1330 
MESSRS. J. B. LAWES, J. H. GILBERT, AND M. T. MASTERS, 
surface-soil becoming available under the influence of the mineral manure, it would 
hardly seem probable that the deeper-rooting plants would thoroughly regain their 
former position. 
With regard to the undoubted tendency to gradual increase, not only in the 
relative but in the actual amount of the grasses in recent years, the explanation may 
perhaps be open to question ; and the evidence bearing upon it will be considered more 
in detail in the chemical section of our report. As has been referred to, the growth of 
a leguminous crop on arable land, frequently leaves the surface soil richer in nitrogen 
in a degree determinable by analysis; and it is known that after the removal of a 
highly nitrogenous leguminous crop a larger gramineous one, taking up more nitrogen 
than if it had succeeded another of the same description, will be obtained. It has been 
already suggested, whether the increased growth of the grasses here, in the mixed 
herbage, is due to similar conditions being induced by the increased growth of the 
Leguminosse, now in association, instead of separately in alternation, with them; 
that is, whether it be due to a residue of combined nitrogen left after the growth of 
the leguminous plants in such condition of combination and distribution as to be now 
available for the associated gramineous ones, the subsequent growth of which is 
thereby enhanced. Another explanation obviously may be, that under the influence 
of the mixed mineral manure, including potass, the richer nitrogenous accumulations 
of the surface soil of the grassland itself, yield up their stores in a condition in which 
the Graminese as well as the Leguminosse of the mixed herbage can take them up. 
Against this supposition is the fact, that such a potass manure will increase the growth 
of Legumimosae in the poorer in nitrogen ordinary arable land, whilst it will not, in 
any marked degree, increase the growth of the Graminese on such arable land. If, 
therefore, the result be due to the direct liberation, in an available form, of nitrogen 
from the resources of the soil itself, under the influence of the mineral manure, it 
would seem that it must be provided in different conditions of combination for these 
two very distinct descriptions of herbage, and that a supply in the condition required 
by the Graminese is in a very much greater degree available from the richer in nitrogen 
pasture, than from the poorer in nitrogen arable, surface soil. 
5. Superphosphate of lime , alone; Plot 4-1. 
The experiment with superphosphate of lime alone did not commence until the 
fourth year; sawdust alone, but without effect, having been applied in each of the 
first three years. It has been seen that in the case of the mixed mineral manure of 
plot 7, very marked results were produced, but from the complex character of the 
manure, it is only by comparison with those on other plots, and by other collateral 
evidence, that it can be decided to which of the constituents of the mixed manure the 
specially characteristic results were mainly due. Hence it is of considerable interest 
to compare the results obtained with superphosphate of lime alone with those from 
the mixed mineral manure, which included, besides the same amount of superphos¬ 
phate, salts of potass, soda, and magnesia. In the next sub-section will be compared 
