25 



Nitrogen recovered for 100 applied in Manure. 



L — Wagner's Results. 



Manures Manures 



applied alone with fcLorve Dung 

 Nitrate of Sodium 77 :>2 

 Sulphate of Ammonium 69 50 

 Cattle Urine 69 *0 

 Pasture Grass 43 20 



2.— Maekcker's Results. 



Manures Manures with 



applied alone Farmyard Manure 



Nitrate of Sodium 55 35 



Sulphate of Ammonium 37 Si 



Cow Urine 29 22 



Wagner employed in the above experiments, 2 grams of nitrogen 



as nitrogenous manure, with, or without, 2 grams of nitrogen as horse 



dung. Maercker used *75 gram of nitrogen as nitrogenous manure, 

 with or without 1*5 gram of nitrogen as farmyard manure. 



The German investigators are doubtless right in attributing the de- 

 crease in the return from nitrate of sodium, when mixed with dung or 

 farmyard manure, to the destruction of the nitrate occasioned by the 

 latter manures, but Wagner will not admit that the decrease in the re- 

 turn from ammonia, urine, or grass is due to the diminished rate of nitri- 

 fication of these manures brought about by their mixture with much 

 organic matter. His argument is peculiar. He says : we cannot explain 

 the depressing action of the dung when applied with urine or grass as 

 due to any hindrance in the conversion of their nitrogen into ammonia, 

 because the yield of ammonium salts also suffers under these circum- 

 stances : and we cannot explain the depression in the case of ammonium 

 salts as due to want of nitrification, as the nitrates applied equally show 

 the injurious effects of the dung. Might we not add, with as much jus- 

 tice : we cannot explain the action of dung on nitrates as due to denitri- 

 fication, as the dung occasions an equal depression where no nitrates 

 have been applied ? This mode of argument is valueless : all it can pos- 

 sibly prove is that a single explanation will not suffice for all the results 

 before us. 



It is generally assumed by the German investigators that denitrifi- 

 cation is a sufficient explanation of all the results obtained ; it is appar- 

 ently supposed that the ammonia, urine, and grass have nitrified in the 

 soil just as usual, and that the nitrate produced has heen destroyed by 

 the dung. But it is proved in the course of the German investigations 

 that the reducing action of the dung is greatest immediately after its 

 application to the soil, and gradually diminishes with the lapse of time. 

 We have, then, the conditions producing denitrification set up most 

 actively at the first, and we may well ask — How can nitrification take 

 place under these circumstances ? That nitrification will eventually set 



