by applications of lime, green 

 manures, and coarse stable manure. It is espe- 

 cially important for clay soils to be worked 

 when in proper condition, for they are injured 

 by tillage when too wet or too dry. They are 

 improved by being ' put down ' in grass, both 



Clay soil plowed when 



to avoid tillage and to increase their store of too dry ; it is hard and 

 plant food. Clay soils retain manures and fer- cloddy. 

 tilizers better than do sandy ones. 



Improving Loams. A loam, especially a limestone loam,,, is 

 naturally a good farm soil. It can be kept so by proper tillage 

 and by returning to it the humus and plant food removed by 

 cropping. 



Reclaiming Alkali and Swamp Lands. On alkali lands, as 

 you have learned, there are deposits of mineral salts. These salts 

 are brought to the surface by capillary attraction, and the rainfall 

 is not sufficient to drain them off. Such soils need irrigation, 

 drainage, and deep plowing to free them from these salts. 



Swamp soils are generally of good texture and rich in plant food; 

 if relieved of surplus water, they are very productive. 



EXERCISE 



i. In the exercises under Drainage, Irrigation, Tillage, Crop Rotation, 

 Green Manures, Stable Manures, and Commercial Fertilizers, there are 

 suggested experiments which show methods of improving soils. 



