356 
MESSRS. J. B. LAWES AND J. H. GILBERT OR THE RESULTS OF 
preceding, but the earlier accumulations, or what may be called the normal stores of 
the soil and subsoil, would be drawn upon. That such was really the case may be 
concluded from the fact of the reduction of the percentage of nitrogen in the surface 
soil of plot 6, as of plot 7 where mineral manures alone had been applied for 20 years, 
and where the very complex and highly leguminous herbage accumulated, throughout 
the period, an otherwise unaccountably large amount of nitrogen. 
With the differences—in the amount of produce, in the botany, in the character of 
development of the herbage, and in the probable sources of the nitrogen of the crop, 
the change in its chemical composition was also extremely marked. 
Although there was very little less nitrogen taken up than where the ammonia-salts 
were still applied, the percentage of nitrogen in the dry substance of the mixed 
herbage was reduced by more than one-third. In other words, with the increased 
supply of mineral matter there was, for a given amount of nitrogen taken up, a greatly 
increased growth, involving a greatly increased amount of carbon assimilated. 
Of total mineral matter there was, with the increased supply of it, an increased 
instead of a much reduced actual amount of it taken up ; in fact, there was twice 
as much taken up during the seven years as where the application of ammonia-salts 
alone was continued, and the percentage of it in the dry matter of the produce was 
also higher. There was, over the seven years, more of every mineral constituent 
(except soda) taken up on plot 6 with the mineral manure, than on plot 5 with the 
ammonia-salts. Of potass there was nearly four times, of phosphoric acid about two- 
and-a-half times, of sulphuric acid about one-and-a-half time, and of silica (of which 
none was supplied in the manure) more than one-and-a-half time, as much taken up 
as where the ammonia-salts were still used. There was, however, less of every mineral 
constituent (except soda) taken up, than where the mixed mineral manure had been 
applied from the commencement (on plot 7). 
But, notwithstanding the greater actual amount of the mineral constituents taken 
up on plot 6 than on plot 5, there was, with the more healthy character of development 
and better maturation, an actually lower percentage of lime, magnesia, soda, and 
chlorine, in the dry substance of the produce. On the other hand, the percentage of 
potass in the dry substance was considerably more than twice as high, that of phos¬ 
phoric acid one-and-a-half time as high, and that of silica rather higher, under the 
influence of the mineral supply, and with it better characters of growth. Still, the 
percentage of phosphoric acid, lime, and potass, especially of the two latter, was not so 
high as where the mineral manures had been supplied throughout the whole period 
(on plot 7); and where, accordingly, there was a still greater proportion of leguminous 
herbage, and the grasses developed more flower stems. 
In conclusion, it is obvious that it was of potass chiefly, of phosphoric acid also 
notably, but of most of the mineral constituents more or less, that the available supply 
had become so deficient under the continuous application of the ammonia-salts. It 
has already been illustrated how ineffective was a supply of phosphoric acid (super- 
