1406 MESSRS. J. B. LAWES, J. H. GILBERT, ARD M. T. MASTERS, 
Calculation showed that a comparatively insignificant proportion of both the nitrogen 
and the mineral constituents estimated to he annually supplied in the dung was 
annually recovered in the increase of crop yielded; nor did the addition of the 
ammonia-salts increase the produce so much as might have been expected. It seemed 
desirable, therefore, to attempt to determine the degree, and the permanence, of the 
effect of the large amounts of the nitrogen, and of the mineral constituents of the 
manure, which were calculated not to be recovered in the increase of crop during the 
years of the application, the greater part of which, at any rate, must be supposed to 
exist as residue within the soil. Further, so far as there would be a relatively greater 
available residue of mineral constituents than of nitrogen, it was to be supposed that 
the application of the ammonia-salts would greatly accelerate the recovery of them. 
The main facts relating to the produce and the increase of the total mixed herbage 
over the first 20 years were considered in detail in Part I.; some reference was also 
there made to the amounts of the nitrogen, and of the mineral constituents, taken up, 
and these points will be more fully treated in. Part III. It is, however, necessary in 
order to render intelligible the conditions under which the botanical changes have 
taken place, that the general results as to the produce, and some of its constituents, 
should be briefly stated here; and we are now able to give them for 25 years, in five 
out of the last six of which second as well as first crops were removed, the tendency 
to exhaustion being thereby considerably accelerated. 
Whether we look to the period of the application of the farmyard manure, or to 
the succeeding periods of six, six, and five subsequent years of the action of the 
residue, there is a considerable increase compared with the unmanured plot; and there 
is further increase over each period by the action of the ammonia-salts. There was, 
however, on all three plots, a considerable reduction in produce during the second six 
as compared with the first six years after the cessation of the application of the dung 
on plots 2 and 1. Over the last five years, however, there was a slight excess of 
produce compared with that over the previous six, even reckoning the first crops 
only, and, including the second crops, there was a very considerably greater total pro¬ 
duce, both on the unmanured and on the manured plots, than over the preceding six 
years; and over the whole period of 25 years, there was nearly as much annual excess 
on the manured plots compared with the unmanured, as over the first 20 years. 
Much the same may be said of both the total mineral matter and the nitrogen taken 
up. Indeed, much more of the mineral matter has been annually removed in the first 
crops only, over the last five years, than over the preceding six, and including the 
second crops, very much more; in fact, annually more than over the first 20 years. Of 
nitrogen there was, including the first and second crops, more than one-third more 
annually taken off without manure, more on plot 2 with dung or its residue alone, and 
one-third more on plot 1 with the ammonia-salts in addition, over the last five, than 
over the preceding 20 years. It is obvious, therefore, that the removal of the second 
crops in the later years is, as before said, rapidly accelerating exhaustion, a fact which 
