more than half what it is where
double the quantity was used. Again, on plot 13, 200 lbs. of Peruvian
guano per acre, gives nearly as great an increase of sound corn, as the
150 lbs. of sulphate of ammonia. Now, 200 lbs. of Peruvian guano
contains nearly as much ammonia as 150 lbs. sulphate of ammonia, and the
increase in both cases is evidently due to the ammonia of these manures.
The 200 lbs. of Peruvian guano, contained about 50 lbs. of phosphate of
lime; but as the sulphate of ammonia, which contains no phosphate of
lime, gives as great an increase as the guano, it follows, that the
phosphate of lime in the guano, had little, if any effect; a result
precisely similar to that obtained with superphosphate of lime.

"We may conclude, therefore, that on this soil, which has never been
manured, and which has been cultivated for many years with the
_Ceralia_--or, in other words, with crops which remove a large quantity
of phosphate of lime from the soil--the phosphate of lime, relatively to
the ammonia, is not deficient. If such was not the case, an application
of soluble phosphate of lime would have given an increase of crop, which
we have shown was not the case in any one of these experiments.

"Plot 10, with 400 lbs. of unleached wood-ashes per acre, produces the
same quantity of _sound corn_, with an extra bushel of 'nubbins' per
acre, as plot 1, without any manure at all; ashes, therefore, applied
alone, may be said to have had no effect whatever. On plot 3, 400 lbs.
of ashes, and 100 lbs. of plaster, give the same total number of bushels
per acre, as plot 2, with 100 lbs. of plaster alone. Plot 8, with 400
lbs. ashes, and 150 lbs. of sulphate of ammonia, yields three bushels of
sound corn, and five bushels of 'nubbins' per acre, _less_ than plot 4,
with 150 lbs. sulphate of ammonia alone. This result may be ascribed to
the fact previously alluded to--the ashes dissipated some of the
ammonia.

"Plot 11, with 100 lbs. of plaster, 400 lbs. ashes, 300 lbs. of
superphosphate of lime, and 200 lbs. Peruvian guano (which contains
about as much ammonia as 150 lbs. sulphate of ammonia), produced
precisely the same number of total bushels per acre, as plot 4, with 150
lbs. sulphate of ammonia alone, and but 4 bushels more per acre, than
plot 13, with 200 lbs. Peruvian guano alone. It is evident, from these
results, that neither ashes nor phosphates had much effect on Indian
corn, on this impoverished soil. Plot 14 received