53 



Effeet of Veefla on LiFJa%. wanath: and Proteetion fr om 

 Alt Currents* 



In a German experiment (E. S. R. 16, 883 ; Fuhling's 

 Landv. Ztg. 53) weeds graving in potato^js, beans, and maize 

 lowered th© t*»mpdratur© 2° to 4° C. through "shading and 

 transpiration, " 



The results of an experiment at the lUnnssota Btation 

 (Bui. 68, 585), where th© tomperature of th© soil -where no 

 vegetation was -^^ro-^ing vas compared with that wteia.^-6 wheat 

 was groining thou,'^h not strictly comparable with weeds growing 

 in crops, v/ould nevertheless be of some value for this 

 purpose. V'hsre the wheat was growing the t*»nip->-r'fetture was 

 about 5° lower than where the ground was bare. 



Manifestly where w^j^ds 2:rowing m corn exelud© the 

 light from the lower leaves, the efficiency of this part 

 would be lessened. Since soil bact*:>ria require abeen- e of 

 light, ij i"^ possible that nitrification wUl occur el.ee^^r 

 to the surface than where weeds are not growing xn corn, 

 proviuing the raoisture ©ontent remains the fif^rae ? 



Suppose a f!:'W siaall weeds were growing in corn, but 

 having a large shading capaoity for the plant food and water 

 coneumed ; wouxd the surface soil feave a better moisture 

 condition for nitrification ? In ordinary field conditions 

 the scant moifiture for aueh of the growing season hinders 



