NITROGEN GROUP OF FERTILIZERS 23 



and then sold as a fertilizer. Whilst fish guano is of very 

 varied composition, the product of any one factory is often 

 quite constant. The average of a large number of samples 

 obtained from North Shields has been : — nitrogen 80 per 

 cent. ±0-2, phosphoric acid=5-9 per cent. ±0*8, potash=i-i 

 per cent. ±0*3. The nitrogen is so much higher in amount 

 and fertilizing value than the other ingredients that this 

 fertilizer may be looked upon as belonging to the organic 

 nitrogen group. Like all the members of this group, fish 

 guano is much slower in its action than sulphate of ammonia 

 or nitrate of soda. Its decomposition in the soil depends 

 upon living things, from bacteria upwards. Moisture, 

 warmth, and lime in the soil greatly facilitate its action. 

 In addition to its purely chemical value the physical properties 

 must be considered (see p. 68). 



An objection to fish meal, not uncommon to the whole 

 of this group, is that it is sometimes too attractive to birds, 

 or even four-footed beasts. Crows have been known to 

 pull it out of the soil almost as fast as the farmer had put 

 it in, and in India it has sometimes induced the wild pig 

 to root it out and trample the field. For cold situations, 

 or for late application, or for top dressing this manure is 

 inferior to sulphate of ammonia or nitrate of soda. 



Dried Blood. — Dried blood is generally only the clot, 

 and not the entire blood, as the boiling down of big quantities 

 of blood is a difficult problem. Fresh blood, when obtain- 

 able, can of course be used also. Blood decomposes in the 

 soil with great rapidity. Dried blood, as a rule, contains 

 from 9 to 12 per cent, nitrogen. 



Hoofs and Horns. — These are the product of the 

 slaughter-house, and are much used by the manufacturers 

 of artificial manures. They contain from 12 to 16 per cent, 

 of nitrogen. The raw horn swells very slowly in the soil, 

 and acts slowly, but if horn be steamed it swells up quickly 

 in moist soil, and produces a moderately quick- acting fertilizer. 

 This material must, in any case, be very finely ground. 



Wool Waste, Shoddy, Feather Waste, Feather Dust, 

 and Silk Waste, are all waste products of a fibrous and 



