324 SOILS AND MANUEES 



Superphosphate also, it is ^said, has a similar effect but 

 not so marked as that of kainite. 



Absorptives. The well-known power of peat to absorb 

 ammonia gas has indicated this substance as likely to 

 prove useful as a means of preventing loss. It has been 

 tried in the ordinary condition and also impregnated with 

 sulphuric acid but without much success. Perhaps a 

 quantity of ordinary loamy or peaty soil might be used 

 with advantage. It costs nothing, does not interfere with 

 the fermentation, and at the worst could do no harm. 

 It would probably prove as efficient as those ammonia 

 fixers which depend upon chemical action. 



COMPOSITION. 



The composition of farmyard manure, it will thus be 

 seen, depends upon a number of variable factors, and 

 the differences in quality are sometimes very great. 

 Practical farmers have always recognised the difference 

 between horse and cow manure, fresh and rotten manure, 

 and they have long been familiar with the improve- 

 ment produced by feeding the animals on cake and other 

 rich food. They do not, however, as a rule, attach so 

 much importance to the conditions under which the 

 manure is made. Under ordinary circumstances, it is 

 perhaps surprising that the variation in composition is 

 not greater than is commonly found. Nevertheless, in 

 the case of mixed manure made with straw litter in the 

 ordinary way, one sample may contain twice as much 

 fertilising matter as another. The proportion of water 

 depends upon accidental circumstances and is very vari- 

 able; as it affects the proportions of all the other ingre- 

 dients, these should be given as percentages of the dry 

 matter, which is the only proper basis for comparison. 

 Unless this is properly understood analyses of farmyard 



