158 The Rothamsted Grass Experiments. 



eight years previously were still traceable in an increased 

 produce, and in an increased amount of potash in the crop 

 grown. Hermann von Liebig found the amounts of both 

 potash and phosphoric acid considerably greater, particularly 

 in the upper layers of the soil of this wheat field, the greater 

 had been the previous supplies by manure. And Dr. Aug. 

 Voelcker's analysis of drainage waters from different plots of 

 the same field showed very much less loss of potash in that 

 way than of either soda, lime, or magnesia, and also very 

 much less of phosphoric acid than of sulphuric acid or of 

 chlorine. There was, in fact, comparatively little loss by 

 drainage of either potash or phosphoric acid. 



To sum up the last three cases respecting the effects of the 

 different mineral manures when used without artificial 

 nitrogenous supply, the comparison of the results obtained 

 without manure, with superphosphate alone, and with a 

 mixed mineral manure with, and without, potash, brings 

 clearly to view the much more striking influence of an 

 increased supply of potash, than of lime, magnesia, soda, 

 phosphoric acid, or sulphuric acid. It will be observed that 

 this is quite consistent with the facts already set forth in 

 Table XXIX., in regard to the mineral composition of the hay 

 crop. It is true that when there was either a direct supply, 

 or an available residue, of potash, more of the other con- 

 stituents just enumerated was taken up, and even when 

 superphosphate alone was used, considerably more phosphoric 

 acid was taken up, but coincidently there was but little 

 increase of produce, and very little increase in the amount of 

 nitrogen assimilated. 



Effect of Mixtures of Nitrogenous and Mineral Manures. 

 The results hitherto considered have been obtained either by 

 nitrogenous manures alone or by mineral manures alone. It 

 is now necessary to study the results following the applica- 

 tion of mixtures of the two. The order of discussion will be 

 first, the effects of a given amount of nitrogen applied as 

 ammonia- salts, then of double the quantity, then of the 



