362 
MESSRS. J. B. LAWES AND J. H. GILBERT ON THE RESULTS OF 
per cent, in its dry substance, more phosphoric acid, considerably more potass, and 
rather more magnesia, than that of either plots 19 or 20. On the other hand it con¬ 
tained, both per acre and per cent., less lime than that of either of the other plots, 
and at the same time less soda and chlorine than that of plot 19 ; but that of plot 20, 
with nitrate of potass, but without soda in the manure, contained very much less soda 
than that of either plot 16 or 19 with it. The produce of plot 20 again, contained 
less of sulphuric acid, chlorine, and silica, than that of plot 19 ; but more of lime, and 
especially more of potass, both per acre and per cent. These differences are, so far as 
they go, also consistent with a more advanced condition of maturity of the produce of 
plot 20. 
There is, then, so far, no marked difference in the amount, or in the botanical compo¬ 
sition, of the produce, whether the nitrogen and the potass be supplied as nitrate of 
soda and sulphate of potass, or as nitrate of potass ; but the data at command as to 
the chemical composition would indicate a somewhat more matured condition of the 
produce grown by the nitrate of potass. 
16. Mixture, supplying the Asli-constituents, and the Nitrogen, of 1 ton of Hay; 
Plot 18. 
We have the results of one more experiment with artificial or chemical manuring 
substances to give in this section—those obtained on plot 18. Commencing in 1865, 
there has been applied annually to this plot, a mixture containing the quantities of 
potass, soda, lime, magnesia, phosphoric acid, silica, and nitrogen, contained in 1 ton 
of hay. The mixture also supplied sulphuric acid and chlorine in abundance. The 
object of the experiment was, in part, to put to the test of direct experiment the prin¬ 
ciples of manuring put forward by Liebig, according to which all the constituents, 
neither more nor less, which we remove in crops, should be returned to the soil. He 
says :— 
“By an exact estimation of the quantity of ashes in cultivated plants, growing on 
various kinds of soils, and by their analysis, we will learn those constituents of the 
plants which are variable, and those which remain constant. Thus also we w T ill attain a 
knowledge of thequantities of all the constituents removed from the soil by different crops. 
“ The farmer will thus be enabled, like a systematic manufacturer, to have a book 
attached to each field, in which he will note the amount of the various ingredients 
removed from the land in the form of crops, and therefore how much he must restore 
to bring it to its original state of fertility. He will also be able to express in pounds’ 
weight, how much of one or of another ingredient of soils he must add to his own laud, 
in order to increase its fertility for certain kinds of plants.” (“Agricultural Chemis¬ 
try,” 4th ed., pp. 212-213.) 
He further says as to the object of manuring : — 
“ This purpose is the restoration, or an increase of the original fertility, and by 
manure we must replace all the constituents of the plants which have been taken 
