08 THE I'KLNCIPLKS OF A(iRl( TLTrRIv 



Of what is phosphoric acid composed ? In what forms is it to ho 

 found V Of what special use is it to pUints ? Wliy is new land 

 generally well supplied with potash? 



What do artificial fertilizers usually contain? From what sources is 

 nitroo'en obtained for these fertilizers ? Name the diilerent sources 

 of phosjjhoric acid. Flow is potash obtained? 



A\'hat is guano ? What other substances are sometimes useful as fer- 

 tilizers besides those mentioned? In what form is lime found? 

 How is quickUme produced? What is air-slaked lime? In what 

 three ways does lime benefit soil ? 



What is marl? Give the history of its formation. Of what use is it 

 as a fertilizer? 



What is gypsinn? How docs it bcm-fit soil? Is salt a fertilizer, 

 and how ? 



What points should be understood in order to make a proper use 

 of fertilizers ? How may farmers learn what fertilizers contain? 

 How can they learn what the soil re([uircs ? Why does one crop 

 need a different fertilizer from another? Why must soil contain 

 more fertilizing material than the crop uses? Would the surplus 

 be wasted in a clayey soil ? 



"VVhy should chemical fertilizers be i)laced near the surface of tlie 

 soil? Why should they not be allowed to come in contact with 

 seeds and roots? Why should but little be used in the hill? 



AVbv is the manure heap sometimes called the farmer's gold mine? 

 In what three resjjeets does stable manure differ from commercial 

 fertilizers? Why is it a complete fertilizer? 



What part of the elements of plants is retained in digestion? Of 

 what advantage is the bulky nature of manure? How does it ren- 

 der land more moist in a dry time ? "What part of the value of 

 manure may be obtained in the first crop? What are the three 

 sources of loss to which stable manure is subject ? 



What is fermentation ? How is the heat produced ? What substan- 

 ces are lost by fermentation ? "Why is fermentation desirable in a 

 com])ost heap? In what ways may it l)e partly prevented ? 



What is the chief advantage of allowing pigs to run upon the manure 

 heaj) ? What is the value of the litpiid ])arts of manure? What 

 element gives them their chief value ? What ai'C the benefits of 

 using absorl)cnls in tlu^ stable? 



Of what s])eci;d licnefit is gypsum in manure ? How can there be any 



