23 



The Gehman Rhsultb. 



The German culture experiments were made, as already mentioned, 

 in large cylinders, the cylinders in each series containing the same 

 weight of soil. As the object of the investigation was to ascertain the 

 comparative value of different nitrogenous manures, applied alone or to- 

 gether, the quantity of each manure applied to the soil was such that 

 each pot received the same quantity of nitrogen. Although, however, 

 tlie quantities of nitrogen applied in comparative experiments were the 

 same, the quantities of organic matter applied were very different. When 

 nitrate of sodium and sulphateof ammonium were used, the manure supplied 

 no organic matter to the soil. When urine or dried blood was made use 

 of the supply of organic mattter was very small. With green manures 

 (green lucerne, or young grass) the supply became much more consider- 

 able. With dung and farmyard manure the supply of organic matter 

 became very large. In the experiments with straw the maximum sup- 

 ply of organic matter was reached. 



The details given of the experiments are frequently too incomplete 

 to enable us to state with perfect accuracy what was the weight of man- 

 ure employed in every experiment, the mere fact that it contained 

 so many grams of nitrogen being sometimes the only information afford- 

 ed. It. is possible, however, to state approximately what quantities of 

 manure would be required to supply the unit of nitrogen adopted, and 

 what quantities of organic matter would be contained in each dressing 

 of manure. The data required for these calculations have been obtained 

 from Wolff's tables when not supplied by the experimenters themselves. 



Weights of Manure Supplying two Grams of Nitrogen. 



Fresh Weight. Dry Organic Matter. 



Grams. Grams. 



Cattle Urine - — 6-10 



Dried Blood - 14 12 



Pasture Grass - 157 31 



Young Lucerne - 200 ? M ? 



Sheep Manure - 200 66 



Oow Dung - 524 85 



Horse Dung - 513 103 



Farmyard Manure - 300-600 65-130 



Rye Straw - 500 409 



If the results which followed the application of these manures are 

 borne in mind, it will be seen that the return in the crop for the same 

 -quantity of nitrogen applied became, as a rule, rapidly less as the amount 

 of organic matter associated with the nitrogen increased. Thus, in one 

 series of Wagner's experiments, the nitrogen recovered in a crop of oats 

 for 100 applied as manure was in the case of : 



Nitrate of Sodium 77 Farm Manure (good) 8 



Sulphate of Ammonium 69 u " (poor) 6 



Cattle Urine 69 



Dried Blood 50 Cow Dung t 



Young Grass 43 Horse Dung 



