Farmyard Manure. 



21 



gypsum, costing is., for each ton of farmyard manure made. 

 Besides the question of cost, another great drawback to the 

 use of gypsum lies in the fact that the calcium sulphate is 

 itself liable to bacterial change ; during the storage of the 

 dung it is reduced by anaerobic bacteria to the state of calcium 

 sulphide, which afterwards acts injuriously on plant life when 

 the farmyard manure is applied to the soil. 



Another suggestion has been to use kainit, because it is 

 composed of salts of magnesium and potassium which will to 

 a certain extent be transformed into carbonates and fix the 

 ammonia as chloride or sulphate. Here again the quantity 

 required is very large, though the soluble nature of the kainit 

 enables it to be utilised more thoroughly. But of this class 

 of substances the most effective is superphosphate ; the acid 

 calcium phosphate it contains reacts with the ammonium 

 carbonate to form a double ammonium calcium salt, insoluble 

 indeed, but very readily available for the plant. The same 

 objections, however, apply to superphosphate as to gypsum ; 

 uneconomical quantities are required if the fixation of the 

 ammonia is to be complete, the superphosphate itself contains 

 gypsum which becomes reduced to the injurious calcium sul- 

 phide, and again the acid superphosphate is found to be harmful 

 to the feet of the animals treading down the litter among which 

 it is strewn. 



Sulphuric acid itself has been tried, as also peat moss im- 

 pregnated with small quantities of the same acid, but neither 

 have proved successful for the reasons indicated above. 



As to antiseptics proper, soluble fluorides and even carbon 

 bisulphide have been tried, but the saving effected in the nitro- 

 gen is never sufficient to pay for the cost of the material and 

 the trouble of applying it. Schneidewind in the course of his 

 experiments at Leuchstadt found that the only practical means 

 of reducing the losses of nitrogen was to place a layer of old 

 well rotted farmyard manure as a basis for the new manure 

 heap ; this had a distinctly beneficial effect and always resulted 

 in smaller losses of nitrogen, possibly because of the constant 

 evolution of carbonic acid from the layer of old manure. 



