119 



surface, because they are li$it and not packed down by gravity. 



a average dry soil requires 4 ( *-6 w of r^in to saturate the first 



foot of surface soil or from 20-32$ per cubic foot. One cubic foot of 



ordinnry ^n,rden soil loara has about 1 sere or surface exposed by the 

 partic : en. 



Amount of surface is important because: 



iSttS 



TJ More surface more capillary wstor. 



2} Cher?ic*>.l effect on ourfrcc ir-i re"i--r with greater surface 

 of particles . 



. r-holdin[f capacity is of txto kinds: 

 1} ..laum: when saturated. 



2f I'inimum: contains only capillary water; this is the usual 

 -^cily i unlens o th 3 r-vi s ? c^ 



nsil.y of -r rrr;n,;xi?';ent of soil particles: 



Increases minimum -winter holding capacity, therefore cultiva- 

 tion decreases va trrho3 ding capacity. 



reel? of forest cover: "Plocculstion in noil increased "by: 

 ixture of organic life, 



2) 'Action of root* 



Ch.'lc'i ) ons u *> aud- 



3) Cover favor* orgrnic life, a. nacteria. 

 4} Cover favors* underground anixrale, 



'"vaoor^tion is affected "by 4 f^ctorr: 



1} Climate: tempcriture, humidity, wind. 



il: neture: text u r e, , d e p th t c^o^l o^r , a a 1 1 s v/ith affinity for 

 wat> . 



3) Cover: vegetation, humus, etc. 



4) Topof^phy: nlop*, erpopure. 



Relation of Evaporation to Relative Humidity ana lemperntuc. 



Effect of Texture or '?vq..por-".tlcri 



6 days difference. 

 The figure-;? in the table are the evaporation per 1000 

 surf.->C3 exuoiKi in ra^s. 



