124. 



humus of tfr- (>.. 



Cultivated l--:nd: soluble -ir l.i (nil:.) form '?$/ in the humus. 



art of the huraua ia-iy exint in ihe soil in corn i nation .ith lime 

 and ol; , beconing soluble only af tc . ction occurs. 



In gr land only 3350 o^ !' ( l : '-racted rith ^.cicL . 



is land v in d.. n'C ar 



'Jot ^1 organi< - . 



acj .8-1. 



need? roper lion ift i o the cjnoant of free huraic 



acid 



K; Biology of th<> :;cil. 



.-oil . i :t in regard to the dt cay and pro- 



Btion , , riti the action of bac'ccria. Study why 



c^rtr-iti r ;o : Lo certain U : i .;on f t know yet &urely; analyses do 



not '-.Iv-'aya e>. rerytl. 



Clr- --cial]. j sture ?xnd temperature) f;nd >"ooa Materials 



I pre the most it. portrait factors in determining UJB life in 

 the tj;e founcirtion of Soil Biology. 



.re are Tour a^cir-a to te considered in Loil I'.iolo . 



t eria 



b. cut cue fun^i 

 . or plants and their effect on soil 



: i . 



a. Bacteria. 



tevia preourtinate mostly in rich tillec, soils, v;hich con- 

 : Lc lifo. 'lliei arc lesu in 'forest soils, but &&& this 



varit-a. Kev.rly all brvcterir- crc sensitive to lijit; i.hey vary in oxygen 



li , . u it in ^oijcrfil; they pro neneitivc to chs.nsfej-? in 



moi. concitione, - i< in very dry conuiLions. All bacteria have 



tor.^u Vhey are sensitive to the action of acids; sour humus 

 'rr lively free from bac-eria. 



cteria excell in h ,<.\^..^\, -..ion ano. u*tili/;-.aiun of all fori.;e of 



ir.on^ ihcicselV'.. i-; ay to wheir /orkan^; torapt.rn.ture, from 

 to very hieUi L sr.pcr ^uic&; some are capable of much higher 

 are th --.-. r* Oti 



-.cteria life is ^enc-rally v.ell uietribu^ea tliru soils except 

 under peculiar conditions, v^here they secrete something which is detri- 

 tal to tlxefiiselves beyond a certain point; oruinjirily tliey are asso- 

 o it3/ other or&ani3ij-B vliich ciay work over these secretions ana thu 



. Thus bacteria may Lc oc. tive in a BGnse. Vliese secre- 



tione are hj.ov?n as toxin ,ti-to;:i. 



.r;e bacteria needing o>:y^cn r.;ay be CGaociauec. -/ith others which 

 rict need oxygen and v/hich r;.r t y j. erh^r.t- e 1 ui prodacu it r.s a by-product 



/tr.n change, due LO uciapera^ure and moisture changes: 

 1} Hinds in soJl 



ortion of kinds 



3) Total nuyther 



4) Activity. 



