306 Report of Experiments on tlie Groidli of Barley, 
together ; leavin<:i:, of course, so much less to be reckoned as 
increase due to the action of the ammonia-salts. 
Reference has already been made to the probable or possible 
cause of the much greater produce of barley than of wheat by 
the mineral manure alone (p. 289). On this point it should be 
borne in mind that, for the wheat the mineral manures, as well 
as the ammonia-salts, are applied in the autumn, whereas for the 
barley both are applied in the spring. It is a question, there- 
fore, whether there be not a much greater dilution and distri- 
bution of the autumn-sown mineral manures by the winter rains ; 
a locking-up of some of their constituents in difficultly soluble 
combinations within the soil ; hence a less active root-deve- 
lopment in the upper and more highly nitrogenous layers of the 
soil when growth commences in the spring ; and hence, also, 
less luxuriance in the case of the wheat ; but, on the other hand, 
a more rapid exhaustion of the previously accumulated nitrogen 
within the soil by the barley. If this be so, the higher produce 
pi barley than of wheat by mineral manures alone is, in a sense, 
accidental, and may prove not to be permanent. In that case, 
the comparison of the actual produce will more fairly illus- 
trate the difference of effect of the mineral manure and a given 
amount of ammonia-salts applied to wheat and to barley, than 
will that of the mere increase over the produce by the mineral 
manure alone ; and the less amount of increase of barley than of 
wheat so calculated in these last experiments, will prove no 
exception to the conclusion arrived at from the results of the 
other experiments, namely, that a given amount of ammonia- 
salts applied in the spring for barley is more productive than an 
equal amount applied in the autumn for wheat. 
Briefly enumerated, the very important results, obtained by the 
use of nitrogenous and mineral manures together, are — that 
much more than the average barley crop of the country has been 
obtained for 20 years in succession on the same land, by the 
annual application, in the spring, of 200 lbs. of ammonia-salts, 
and cwts. superphosphate of lime ; that the addition of salts of 
potass, soda, and magnesia, gave no further increase ; and that 
the application, for the same period, of the same amount of 
ammonia-salts (with mineral manure) in the autumn, for wheat, 
gave nearly 37 per cent, less corn, nearly 14 per cent, less straw, 
and about 24 per cent, less total produce. The causes of the 
remarkable differences of result with wheat and with barley will 
be considered in Section IV. 
