EFFECT OF WEEDS ON CROPS 
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proposition calls for an increased development with higher water 
loss by the crop itself, and an elimination of water loss through 
the weed channel. 
SUMMARY 
The results submitted in this paper from greenhouse and field 
experiments show that : 
1. Weeds give ofif a large amount of water. 
2. A mixed culture, that is, one having both cereals and weeds 
growing under the same conditions on an equal surface area, will 
give off more water than a pure culture containing only cereals. 
3. A mixed culture reaches its maximum transpiration period 
at a later date than a pure culture. As there is no material 
difference in the ripening period, the time interval for the forma- 
tion of the grain is shortened. 
4. A cereal like corn responds readily to cultivation. 
Department oe Botany 
Iowa State College 
