300 SOILS AND MANURES 



by the 'addition of alum and lime. About 10,000,000 

 gallons of sewage are treated daily, and about 4J tons of 

 sludge manure is produced. The latter contains about 

 2 per cent, of nitrogen and 3 J per cent, of tricalcic 

 phosphate. Both constituents appear to be readily avail- 

 able, and the manure fetches a fairly high price. In 

 some cases a mixture of alum, blood and clay is used as 

 a precipitant. The nitrogenous matter of the blood is 

 added to the sludge, and a manure of different composi- 

 tion is produced. 



Liquid Manure. Liquid manure consists of the urine 

 of animals, collected in stables and cowhouses, and the 

 drainings from the yard manure heaps. It is valuable 

 chiefly for the nitrogen and potash it contains, the pro- 

 portion of phosphates being very small. The composition 

 of urine is very variable. It depends, to a large extent, 

 upon the quantity of water and the kind and quantity 

 of food consumed by the animal. Under normal condi- 

 tions the urine of horses and cattle contains from 87 to 

 97 per cent, of water, from 1 to 1.5 per cent, of nitrogen, 

 and a similar amount of potash. Perhaps the best way 

 to utilise it is to pump it over the manure heap. If the 

 latter is dry enough to absorb it, the liquid promotes fer- 

 mentation, enriches the manure, and has a generally good 

 effect. If the heap be too moist to absorb any more, the 

 liquid may be made into a kind of compost by mixing it 

 with a quantity of humus soil or even ordinary dry soil. 

 If it is proposed to utilise the liquid manure in this way 

 or to keep it for any length of time, a small quantity 

 of sulphuric acid should be added to prevent loss of 

 nitrogen by evaporation of ammonia. Liquid manure 

 may also be applied to the land direct by means of a 

 sprinkler, but should be diluted with two or three times 

 its volume of water. In the undiluted state it is apt to 

 produce a burning effect. 



