MANCTRES 101 



the other hand, the production of caibpn'diq^idjejln^^^tj nitci- 

 stices of the manure tends to lessen the loss by volatilisation 

 of ammonia. In any case, it is desirable to regulate fermenta- 

 tion so that it goes on regularly, but slowly, and without any 

 excessive rise of temperature. This can be done by a careful 

 admixture of horse and sheep manure which are " hot ' (i.e.^ 

 very prone to rapid fermentation) with cow and pig manura 

 which are " cold " (i.e., ferment slowly), and by keeping the 

 manure moist by occasionally pumping the drainings from thi 

 tank on to the heap. 



The other way in which nitrogen is lost is by the decom- 

 position of the nitrogen compounds and the evolution of the 

 free element. This is the result of the action of micro- 

 organisms in the absence of air. A compact and a thoroughly 

 sodden state of the heap are the conditions favourable to this 

 action. The loss of nitrogen from a manure heap can be 

 greatly lessened by mixing or covering it with soil or peat 

 moss. Another even more effective plan is to add some acid 

 substance — e.g., superphosphate, or even sodium acid sulphate. 

 An obje3tion to these preservatives has been made on the score 

 that they act not merely as absorbents, but as antiseptics, and 

 prevent the decay of the litter. 



Other OPganic Manures.— The following substances are 

 also used as manure : 



1. Guano. — This consists mainly of the dried dung of sea- 

 birds. It is found on the coasts of tropical seas. Two 

 varieties are now used, one rich in both nitrogen and phos- 

 phates, the other poor in nitrogen but very rich in phosphates. 

 Great variation in composition is shown by guano. An average 

 sample of the first class might contain 7 or 8 per cent, of 

 nitrogen and about 11 per cent, of phosphorus pentoxide, 

 vhile for the second variety 0*5 to 2 per cent, of nitrogen and 

 20 to 33 per cent, of phosphorus pentoxide would be fairly 

 representative. Potash is present in many samples of guano, 

 to the extent of about 2 or 3 per cent. 



