REVIEW QUESTIONS 335 



the sources of the soil's potash ? 227. What are the various sources 

 of the potash used for fertilizers ? 228. What are the Stassfurt salts, 

 and how are they supposed to have been formed ? 229. What is 

 kainit ? 230. How much potash is there in hard wood ashes ? 231. 

 In what ways do ashes act on soils ? 232. How do unleached ashes 

 differ from leached ashes ? 233. What is meant by the alkalinity 

 of an ash ? 234. Of what value, as fertilizer, are hard- and soft- 

 coal ashes ? 235. What is the fertilizer value of the ashes from 

 tobacco stems ? 236. Cottonseed hulls ? 237. Peat-bog ashes ? 

 238. Sawmill ashes ? 239. Lime-kiln ashes ? 240. How is the 

 commercial value of potash determined ? 241 . How are potash 

 fertilizers used ? 242. Why is it sometimes necessary to use a lime 

 fertilizer in connection with a potash fertilizer ? 



CHAPTER IX 



243. What can be said regarding the importance of calcium as a 

 plant food ? 244. What is lime, and to what extent is it removed 

 in crops ? 245. To what extent do soils contain lirne ? 246. What 

 are the lime fertilizers ? 247. Explain the physical action of lime 

 fertilizers. 248. Explain the action of lime on heavy clays. 249. 

 On sandy soils. 250. In what ways, chemically, do lime fertilizers 

 act? 251. How may lime aid in liberating potash ? 252. What is 

 marl ? 253. How are lime fertilizers applied ? 254. What is the 

 result when land plaster is used in excess ? 255. Explain the action 

 of salt on soils. 256. When would it be desirable to use salt as a 

 fertilizer ? 257. Is soot of any value as a fertilizer ? Explain its 

 action. 258. Are seaweeds of any value as fertilizer ? What is the 

 fertilizer value of street sweepings ? Of garbage ? 



CHAPTER X 



259. What is a commercial fertilizer? An amendment? 260. 

 To what does the commercial fertilizer industry owe its origin? 



261. Why are commercial fertilizers so variable in composition? 



262. Explain how a commercial fertilizer is made. 263. Why are 



