384 
MESSRS. J. B. LAWES AND J. H. GILBERT ON THE RESULTS OR 
—to reduce the complexity of the herbage, to render it more gramineous, to increase the 
amount of produce, and, with this, to draw more upon the mineral stores within the 
soil. It would, at the same time, appear, that where the ammonia-salts were applied, 
in amount supplying only 41 lbs. of nitrogen per acre per annum, the available supply 
of nitrogen was relatively higher than the available supply of some of the more 
important of the mineral constituents, more especially of potass and phosphoric acid, 
notwithstanding (to say nothing of the stores of the soil itself) the large residue of 
these estimated to have accumulated, and to remain, within the soil. 
It will be remembered it was estimated that, over the eight years of the application 
of the dung alone, only about 10^ per cent, of the supplied nitrogen Avas recovered as 
increase in the crop during that period, and that little more than 18 per cent, of the 
eight years’ supply was recovered in the 20 years. In a similar way, it was estimated 
that, over the eight years of the application of both the farmyard manure and the 
ammonia-salts, about 13 per cent, of the total nitrogen supplied was recovered, and 
over the 20 years—eight with dung and ammonia-salts, and 12 with ammonia-salts 
alone—about 21^ per cent.; or, if the increased yield of nitrogen with the ammonia- 
salts over that without them be assumed to represent the amount derived from them, 
it would result that about 271? per cent, of the nitrogen of the ammonia-salts was 
recovered, whilst only about 18 per cent, of that of the farmyard manure was recovered. 
If should be observed, however, that much more than 2per cent, of the nitrogen of 
ammonia-salts, or of nitrate of soda, is estimated to be recovered when these were 
employed in conjunction with an annual supply of soluble artificial mineral manures. 
There is thus, here, further evidence of the much less effect of a given amount of 
nitrogen supplied in farmyard manure than as ammonia-salts. It is also clear that, 
although the application of the ammonia-salts was the means of turning to account 
some of the accumulated residue of the mineral constituents supplied in the dung, the 
limit of the immediately available supply was very soon reached, the remainder be¬ 
coming less and less rapidly recoverable. It was, in fact, retained in a condition so 
slowly available as to be of but little effect in increasing immediate crops, and therefore 
of but little practical value, except as a storehouse against exhaustion. 
The Second Crops. 
So far, the produce of the first crops only, of each year, has been taken into account. 
As already explained (pp. 7 and 8), the second crops were, as a rule, fed off by sheep, 
having no other food, that they might contribute nothing in their manure that they had 
not derived from the land; whilst, having no other food, they sometimes even lost weight, 
especially in bad weather. They would, therefore, generally retain but little, and 
sometimes none at all, of either the nitrogen or the mineral constituents of the grass 
they consumed ; and they might even sometimes themselves lose something. On this 
