CAMPBELL'S SOIL CULTURE MANUAL 97 



upward movement of moisture which is brought from the 

 root zone or stratum by capillary attraction to the surface 

 and evaporated. 



The warm sun has set the vigorous plant to work 

 pumping water by means of its many little rootlets up 

 through the stalk and out the leaf. With these two forces 

 at work your moisture is soon depleted below the normal, 

 and chemical action becomes slower. 



Another dangerous factor is also at work, the moisture 

 that is rising to the surface is carrying with it the mag- 

 nesia, alkalies and salts so prevalent in our prairie soils, 

 in a soluble or dissolved condition, and as they reach the 

 surface the moisture is lost in vapor. 



These mineral substances are deposited between the 

 surface soil grains, and if this process go^s on long enough 

 the surface becomes solid and the air nearly or quite ex- 

 cluded. The moment this condition becomes general 

 practically all growth ceases from a lack of air though 

 there may be plenty of moisture. Therefore the vital 

 importance of harrowing this surface as explained in other 

 chapters. 



The Cut No 9 on page 76 illustrates quite clearly the 

 ideal physical condition as compared with the more com- 

 mon haphazard manner. Study the two views carefully, 

 and think of what you have seen in the field and how 

 different were the results. 



It is our opinion that upon this ideal physical condi- 

 tion of the soil grains as shown in the above cut, as well 

 as others shown in previous chapters, depends very largely 

 the magnitude and quality of the crop. This conclusion 

 is not based on theory, but upon results obtained in many 

 tests following these lines. 



