REVIEW QUESTIONS 27 I 



usual forms of nitrogen in commercial fertilizers ? 265. Of phos- 

 phoric acid and potash ? 266. How is the value of a commercial fer- 

 tilizer determined ? 267. What is gained by home mixing of fer- 

 tilizers ? 26S. What can be said about the importance of tillage 

 when fertilizers are used? 269. How are commercial fertilizers 

 sometimes injudiciously used? 270. How may field tests be con- 

 ducted to determine a deficiency in available nitrogen, phosphoric 

 acid, or potash? 271. To determine a deficiency of two elements? 

 272. How are the preliminary results verified? 273. Why is it 

 essential that field tests with fertilizers be made ? 274. Under what 

 conditions does it pay to use commercial fertilizers? 275. What is 

 the result when commercial fertilizers are used in excessive 

 amounts? 276. Under ordinary conditions, what special help do 

 the following crops require : Wheat, barley, corn, potatoes, man- 

 gels, turnips, clover, and timothy? 277. In what ways do commer- 

 cial fertilizers and farm manures differ? 278. Does the amount of 

 fertility removed by crops indicate the nature of the fertilizer re- 

 quired? In what ways are plant ash analyses valuable ? 279. Ex- 

 plain the action of plants in rendering their own food soluble. 280. 

 Why do crops differ as to their power of procuring food? 281. 

 Why is wheat less liable to need potash than nitrogen? 282. W 7 hat 

 position should wheat occupy in a rotation? 283. In what ways do 

 wheat and barley differ in feeding habits? 284. W r hat can be said 

 regarding the food requirements of oats? 285. Corn removes from 

 the soil twice as much nitrogen as a wheat crop, yet a wheat crop 

 usually thrives after a corn crop. Why? 286. What help is corn 

 most liable to need in the way of food? 287. What position should 

 flax occupy in a rotation? 288. On what soils does flax thrive best? 

 289. What is the essential point to observe in the manuring of po- 

 tatoes? 290. W T hat kind of manuring do sugar-beets require? 291. 

 Why should the manuring of mangels be different from that of tur- 

 nips? 292. What may be said regarding the food requirements of 

 buckwheat and rape? 293. W T hat kind of manuring do hops and 

 cotton require? 294. What kind of manuring is most suitable for 

 leguminous crops? 295. What is the object of rotating crops? 296. 

 Should the whole farm undergo the same rotation system? 297. 

 What is meant by soil exhaustion? 298. What are the nine impor- 

 tant principles to be observed in a rotation? 299. Explain why it 

 is essential that deep and shallow rooted crops should alternate. 

 300. Why is it necessary that the humus be considered in a rota- 

 tion? 301. What is the object of growing crops of dissimilar feeding 

 habits? 302. How may crop residues be used to the best advantage? 

 303. In what ways may a decline of soil nitrogen be prevented by 

 a good rotation of crops? 304. In what ways do different crops and 

 their cultivation influence the mechanical condition of the soil? 

 305. How may the best use be made of the soil water? 306. How 



