EXPERIMENTS OX THE MIXED HERBAGE OF PERMANENT MEADOW. 307 
In reference to the striking effects of this smaller quantity of nitrate of soda alone, 
over a period of 18 years, during which, excepting in the item of soda, the growth was 
entirely dependent for mineral constituents on the supplies of the soil itself, it may be 
remarked that the same circumstances which were pointed out as serving to explain the 
better result with the larger amount of nitrate than with the ammonia-salts, obtained 
in even a rather greater degree where the smaller quantity of nitrate was used. Thus, 
a still greater total number of species grew ; a somewhat greater number of the grasses 
contributed to the bulk of the gramineous herbage; the tendency to form stem and seed 
was greater; the proportion in the produce of the non-gramineous herbage was greater, 
and it was made up of a greater variety of species. It is to be supposed, therefore, 
that the roots would have more complete possession of the soil and the higher layers 
of the subsoil. It has been seen, indeed, that they had sufficient command of them to 
take up nearly as much total mineral matter, and even rather more of the important 
constituents—lime, potass, and silica—than with the larger amount of nitrate. 
It would appear that the limit of growth under the influence of nitrate of soda 
alone—that is to say without the aid of any artificial supply of mineral constituents 
—was nearly reached with the smaller quantity used ; and a comparison of the results 
obtained by it with those by the double quantity led us to stop the application of tins 
after the twentieth year of the experiments, that is to say, after 18 years of its use. A 
mixed mineral manure, comprising sulphates of potass, soda, and magnesia, and super¬ 
phosphate of lime, has now been applied instead for four years, and it is jmoposed to 
continue the application with a view to determine what proportion, if any, of the 
hitherto unrecovered nitrogen of the excess of nitrate supplied will be recovered, and 
also to observe the changes in the flora, so to speak, under this change of treatment. 
So far, the indications are not in favour of the supposition that any material proportion 
of the previously unrecovered nitrogen of the nitrate will be recovered in subsequent 
crops; indeed, it would appear probable that much has passed away by drainage. 
The general character of the herbage, is, however, rapidly changing. The grasses show 
a much lighter colour, and much more tendency to form stem, and to mature ; 
leguminous species (especially Lathyruspratensis) are gaining ground; and the character 
of the miscellaneous herbage is also changing. 
4. Mixed Mineral Manure alone ; Plot 7. 
We have now to show the effects of a mixed mineral manure, such as just referred 
to, when applied to the complex herbage year after year without any nitrogenous 
manure. This experiment was commenced in the first year of the series, 1856, and 
has been continued up to the present time. 
The “mixed mineral manure” used, was composed, per acre per annum, as follows :— 
2 R 2 
