150 PRINCIPLES OF PLANT CULTURE 



it contains both potash and nitrogen, but unfortunately 

 its price is too high to permit of its use for this purpose. 

 The muriate, either pure or in crude form (kainit), and 

 sulfate may, on the other hand, be purchased at reasonable 

 prices. The sulfate is considered 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, especially 

 when unleached, as they contain both potash and phos- 

 phoric acid. In leaching, the potash is mostly washed 

 out, but the phosphoric acid is largely retained. Ashes 

 contain no nitrogen. 



265. Nitrogenous fertilizers. — Farm and stable ma- 

 nures should be the first dependence of the cultivator. 

 Aside from these, leguminous 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, however, if sufficient stable manure cannot be ob- 

 tained, more nitrogen may often be profitably used than 

 can be furnished by leguminous crops, hence for these, 

 commercial fertilizers may often be added with advantage. 



266. Signs of lack of food. — Crops suggest their own 

 needs to some extent, 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-de- 

 velopment. 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. 



