Rolling in Relation to Soil Moisture 167 



clear day, and becomes warmer below the surface than 

 ground not rolled. This hastens the rate of evapo- 

 ration from the surface. Then, too, this smooth sur- 

 face allows the wind velocity to be much greater close 

 to the ground, and on this account the loss of water 

 is increased. 



It is often desirable to use the heavy roller in fit- 

 ting ground for seed, and sometimes for the express 

 purpose of bringing an increased amount of moisture 

 to the seed, in order to hasten or to ensure germi- 

 nation when the soil has become dry. But when this 

 has been found desirable, the roller should immedi- 

 ately be followed with a light harrow, in order to 

 restore a thin mulch, which shall check the loss by 

 evaporation from the surface without at the same 

 time preventing the rise of water from below to mois- 

 ten the soil about the seed. 



The press -drill, which has been invented to assist 

 germination, and avoid some of the bad effects of the 

 roller, is a tool employing a sound principle. The 

 seed is well covered to begin with, and then the soil 

 directly above it is firmed by the press -wheel, while 

 the intervening soil is left loose, to act as a mulch 

 and diminish the loss of water, which would be inevi- 

 table with the roller. This tool, however, has a much 

 safer application in the sub -humid regions than it 

 has in the East, where the soil in the spring is natu- 

 rally more moist, and where, for this reason, there is 

 danger of the seed being so closely covered that an 

 insufficient amount of air gets to it to enable 4t to 

 germinate properly. 



