318 
MESSRS. J. B. LAWES AND J. H. GILBERT ON THE RESULTS OF 
rather more prominent with the potass. Rumex acetosa was, on both plots, the most 
prominent of the weeds, but yielded somewhat more on plot 7 with, than on plot 8 
without potass. 
The analytical results, which will be fully discussed in Section III., provide the data 
for determining what changes in the taking up of individual mineral constituents have 
taken place coincidently with the great decline in the yield of hay, and the much less 
development of leguminous herbage, on the exclusion of potass from the manure of 
plot 8. Over the 14 years of this exclusion, an average of only about half as much 
potass was annually taken up as during the preceding six years when it was supplied, 
and less than half as much as on plot 7 during the 14 years of the continued applica¬ 
tion. With this reduction in the amount of potass there was considerably more, but 
not correspondingly more, soda taken up. Of lime, magnesia, phosphoric acid, and 
sulphuric acid, although all were liberally supplied, considerably less was taken up on 
plot 8 without than on plot 7 with the potass. Of chlorine also much less was taken 
up on plot 8. Of silica, which was not supplied, even rather more was taken up 
without than with the potass, but with this exception, and that of soda already 
referred to, less of every mineral constituent was taken up on plot 8 without than on 
plot 7 with the potass. Of percentage in the dry substance of the produce, however, 
that of lime, magnesia, phosphoric acid, sulphuric acid, and chlorine, was nearly the 
same without and with the potass; that of soda and of silica was much higher, but 
that of potass was not two-thirds as high, without the potass, though it was still much 
higher than without manure, as also was the percentage of phosphoric acid ; but that 
of the other constituents was, for the most part, much the same as without manure, 
excepting the lime, which was considerably less both without and with the potass. 
A consideration of the facts enumerated can leave no doubt that it was to a relative 
deficiency of available potass that the falling off, not only in the total weight of produce, 
but also in the description, and in the character of development, of the herbage, is to 
be attributed. 
Notwithstanding the great reduction in the amount of produce, and in the amount 
of potass taken off in the crop, after the cessation of its application, there was still, in 
every one of the 14 years, much more potass taken up than without manure. There 
was, however, something like a gradual reduction of the excess from year to year, and 
it averaged not much more than half as much over the second as over the first seven of 
the 14 years. It is obvious, therefore, that the unexhausted residue of the potass 
applied during the first six years has, in a considerable proportion at any rate, remained 
in the soil within the range of the roots, but that only a limited and gradually decreasing 
proportion has been available each year. The questions arise—how much unexhausted 
residue did remain at the end of the six years of the application ? and whether the 
whole of it has as yet been yielded up ? In estimating the amount of unexhausted 
residue, we have first to consider whether the whole of the potass of the crop was 
derived from that which was artificially supplied, or whether only so much of it as was 
in excess of that taken up without manure? 
