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Even S&^^e^e^/ie 



By JONAS VENGRIS, WILLIAM G. COLBY 

 and MACK DRAKE* 



THERE'S MORE THAN MEETS 

 the eye in a cornfield overrun 

 with weeds. We see and understand 

 only the obvious — a field cluttered 

 with undesirable plants. 



Beneath the soil, however, in quiet 

 persistent underground manoeuvers, 

 robber barons of the soil — the lowly 

 weeds — are stealing precious min- 

 erals from the cultural plants, robbing 

 them of healthy growth. 



Competition Great 



It is a common sight to see weeds 

 between cultural plants on grassland 

 as well as on cultivated land. With 

 the weeds sometimes constituting 30 

 to 50 percent of the total yield, the 

 competition for nutrients, light, and 

 moisture is great. 



Since not too much is known of 

 the amount of minerals actually 

 taken by the weeds, a study has been 

 carried on to determine the extent 

 to which weeds compete with cul- 

 tural plants. 



Assistant Research Professor; Head, Agronomy; 

 and Research Professor, Chemistry, respectively. 



Weeds with extensive succulent, 

 leafy growth, such as dandelions, 

 plantain, milkweed, and ferns, con- 

 tain more nitrogen than the culti- 

 vated plants with which they grow. 



According to data accumulated for 

 two years, weeds contained as much 

 or more nitrogen than their asso- 

 ciated forage crop grasses. Since 

 grasses need nitrogen for optimum 

 growth, they must compete strongly 

 against their weed neighbors. 



Some Weeds Thrive on Poor Soil 



Whether grown on grassland or 

 cultivated land, some weeds con- 

 tained more phosphorus than their 

 neighboring cultural plants. This 

 was true for wormseed mustard on 

 grassland and for pigweed on tilled 

 land, which means that certain weeds 

 are winning competitors for phos- 

 phorus. The struggle is less for the 

 weeds but greater for cultivated 

 plants when available soil phosphorus 

 is inadequate. 



Many weeds can utilize soil phos- 

 phorus in "fixed" (not readily avail- 

 able) forms. 



In the clean field, at left, corn has no competition for nutrients and moisture. In the field at right, 

 weeds are competing so strongly that the corn is suppressed, and yield is decreased. JohnH. Vondell 







