EXPERIMENTS ON THE MIXED HERBAGE OF PERMANENT MEADOW. 353 
The table shows that whilst with the ammonia-salts alone every year the average 
annual produce of hay was nearly one-third less over the last seven than over the first 
13 years, it was even rather higher over the last seven years than over the previous 13, 
where (on plot 6) the mixed mineral manure had been substituted for the ammonia- 
salts. Still, the amount of produce did not nearly reach that yielded on plot 7, where 
the same mixed mineral manures had been applied every year of the 20. 
In the amount of nitrogen annually taken off there was a considerable reduction 
over the last seven compared with the first 13 years, both where the application of the 
ammonia-salts was continued, and where the mixed mineral manure was substituted. 
But it is significant that there was nearly as much annually taken up where the appli¬ 
cation of ammonia-salts had been stopped, and mineral manures applied instead, as 
where the ammonia-salts were still applied. In neither case, however, was there as 
much nitrogen taken up as over the same seven years where no nitrogenous manure, 
but the mixed mineral manure alone, had been applied from the commencement. 
The reduction in the amount of mineral matter annually taken oft’ was, where the 
ammonia-salts were continuously applied, very much greater than that of either the 
hay or the nitrogen. On the other hand, where the mineral manures were substituted 
there was even rather more mineral matter taken up over the seven years of their appli¬ 
cation than previously. But, as in the case of the produce yielded, and of the nitrogen 
removed, so also in that of the mineral matter, there was much less annually taken 
up than where the same mineral manures had been annually applied over the whole 
period. 
With regard to the nearly equal amount of nitrogen taken up where the mineral 
manures succeeded the ammonia-salts, as where the nitrogenous manure was still 
applied, the question suggests itself—whether the result was merely due to the 
gathering up by the herbage already prevalent, of the unexhausted residue of the 
nitrogen of the previous applications—or, whether to the development of different 
plants, having more extended root-ranges, or different powers of collection from 
natural sources ? For certainly it was due to the latter causes that where, as on 
plot 7, mineral without any nitrogenous manures were applied every year, there was 
yet yielded, over the 20 years, even rather more nitrogen in the produce than was 
obtained on plot 5, where 82 lbs. of nitrogen were applied per acre annually. It will 
be remembered that the surface-soil of the continuously mineral-manured plot showed a 
lower percentage of nitrogen than that of the continuously unmanured plot, indicating 
the source whence the increased yield of nitrogen in the mineral manured complex 
herbage had been derived. 
The data at command do not enable us to give a decisive answer on these points, 
but it will be of interest briefly to notice the facts bearing upon them. 
In the first place, not quite three-fourths as much nitrogen was taken oft in the 
total produce of plots 5 and 6, during the 13 years of the application of the ammonia- 
salts to both, as was contributed by the manure during that period. And if we deduct 
MDCCCLXXX. 2 Z 
