60 PRACTICAL FARM CHEMISTRY. 



ing water once taken up. This power increases in 

 any soil with the proportion of clay, and still more 

 with that of organic matter in it. Peat, and muck 

 absorb and hold great quantities of moisture, and 

 this sponge-like character, while too prominent to 

 be entirely desirable in such soils themselves, ren- 

 ders them valuable as an addition to sandy soils for 

 the purpose of increasing their absorptive and re- 

 tentive capacities. 



Perhaps the most important quality of clay is its 

 power of absorbing plant foods, such as phosphoric 

 acid, potash, ammonia, lime, etc. , and holding them 

 for the use of plants. Hence soils of a somewhat 

 clayey character can usually be kept in fertile con- 

 dition much more easily than soils that are com- 

 posed mostly of sand. 



