33$ SOILS AND FERTILIZERS 



grain culture does the loss of nitrogen from a soil exceed the 

 amount removed in the crop? Will a crop rotation alone maintain 

 the fertility of the soil ? 



CHAPTER XIII 



318. Why do soils need further treatment than plowing for the 

 preparation of the seed bed? 319. Why should different soils receive 

 different methods of treatment in the preparation of the seed bed ? 

 320. How would you determine the best treatment to give a soil for 

 the preparation of the seed bed? 321. How do different methods of 

 plowing influence the condition of the seed bed? 322. Why does 

 complete inversion of sod frequently form a poor seed bed? 323. 

 How should the plowing be done to form a good seed bed? 324. 

 Why is it economy to pulverize the soil as much as possible when 

 it is plowed? 325. What effect does the moisture content of the 

 soil at the time of plowing have upon the condition of the seed 

 bed? 326. What effect does an excess of moisture have upon the 

 plowing and working of clay soils? 327. In what condition should 

 the seed bed be left as to fineness? 328. What is gained by fining 

 and moderately firming the seed bed? 329. Why is aeration of 

 the soil necessary? 330. Why do different soils require different 

 degrees of aeration? 331. Under what conditions can the seed 

 bed be prepared without plowing? 332. On what kinds of soil is 

 such a practice not advisable? 333. When is it advisable to mix 

 the subsoil with the surface soil? 334. When is it not desirable 

 to mix the surface soil and subsoil? 335. How can the plowing 

 and cultivation of the soil best be carried on to destroy weeds? 

 336. In what way does cultivation influence bacterial action in the 

 soil? 337. What classes of compounds in the soil are subject to 

 bacterial action? 338. How does the action of bacteria affect the 

 supply of available plant food? 339. What is meant by inocu- 

 lation of soils ? 340. In what two ways can this be accomplished? 

 341. What soils are most improved by inoculation? 342. What 

 soils are least in need of inoculation? 343. What other treatment 

 must often be combined with inoculation? 344. Why do different 



