on Permanent Meadow Land. 
5-25 
naceous ; and that the mixtures of mineral manure and ammonia- 
salts (or nitrate suppljing^ an equal amount of nitrogen), which 
gave a very much increased, and also an almost exclusively 
Graminaceous produce, gave also the highest yield of nitrogen 
in the series — even more than a mixture of farmyard-manure and 
ammonia-salts, together supplying much more nitrogen. 
The important question arises — What proportion of the nitro^ 
gen supplied in the manure is recovered as increased yield of 
it in the crop ? 
Proportion of the Nitrogen supplied in the Manure which is 
recovered as iticrcased yield of it in the Crop. 
In our former Report, with the average results over only three 
years before us, we showed that, under the most favourable con- 
ditions, the increased 3'ield of nitrogen in the hay- crop scarcely 
reached, and in the average of cases fell short of, 50 per cent, of 
that supplied in the manure. But it was admitted that three 
years was too short an experience upon which to form a satis- 
factory estimate gn the point. The calculations have now been 
made for the whole seven years of the experiments. 
In Table IX. (p. 538) are recorded the actual amounts of 
nitrogen per acre (lbs.), and in Table X. (p. 539) the amounts 
for 100 in manure, which were recovA'ed as increased yield of it, 
when known quantities were supplied, each being reckoned 
both over the yield without manure, and over that by mixed 
mineral manure alone ; and, for compaiison, the average results 
over both the last four and the whole seven years are given. 
It is obvious that, in a practical or economical sense, the only 
direct gain to the farmer of nitrogen in the produce by the use 
of mineral and nitrogenous manures together, is so much as is 
over and above the amount yielded by the same mineral manures 
when used alone. But, for reasons explained in our former Re- 
port, we deem it, upon the whole, the most consistent with what 
we know of the facts, to reckon at least so much of the nitrogen 
of the produce grown b}- nitrogenous manure as is over and 
above that yielded without manure, to have its source in the 
nitrogen supplied, whether the nitrogenous manure be employed 
alone, or in conjunction with mineral manure. 
Reckoned in this way. Table X. shows that, when am- 
monia-salts were used alone (Plot 4), 27-4 per cent, only of the 
nitrogen so supplied was recovered as increased vield over the 
seven years, and very nearly the same proportion, 27'1 per cent., 
over the last four years. With salts of ammonia and sawdust 
(Plot 5), reckoning of course the nitrogen in the sawdust, the 
proportion recovered was rather less, but again about equal over 
the seven and the last four years. With the smaller amount of 
T 
