640 Abstract Report of Agricultural Discussions. 
of skill, care, and deliberation, involving great expense, which 
renders them extremely valuable. I speak strongly on this subject, 
because I think the merits of the researches of Messrs. Lawcs and 
Gilbert have scarcely met with the amount of recognition from the 
great body of agriculturists and from scientific men to which they are 
entitled. The longer I live, the more deeply am I convinced of the 
necessity of carrying out in our fields experimental researches, similar 
to those which have been conducted for so many yeai's at Rothamsted. 
The grass experiments which have been carried on in the home park 
are especially valuable ; and -I only wish I could take my audience 
down to the field, and give them a field lecture there, instead of having 
to direct their attention to diagrams and to a few specimens which I 
was so fortunate as to secure yesterday evening, and have brought 
with me this morning. I hope, however, to be enabled to show the 
meeting how a certain description of manure fosters certain species 
of plants, and how it like\\dse increases the total quantity of produce. 
Tlie most valuable manuring substances are the following : — First, 
nitrogen, either in the shape of ammoniacal salts, or in that of nitrates, 
and organic matters capable of jiroducing on decomposition either 
nitrates or ammonia : secondly, the phosphates ; and, thirdly, the 
alkalies. These are the most important ; but we have also to con- 
sider the eflects of lime and silica. What, then, are the effects of 
ammonia upon grass land ? These, in the first place, vary according 
to the presence or absence of available minerals, — that is to say, with 
the quality of the soil. If there is an abundance of vahiable mineral 
matter, and if this be present in an available condition — that is to 
say, in such a state of combination that it can be taken up by the 
roots of the plants — then ammoniacal manures are very valuable indeed, 
for they promote a very luxm-iant development of the herbage. But 
if the mineral constituents — the phosphates, the salts of lime, the 
alkalies, and the soluble silica — are deficient, by the application of 
ammoniacal manures alone we should deteriorate the quality of the 
herbage, and ■nithin a very few seasons there would be no very largo 
imi^ression visible in its quantity. The diagram before you states 
that the produce of the mimanurcd portion of the laud at Eotham- 
sted has amounted to about 1 ton 6 cwts. The ammoniacal salts 
alone have not increased the jn-oduce nearly so much as when given in 
conjunction with minerals. The i^roduce in the latter case is nearly 
treble that in the former. The addition of ammonia even to farmyard 
manure produces a striking effect. The latter contains but little 
ammonia in comparison with the amount of mineral matter and 
carbonaceous matter there present. To dispose at once of the car- 
bonaceous substances — organic matters free from nitrogen, and con- 
taining chiefly carbon and hydi'ogcn with some oxygen, — I Avould say 
that in Mr. Lawes's expei'imcnts I have found scarcely any effect from 
them either on the quality or the quantity of the produce. In 
farmyard-manure it is not so much the carbonaceous clement which 
tends to increase produce as tlie nitrogenous and mineral portion. 
But the specimens which I have brouglit here this nu)rning aro 
better calculated than these remarks to give you an idea of tho 
