NITROGEN, NITRIFICATION, NITROGENOUS MANURES 151 



fertilizer value of the dung is nearly equivalent to the 

 original value of the meal. 



167. Fish Scrap. The flesh of fish is very rich in 

 nitrogen. 49 The offal parts, as heads, fins, tails, and intes- 

 tines, are dried and prepared as a fertilizer. Some species 

 of fish which are not edible are caught in large numbers 

 to be used for this purpose. In seacoast regions, fish fer- 

 tilizer is one of the cheapest and best of the nitrogenous 

 manures. It is richer in nitrogen than tankage or flesh 

 meal, and in many cases equal to dried blood. It read- 

 ily undergoes nitrification and is a quick-acting fertilizer. 



168. Seed Residues. Many seeds, as cottonseed and 

 flaxseed, are exceedingly rich in nitrogen. When the oil 

 has been removed, the flaxseed and cottonseed cake are 

 proportionally richer in nitrogen than the original seed. 

 This cake is usually sold for cattle food, but occasionally 

 is used as fertilizer. It contains from 6 to 7 per cent of 

 nitrogen, and compares fairly well in nitrogen content 

 with animal bodies. Cottonseed cake and meal are not 

 so quick acting as dried blood, but when used in south- 

 ern latitudes a little time before seeding, the nitrogen 

 becomes available for crop purposes. Oil meals, as 

 cottonseed and linseed, containing a high per cent of 

 oil, are much slower in decomposing than those which 

 contain but little oil. It is better economy to feed the 

 cake to stock and use the manure than to apply the cake 

 directly to the land. Occasionally, however, cottonseed 



