FAEMYAED MANUEE 323 



phate, which has the further advantage that it fortifies 

 the manure in the constituent (phosphoric acid) in which 

 it is most deficient. On the other hand, it deteriorates 

 the manurial value of the superphosphate. The phos- 

 phate is precipitated, and though the compound is readily 

 available to plants, it probably does not .become so finely 

 mixed with the soil, which is the peculiar advantage of 

 superphosphate. Acid substances should not be mixed 

 with -manure that is to be trodden by animals, as they 

 have an injurious effect upon their hoofs. Sulphates, 

 whether neutral or acid, are objectionable on another 

 ground; they are easily reduced to sulphides which, in 

 large quantity, are deleterious to the crops. 



Instead of sulphates, hydrochloric acid and neutral 

 chlorides have been used. Of these, kainite has been, per- 

 haps, the most largely employed. It is open to the objec- 

 tion, however, that farmyard manure does not generally 

 require the addition of potash, and it is not profitable to 

 use it solely for the saving of nitrogen which it effects. 

 Besides, chlorides, like sulphides, have a deleterious 

 effect on vegetation. 



Antiseptics. More recently it has been proposed to 

 treat the manure with antiseptics in order to arrest or 

 retard fermentation. These are generally more expen- 

 sive and not more effective than the simple ammonia 

 fixers previously mentioned. If they were effective their 

 use must be unsparingly condemned because, in that 

 case, the straw would not be converted into humus and 

 the insoluble plant "foods would not be rendered avail- 

 able. Volatile substances which are transient in their 

 effects and only delay fermentation are not so objection- 

 able, but they are of very little practical use. One of 

 the objections to the use of kainite as an ammonia fixer 

 is that when used in sufficient quantity, the antiseptic 

 action of the chlorides prevents the manure from rotting. 



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