116. 



j^. Aerntion of soil. 



There are tvo process by v, r hich aeration of the soil may be 

 iirprov : 



1) Bring oxygen into the soil 



2) Take C02 out of tiic soil 



From 8/ to 10^ of the soil volume Must be air, to benefit gras- 

 ses; belo-? this point good grassen wither, and sedges and 3MHfijStk hollow 

 stemmed plants of interior aeration come i . 



Air ;r.ove!r-ent lay be produced by &ny one or more. 1 of the following 

 phenomena : 



1) r-aseous duffmnion 



2) T 'o~ 7 'efn-:' > nt 



3 



.j 



4 



5 



CV l ~ri"~' Of '" '1C 



Change of temper- lure in .a oil or a.traor?pher< 

 "uction pr rind. 



Air motion in the noil depend.?, on the soil; it is better in 

 coars i tixnn in fine clay. ATI experiment showed that: 



flowed 1.6 litre oir to pr.r s thru; 

 ';11 tilled clay *llo--/ed 100-4-00 litres .air to pass thru, 



Air 1-r.ny occur ir ttion in r.cil; ?ir in globules is very re- 

 nistar.t. The amount of $ air in soil depends directly on pore space and 

 water. ~! v "j?l containing f jO-6of' of pore apace, the air space should 

 occupy 1; , ^nn the remainder of th s pore space should, be water. The 

 co: T tb~t ^-ir in the pore spaces verier; it contains more 



th---n thi cat^ide air; it hni3 ?. hi h relative humidity (often satura- 

 i i thf forest); t? . ; orally less oxygen and more nitrogen 

 n in tha outride ir. 



The outeidc cair is by wei^it: ?^A N-, 25^ 0. 



ooil R'Dsorbp ,^asen. ? aaily compressed ases are eailly absorbea; 

 ammonia in n:or easily absorbed than and JU A soil can absorb enor- 

 mous amounts of CO _,, ao much, even, that it can be leached cut. Abeor- 



ion is helped, by*" the presence of mineral compounds in the noil. The 

 three colloids mofit important in aiding absorption in the soil are clay, 

 humus, and iron oxides. 



Oxygon is necessary for bacteria action, deficient air gives 

 reductive fermentation, *nd waptoe nitrogen salts, 



H this point -re will digress from Mr. Roth and insert some dis- 

 cussions of this matter of soil, froin ?.!r. Lei^ J. 



does seven things for the forest cover: 



1) Oivea mechanical support 



2J -Vurninhes v/ator 



3) Furnishes mineral plant food 



4) burnishes organic plant food 

 5J Furnishes free oxygen 



6) Temp err- tare 



7) T/ust be absence of poisons (alkali). 



