14 

 at work under good conditions of tillage in keeping up the 

 supply. Through the action of certain nitrogen-fixing 

 organisms which live in conjunction- "symbiotically''- with 

 the legumiiaous crops such as clover and vetch, nitrogen is 

 added tothe soil in available form in large amounts. The 

 decay of all organic material is another great scourse of 

 available nitrogen. In this connection the trees supply 

 themselves in some measure with organis nitrogen through 

 the decay of tl.e leaves which fall from them each year. 

 There may be occassions v;hen these sources do not supply 

 sufficient nitrogen in which case any of the following 

 manures may be used; 



Dried blood.- This is obtained by drying the blood and 

 debris from slaughter-houses and as usually sold contains 

 from 9 to 13% available nitrogen. 



Tankage,- This is composed of refuse matter such as 

 bones, trimming of hides, hair, horns, hoofs, and some blood. 

 These are usually dried, ground, and mixed ith a little 

 slaked lime to prevent rapid fermentation. It usually contains 

 from 5 to 7% of nitrogen and because of its slower rate of 

 decay it is not quite so rapidly available as dried blood. 



Flesh meal.- This is the flesh refuse from slaughter 

 houses which is sometimes kept free from the tankage, driecj, 

 ground and sold as flesh meal. It contains from 4 to 8% ni- 

 trogen. 



Pish scrap.- Fish flesh is very rich in nitrogen. The 

 offal parts, as heads, fins, tails, and intestines are dried 

 and prepared as a fertilizer. It readily undergoes fermentation 

 and is therefore a quick-acting fertilizer. 



