Care of the Growing Crop 169 



greatly increase the crop. Hot and dry weather, at or 

 following the time of tillage, may nearly ruin the crop, 

 weakened by root injury. 



Tillage so loosens the upper inches of the soil that the 

 roots cannot develop there until after tillage stops. The 

 plant-food contained therein may be of great value to the 

 growing crop. Exhaustive experiments show that with 

 corn practically the same amount of water is found in the 

 soil late in the season whether tilled or not. The plant 

 roots are able to use the water before it can escape from the 

 surface.^ If weeds have been killed, there is little need of 

 stirring the soil late in the season. The frequent grinding 

 of the upper soil layer by early tillage has changed much 

 of its contained plant-food into a condition in which it is 

 available to the plants. If the previous care has been such 

 that the crop has passed the critical period in good condi- 

 tion, the roots soon fill the surface soil and use the plant- 

 food supply for the production of tubers. A few weeds 

 which may have escaped the tillage tools should be pulled 

 by hand in July and August before they go to seed. 



Spraying is commonly thought of only in its relation to 

 insects and diseases. Thorough spraying with bordeaux 

 has been found to give an increase in yield in the absence 

 of disease and insects. This action is noted most in hot 

 and dry seasons. It should always be considered among 

 the methods to insure good yields in sections where heat 

 and drought are likely to limit the yield. 



I 111. Bui. 181. Bui. 257, Bur. PI. Ind., U. S. Dept. Agr. 



