SOURCES OF PLANT-FOOD 



Sulphate of Ammonia. - - This is a by-product 

 in the manufacture of coke and also of illuminating 

 gas. Hunt estimates that the amount of nitrogen 

 lost annually in Pennsylvania's coke industry 

 would be sufficient, if recovered by proper type of 

 ovens, to furnish every acre of land under cultiva- 

 tion in the state with four fifths of all the nitrogen 

 needed to keep it in a maximum state of fertility. 



Sulphate of ammonia contains about 20 per 

 cent of nitrogen, which is in a quite available 

 form. It has a tendency to exhaust the lime in 

 the soil, producing an acid condition. Some plats 

 in the fertilizer experiment at the Pennsylvania 

 station have received their nitrogen in the form of 

 sulphate of ammonia for 30 years, and are now 

 in such acid condition that no crops thrive upon 

 them. The corrective, of course, is lime, and if 

 ammonium sulphate were somewhat lower in 

 price, its use would be profitable, justifying cost 

 of correction of acidity if it should occur. It is 

 used by manufacturers of commercial fertilizers, 

 and is well adapted to mixtures on account of its 

 physical condition. 



Dried Blood. There is no more satisfactory 

 source of organic nitrogen than dried blood of 

 high grade. The best blood, red in color, contains 



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