NITROGEN 



nitrogen is costly, evaporates easily, leaches quickly, 

 changes by denitrification into volatile compounds, 

 and is altogether elusive. The principal sources are 

 rain, atmosphere, manure and commercial fertiliz- 

 ers. All cover crops prevent leaching, while le- 

 gumes, by accumulations from the atmosphere, leave 

 nitrogen deposited in nodules on their roots. 



Of course, nitrogen is merely an incident — a vital 

 incident — of production. It is one of many ele- 

 ments of plant food, and an abundance of nutri- 

 ment is but one of the indispensable causes of 

 growth. Heat, air, water, tillage, texture and hu- 

 mus are each equally important for a crop. These 

 elements compose fertility ; the several metallic and 

 non-metallic substances we are discussing are the 

 sources of plant food. 



It will neither be attempted to list the commer- 

 cial forms of nitrogen nor to discuss their cost and 

 comparative value. Such information is obtainable 

 from numerous government bulletins, and text- 

 books. Our space is devoted to specific suggestions 

 that will guide the grower in orchard work. Most 

 commercial fertilizers contain less than four per 

 cent of nitrogen, often two per cent. Then in four 

 hundred pounds of chemical fertilizer, the quantity 

 often applied per acre, there are eight to sixteen 

 pounds of nitrogen. As soil has abundance of 

 potash and phosphorus, for orchard uses, without 

 that contained in fertilizers, its value depends large- 



