SURROUNDINGS OF THE HOME 249 



and root-hairs are all the while in the closest contact with the 

 soil particles. They should not be subjected to any drying 

 effect from large air spaces, for osmotic action through and 

 into the root-hairs is harmfully affected and may be wholly 

 prevented by the drying of their thin porous walls. The 

 finer the particles provided they remain apart from one 

 another, the more surface there is presented for an adhering 

 film of water, and the larger the available water content of 

 the soil for the plant 1 . 



The working of the soil by use of farm and garden imple- 

 ments constitutes tillage. Its chief purposes are to improve 

 the soil structure, to conserve the water content in the soil, 

 and to destroy growths of weeds. The amount of water that 

 a deeply worked fine soil bed will hold is astonishing. For 

 clay soils when saturated it is said to be twenty pounds or 

 more of water per cubic foot. 



Wherever water is in contact with a solid that it wets 

 (clings to), the adhesive force lifts the water more and more 

 until its weight (gravity) counter-balances this adhesion. 

 This is just as true in soils as it is in glass tubes of small size 

 where, in the study of Physics, this phenomenon of capillarity 

 is most commonly noted. It is very commonly a matter of 

 concern for the farmer to conserve the supply of water held 

 in the soil so that plants shall not suffer from lack of sufficient 

 moisture. This is especially true during the growing season 

 with crops that permit tillage. Repeated stirrings of the 

 surface soil interferes with and in a* measure prevents the 

 escape by evaporation of water that has risen from below by 

 capillary action. This water thus becomes available for 



1 A quantity of soil when solidified into a cube having a volume of one cubic 

 inch would have six square inches of surface. If we conceive this same 

 amount of soil as particles in the form of cubes o.ooi inch on a side there would 

 be 1,000,000,000 soil particles. The combined surface of all these separate 

 particles would be 6000 square inches. If the soil particles were one-tenth 

 of an inch in size there would be but sixty square inches of surface. 



