122 Bulletin 174. 



1-1. Must all food materials in the soil he in solution hefore the 

 plant can use them f 

 Yes. 



15. Does the plant ever utilize materials which are insohoble in 

 the soil water f How f 



Yes ; the roots of plants are sliglitly acid and this increases the 

 dissolving power of the moisture in contact with the roots. 



16. How is it thatpjlants can live and grow in a soil which is dust 

 di'y f 



Even the soil which seems to us dust dry really contains very 

 minute amounts of water ; and so long as this is the case osmotic 

 action goes on though, of course, very slowly when the soil is " dust 

 dry." 



17. Can your soil he so loose as to have too much air for the 

 good of the plants f 



Yes.' This is sometimes the case in very light sandy or gravelly 

 soils. 



18. Do you understand that you can smother the root as well as 

 the top) of the plant f How f 



Yes. The roots need air as well as the top. Soil which is con- 

 stantly soaked with water prevents the air from coming in contact 

 with the roots ; smothering results as one of the eflects of too wet 

 land. 



19. At 'iohat season do yoio sihppose that corn roots ahsorh the 

 most moisture f 



AYhen the corn is making its most rapid growth. 



20. At what season do you have the least rainfall f 



During the sununer season when plants are growing most rapidly. 



21. If you knew that you would not have sufficient rainfall in 

 August to maintain your potato crop^ how would you plan to 

 secure the moisture? 



Prevent evaporation as far as possible by means of a surface 

 mulch. This means thorough tillage. 



22. Name one way in which plants are injured hy too strong 

 dressings of potosh or nitrogen. 



If applied in such large quantities that the soil moisture dissolved 

 larger proportions than were contained in the sap — that is, if the 



