BOGENHAtTSEN EXPERIMENTS. 287 



was sown and harrowed in, on one day : immediately 

 after the sowing there was a moderate thunder shower. 

 The field was divided into seventeen lots, each of 

 1900 square feet, which were separated from each other 

 by furrows ; each was separately sown and harrowed. 

 The quantity of guano used was 18-8 Ibs. ( = 23 -3 Ibs. 

 avoir.), and the weight of the salts of ammonia employed 

 was calculated from the amount of nitrogen in the guano, 

 so that, as in the previous experiment, each plot received 

 an exactly equal amount of nitrogen. The results were 

 the following : 



Experiment in Bogenhausen. 



RESULT OP HARVEST, 1858. WINTER-WHEAT. 



Corn. Straw. 



grammes. grammes. 



Manured with guano, yielded ................. 32986 791 60 



19600 41440 



21520 38940 



25040 57860 



27090 65100 - 



sulphate of ammonia (11 '8 Ibs. Bav. 

 phosphate " (11*9 

 carbonate " (10-6 

 nitrate " ( 7'1 



TJnmanured ................... ." .......... '... 18100 32986 



These experiments show in the clearest manner that 

 it is an error to refer the effect of a powerful nitroge- 

 nous manure chiefly to the nitrogen which it contains. 

 ]STo doubt it has a share in the operation of these ma- 

 nures, but their energy is not in proportion to the 

 amount of nitrogen in them. 



If ammonia or salts of ammonia increase the prod- 

 uce of a field, their effect depends upon the nature of 

 the soil. What we mean here by the nature of the soil 

 is understood by every one ; the ammonia can engender 

 in the soil no potash, no phosphoric acid, no silicic acid, 

 no lime ; and if these substances, which are indispensa- 

 ble for the developement of the wheat plant, are not 

 found in the soil, the ammonia cannot produce any 

 effect whatever. If, then, in Schattenmann's experi- 

 ments, and those at Bogenhausen, there were no results 

 from the salts of ammonia, this did not arise from the 

 fact of these salts being in themselves ineffective ; but 

 they were inactive, because the conditions of their ac- 



