272 SOILS AND FERTILIZERS 



may a rotation make an even distribution of farm labor? 307. How 

 are manures used to the best advantage in a rotation? 308. In what 

 other ways are rotations advantageous? 309. What may be said re- 

 garding long- and short-course rotations? 310. How is the conser- 

 vation of fertilitv best secured? 311. Why does the use made of 

 crops influence fertility? 312. What are the essential points to be 

 observed in the two systems of farming compared in Section 323? 

 313. Is it essential that all elements removed in crops should be re- 

 turned to the soil in exactly the amounts contained in the crops? 

 Why? 314. How does manure influence the inert matter of the 

 soil? 315. What general systems of farming best conserve fertility? 

 316. Under what conditions may farms be gaining in reserve fer- 

 tility? 317. Why in continued grain culture does the loss of nitro- 

 gen from a soil exceed the amount removed in the crop? 



CORRECTIONS 



Page 25, line 19, for "three months," read "two months." 



Page 28, line 18, after soil, add : "absorbed from the air." 



Page 28, line 26, add : "when reduced below 4 per cent." 



Page 64, line 5, for "one-half," read "one-tenth." 



Page 72, line 18, read"94," not "96." 



Page 150, line 2, read "clover hay nitrogen, 35," not "45." 



Page 187, under Flax, transpose "19" and "8." 



