FAEMYAED MANCJEE 329 



able for the plants. Assuming that the proportion of 

 soluble nitrogen is 0*1 per cent., 10 tons of manure would 

 contain 22 Ibs., a quantity which is equal to 1 cwt. of 

 sulphate of ammonia and is sufficient to account for the 

 immediate and rapid action. The proportion of soluble 

 nitrogenous matter is always small because it is recon- 

 verted by bacterial action into insoluble protein com- 

 pounds which, though not immediately available, prob- 

 ably hecome so very readily. At all events they are 

 probably much more easily converted into a soluble 

 state than the original albuminoids of the dung and 

 litter. It is difficult to say what proportion of the nitrogen 

 may be present in this form. It varies according to the 

 length of time and the conditions under which the manure 

 has been kept. It is perhaps the most valuable part of 

 the manure. Being insoluble it is not liable to loss, yet 

 it is readily available to the plants. It comes into action 

 gradually, thus keeping up a constant supply through- 

 out the period of growth, but is never excessive at any 

 one time. The fertilising ingredients of the unfermented 

 portions of the dung and litter are more slowly available, 

 and it is to these that the manure owes its lasting char- 

 acter. They come into action as the organic matter is 

 slowly oxidised in the soil, and thus a constant but' 

 gradually diminishing supply of available plant foods is 

 maintained, sometimes for many years. The fertilising 

 ingredients in tjiis part of the manure probably exist 

 in many different degrees of availability according to the 

 nature of the materials. The length of time that the 

 manure will last, depends upon the rate at which the 

 plant foods are converted to the available state, and 

 therefore to some extent upon the character of the soil. 

 On open sandy soils the organic matter is more rapidly 

 oxidised and a larger proportion of the fertilising ingre.- 

 dients comes into action each year. The lasting character 



