158 Principles of Plant Culture. 



purchased at reasonable prices. The sulfate is consid- 

 ered preferable for tobacco and potatoes as it is thought 

 to produce a better quality of product. The muriate 

 acts more promptly than the sulfate, however. 



264. Wood Ashes are a Valuable Fertilizer, espe- 

 cially when unleaehed, as they contain both potash and 

 phosphoric acid. In leaching, the potash is mostly 

 washed out, but the phosphoric acid is largely retained. 

 Ashes contain no nitrogen. 



265. Farm and Stable Manures should be the first 

 dependence of the cultivator. Aside from these, legu- 

 minous crops (259) are undoubtedly the cheapest source 

 of nitrogen for the farm, and with unleached wood 

 ashes, furnish all the needed fertilizing ingredients for 

 grain crops grown in rotation. For garden crops, how- 

 ever, if sufficient stable manure can not be obtained, 

 more nitrogen may often be profitably used than can 

 be furnished by leguminous crops, hence for these, com- 

 mercial fertilizers may often be added with advantage. 



266. Crops Suggest Their Own Needs to some ex- 

 tent, so long as they are not suffering from drought. 

 As a rule, a lack of nitrogen is indicated by pale-green 

 foliage or small growth of leaf or stalk. Excess of 

 nitrogen is indicated by very large growth of leaf or 

 stalk, with imperfect bud-, flower- and fruit develop- 

 ment. Lack of phosphoric acid is indicated by scanty 

 crops of light or shrunken seeds on plants of normal 

 size. Lack of potash is indicated by small crops of in- 

 ferior fruit, accompanied by satisfactory growth. 



267. Crop Rotation Economizes Plant Food, be- 

 cause some crops use more of a given food constituent 



