54 



Bitrification on the inuaediats aurfaca. 



If a Xiraitvd aa-oimt of Bfaall woeda under the same 

 eondltionB ehouid caus« an iner»»ag© in nitt'4ti,*ja, will 

 there be a suf fieient increases to mors than baiancr; t-he 

 amount of nitrat<9S consumed by them ? There vouid ba 

 probably left; temporary loss of food constituents by 

 aceusulation on t'le eurfac©. 



It would seem, on the ether hand, that thi* lt»s£'^ning 

 of th6 tsmp'i.rfeitvre of the. soil rr.i.Tht be aetrinental, but 

 this sSttEDS to be uncertain. If detrimental in & northern 



» 



latitude, will it nvcessarily b^ true farther south ? 



^ad© by lowering th® tc»rop-%r&turd lessens feT'aporation 

 from the surface of the soil. Corn while lesKsning evapora- 

 tion does not aGcomplieh thie r-sBult '*8 well as when Vv<?eds 

 are growing with it. y^B'fds iike?;i3fc ascist the rem in 

 hindering the mov6imt.nt of the air ov-r th^ eiuTac©. tht»reby 

 lessening ^■vB.rorSitxon from the surface, Kmrr, fri», Rpt, 

 11, 309) found that ^ass ratter was ev«poratf?d froio. «* pan 

 when placa-rl to the inteward of an oak grov=i, hedge, and 

 elOY-ir field, Thie was probably due both to th* lessening 

 of the vsloeity of th® wind, and to th^ atiaosphe^P;^^' Acquir- 

 ing fiome moi«tur«> from the windbreaks. 



