46 RESULTS OF EXPERIMENTS AT ROTHAMSTED, 



whether the higher plants do bring free nitrogen into combination at 

 all. Quite recently, however, he has made new experiments, from 

 which he concludes that nitrogen is fixed under the influence of 

 electricity, both in the soil with its microbes, but without higher 

 vegetation, and in soil with higher vegetation. 



Obviously if there are organic compounds within the soil which 

 have the power of bringing free nitrogen into combination under the 

 influence of electricity, the soil may be the source, and yet the agent 

 may be the feeble electric current. But, so far as it is assumed that 

 free nitrogen is brought into combination in the atmosphere itself, the 

 resulting compounds will be found in the air, and in the aqueous 

 depositions from it ; and the limit of the amount of combined nitrogen 

 so available over a given area, in Europe at any rate, is pretty well 

 known. 



M. Dehe"rain sought to determine the actual losses or gains in the 

 field, under the influence of different manures, of different crops, and 

 of different modes of cultivation. Experiments were made with 

 various crops, each of which was grown without manure, and with 

 three different descriptions of manure, applied for a series of years, 

 and then the crop was grown without manure for some years more. 



The nitrogen was determined in the soil, before the commencement 

 of the experiments in 1875; in 1878 after three years of manuring 

 and cropping ; in 1881 after four years' cropping without further 

 manuring ; and in the case of sainfoin followed by mixed grasses, in 

 1885 also. Lastly, the nitrogen in the crops was only estimated. From 

 these data, the losses or gains of nitrogen by the soil, during the 

 different periods, under the influence of the different manures and 

 crops, were calculated. 



With regard to the actual amounts of loss or gain of nitrogen 

 found in M. Deh6rain's experiments, the losses especially are extremely 

 large, indeed they were far in excess of anything that has come within 

 our own knowledge and experience, and they were in amount such as 

 reflection must show cannot possibly occur in actual practice. 



The question arises how are such results to be explained ? I 

 think there can be little doubt that in the method of taking the 

 samples of soil for analysis, an explanation is to be found ; and I have 

 the less hesitation in suggesting this, since we fully admit, that our own 

 early results, obtained under somewhat similar conditions, are quite 

 inapplicable for anything like accurate estimates of nitrogen per acre. 



In fact, it may be concluded that, certainly the estimated losses by 

 the surface-soils, and probably also the estimated gains, are higher than 

 can possibly happen in practice ; and that the results are due to the 

 samples of soil not being taken in such a way, as to ensure strictly 

 comparable estimates at the different periods. At the same time, there 

 can be no doubt that there would be losses beyond those due to the 

 removal of the crops, under the conditions in which losses were found ; 

 that is when the land was under arable culture. Nor can there be any 

 doubt that there would be gains in the surface-soil, when the land was 



