16 AGRICULTURE 



ever, be plowed to full depth the first season, but should be 

 gradually increased from year to year, as too large a mass 

 of subsoil may be turned up at one time. 



Deep plowing brings to the surface comparatively new 

 and unused soil, admits air and moisture to a greater 

 depth, and allows the roots to penetrate farther into the 

 soil. The turning under of organic matter also provides 

 a supply of humus and makes the lower strata of the soil 

 more porous. 



Why corn needs to be cultivated. Corn is to be cul- 

 tivated after planting for three main purposes: (1) To 

 kill the weeds, (2) to admit air to the roots, and (3) to 

 form dust mulch and preserve the moisture of the soil. 



From the time germination begins the growth of the 

 plant must be unchecked if a full crop is to be secured. 

 When corn has become yellow and spindling from being 

 choked by weeds, or from the baking of uncultivated soil 

 around it, it is permanently injured and will never fully 

 recover. Only the rich green color and sturdy stock of the 

 rapidly growing plant give promise of a full yield. 



When to begin cultivation. Cultivation should begin 

 early. Under average conditions, disking and harrowing 

 before planting and two harrowings after planting should 

 be given before the corn comes up. This will keep the soil 

 from baking, and keep the weeds down until the plants are 

 large enough to cultivate. The time to kill weeds is just as 

 they are starting. Let them once get well rooted, and they 

 are hard to manage. 



The shovel or disk cultivator should be started as soon 

 as the corn is well up, so that the rows can be easily fol- 

 lowed. Even if the weeds do not seem to be starting, they 

 are surely taking root. Cultivation will also break up 

 the crusted soil, and admit air to the growing roots. And 

 this must be done or their growth will be checked. 



