CULTURE OF I\IAIZE 



219 



Quiroga has shown that early plowing as compared with late 

 plowing may not only increase the percentage of moisture in the 

 soil and the yield of maize, but that the nitric nitrogen in the 

 soil may be considerably increased. The available nitrogen in 

 parts per million of dry soil was found to be as follows : ^ 



Month Early plowed Late plowed 



April 

 June 



July . 



August . 

 September 



Season April to September . 4.51 2.83 



On the other hand, early plowing decreases the amount of 

 organic matter which will be incorporated in the soil if the land 

 is in sod or a cover crop. Where the land is badly infested 

 with perennial weeds, such as the bindweed or morning glory, 

 late plowing destroys the growth already started and gives the 

 maize plant a chance at least to start even. When the land is 

 plowed immediately before planting, it may be at once dragged 

 or rolled and then harrowed and planted while the surface is 

 still fresh and moist. When the plowing is done earlier in the 

 spring the surface requires working at once to prevent it from 

 becoming hard, thus generally increasing the amount of labor 

 to get a good seed bed. 



297. Depth of Plowing. — ^While the variation in the depth of 

 plowing seriously influences the cost of raising maize, since the 

 draft of the plow is nearly proportional to the amount of soil 

 turned, yet the investigations on this subject are quite unsatis- 

 factory. In only one instance has a station reported results on 

 depth of plowing for more than one year upon the same land. 

 Undoubtedly the best depth will vary with the soil, the climate, 

 the season, often with the previous crop grown, and the applica- 



I Ohio State University BuL Series 8. Na 2S. 



