122 Bulletin 17.t. 



14. Must all food raate/'ials in the soil he in solution before the 

 jplant can use them f 



Yes. 



15. Does the plant ever utilize materials tvhich are hisoluhle in 

 the soil loater f How f 



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

 dissolving power of the moisture in contact with the roots. 



16. Hoto is it thatjylconts can liiie and grow in a soil which is dust 

 dry? 



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. Tliis 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 effects of too wet 

 land. 



19. At xohat season do you suppose that corn roots absorb the 

 most 'moisture f 



When the corn is making its most rapid growth. 



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



During the summer season when plants are growing most rapidly. 



21. If you hnew that you would 7iot have sufficient rainfall in 

 August to maintain your ptotato crop, liom 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 loay iri which plants are injured by 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 



