270 SOILS AND FERTILIZERS 



cial sources of phosphate fertilizers ? 209. Give the four cal- 

 cium phosphates and their relative fertilizer values. 210. Define 

 reverted phosphoric acid. 211. Define available phosphoric acid. 

 212. In what forms do phosphate deposits occur? 213. State the 

 general composition of phosphate rock. 214. Explain the process 

 by which acid phosphates are made. Give reactions. 215. How 

 is the commercial value of phosphoric acid determined? 216. 

 What is basic phosphate slag and what is its value as a fertilizer ? 

 217. What is guano? 218. How do raw bone and steamed bone 

 compare as to field value ? As to composition ? 219. What is dis- 

 solved bone? 220. How is bone-black obtained, and what is its 

 value as a fertilizer? 221. How are phosphate fertilizers applied to 

 soils? In what amounts? 222. How may the phosphoric acid of 

 the soil be kept in available condition ? 223. What is the function 

 in plant nutrition of potassium? 224. To what extent is potash 

 removed in farm crops ? 225. To what extent is potash present in 

 soils? 226. What are 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 alkalimetry of an ash? 234. Of what value, 

 as fertilizer, are hard- and soft-coal ashes ? 235. What is the fer- 

 tilizer value of the ashes from tobacco stems ? 236. Cottonseed 

 hulls? 237. Peat-bog ashes? 238. Saw-mill ashes? 239. Lime- 

 kiln ashes? 240. How is the commercial value of potash deter- 

 mined? 241. How are potash fertilizers used? 242. Why is it 

 sometimes necessary to use a lime fertilizer in connection with a 

 potash fertilizer ? 243. What can be said regarding the importance 

 of lime as a plant food ? 244. To what extent is lime removed in 

 crops? 245. To what extent do soils contain lime ? 246. What are 

 the lime fertilizers ? 247. Explain the physical action of lime fer- 

 tilizers. 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? Ex- 

 plain its action. 258. Are sea-weeds of any value as fertilizer? 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. Ex- 

 plain how a commercial fertilizer is made. 263. Why are the 

 analysis and inspection of fertilizers necessary? 264. What are the 



