No. 4.] CHEMICAL AND FARM MANURES. 163 



Iron, though usually ignored as a necessary application 

 for soils, is nevertheless as essential to plant growth as any 

 other ingredient. Fortunately, soils are practically always 

 suflSciently supplied with it. It has been applied, however, 

 in many cases as proto-sulfate of iron (green vitriol) with 

 most marked advantage. However, its usefulness in such 

 cases has been usually by virtue of its liberating potash and 

 possibly other plant food, and sometimes owing to its prov- 

 ing a remedy for certain diseases affecting the roots of 

 plants. 



Sulfur is also an essential element in the growth of plants, 

 though usually soils receive enough of it in the various ma- 

 nures ; many of the German potash salts, as well as super- 

 phosphates, containing large quantities of it in the form of 

 sulfate. 



After what has been said in relation to the special action 

 of different forms of plant food and the influence of the 

 character of the soil upon their assimilability and relative 

 adaptabilities, it must be evident that no general rules for 

 manuring, applicable to all crops, can be laid down for a given 

 soil, nor can specific rules be laid down for a given plant 

 applicable upon soils of all classes. It must be equally 

 manifest that the purchase and use of complete commercial 

 fertilizers without a knowledge of their chlorine content and 

 of the nature of the nitrogenous materials which they con- 

 tain can be classed as neither scientific nor practical ; and yet 

 this is what farmers are forced to do who employ such goods, 

 so long as the analytical data are not sufiicient to tell them 

 what they are actually buying. That the statements of 

 certain manufacturers are and will continue to be misleading 

 there can be no question, unless the consumers ask for what 

 protection they should have. As previously explained, chem- 

 istry has not as ^et been able to tell with satisfactory exact- 

 ness the relative values of the organic nitrogen, though most 

 hopeful progress has already been made. "While waiting for 

 the further perfection of methods to be used in the protection 

 of the interests of the farmer, there should be no neglect of 

 the opportunity to ascertain for him everything that can be 

 determined in relation to the character of the commercial 

 manures. With trusts and combinations to control the price 



