for Twentij Years in succession on the same Land. 2S7 
pliospliate of lime and sulpliate of potass (that is excluding sul- 
phates of soda and magnesia) ; and Plot M has received super- 
phosphate, and sulphates of soda and magnesia (that is excluding 
sulphate of potass). 
The mixture of superphosphate and potass-salt has given an 
annual average of slightly more corn, but no more straw, than 
the superphosphate and soda and magnesia salts, without potass. 
The produce by both manures has fallen off over the later as com- 
pared with the earlier years, so far as corn is concerned ; but by 
that including potass it has done so more than by the one without 
it; and whilst by the manure containing potass, the produce of 
straw also has fallen off, that by the soda and magnesia without 
potass has even increased in straw during the later years. Taken 
over the whole period, the mixture of superphosphate and potass- 
salt has given annually about 1,V bushel more corn, but only 
exactly the same amount of straw, as that with soda and magne- 
sia, but without potass. The crop was, however, in both cases 
most miserable; in the one only 22|, in the other only 21^ 
bushels of corn, and in both only 12^ cwts. of straw. 
It may be concluded that there was in neither case any defi- 
ciency of mineral matter for such meagre crops ; but that in the 
one the relatively liberal supply of potass favoured seeding ten- 
dency, and in the other the salts of soda and magnesia, whether 
by action on the soil, or more directly on the development of the 
plant itself, favoured some increase of plant, without corresponding 
seeding tendency. Evidence of the effects of superphosphate 
and potass-salts, compared with superphosphate, potass, soda, 
magnesia-salts will be forthcoming when the results obtained 
with these mixtures in conjunction with nitrogenous manures 
are considered. 
It will be of interest to compare the effects of purely mineral 
manures on wheat, and on barley. The following Table (XXX.) 
shows the effects of the same "mixed mineral manure," used over 
the same period of 20 years, with the two crops. As in the case 
of the experiment with farmyard manure, the produce, not the 
increase, of the two crops is taken for illustration, and, mutatis 
mutandis, for similar reasons. But it should be further explained, 
that whilst in the case of the wheat plot, 8 crops, variously but 
upon the whole liberally manured, had already been taken, in 
that of the barley the period commences with the first year of 
the experiments. 
As without manure, and with farmyard manure, so with the 
mixed mineral manures, barley yields considerably more grain 
than wheat — in fact, not far short of one-half more. On the other 
hand, it gives rather less straw, but of total produce (corn and 
straw together) considerably more than the wheat. It may be 
