SOIL MANAGEMENT 47 



ment may be better appreciated by summarizing the various 

 effects of drainage. Some of these effects have already been 

 considered; such as modifying the soil temperature, securing 

 a larger feeding area for roots of plants and a better soil 

 ventilation. To these may be added : modifying the structure 

 of heavy soils so as to make them granular and porous; 

 affording conditions favorable for action of bacteria in chang- 

 ing organic matter into available plant food; making it 

 possible for larger amounts of natural plant food of the 

 soil minerals to become soluble. On the whole, drainage may 

 be considered as the first essential of a productive soil. 



It will be seen from this list that drainage is the means of 

 helping to secure a variety of conditions, each of which is 

 important in plant production. 



Tillage. A well-drained soil, important as it is, will not 

 produce satisfactorily unless it is well tilled. The soil must 

 be properly worked and handled in order to secure the best 

 results from good drainage. Each operation of tillage, such 

 as plowing, disking, rolling, and cultivation, has a definite 

 purpose in rendering the soil productive, and each must be 

 done at the right time and in the right way to become the 

 most effective. Plowing when the soil is just right as to 

 moisture content increases the amount of granulation, a 

 condition which has been referred to as good tilth. Disking 

 and harrowing further increase granulation until the seed- 

 bed is made ready to receive the seed. Rolling may prepare 

 the ground in some instances for more effective use of the 

 harrow, or after the seed is in the ground, it may make the 

 soil in the seed-bed compact, thereby bringing moisture 

 from below and thus hastening germination. Finally, culti- 

 vation forms a mulch which prevents the loss of water 

 through evaporation. 



