Experiments with different Top-dressings upon Wheat. 395 
wheat-crop. Indeed, I did not expect any increase from the 
aj)plication of this marl, and used it in this experiment chiefly to 
ascertain the extent of variation in the produce of two separate 
|;-acre plots. The result plainly shows that the experimental field 
was very uniform in its character and productiveness. We may 
also learn from this result that the efficacy of a manure is greatly 
affected by the chemical composition of the soil to which it 
is applied. However beneficial chalk-marl may be in other 
localities, it cannot possibly do any good on land which contains 
already an abundance of the same elements which are supplied 
in the marl. 
2. The application of only If cwt. of nitrate of soda raised 
the produce in corn to 38 bushels, and that of straw to 1 ton 
4 cwt. 8 lbs. We have thus here an increase of 11 bushels of 
corn, and 6j cwt. of straw, at an expense of 1/. 12s. 6rf. 
3. By mixing nitrate of soda with common salt, the produce 
in corn was raised to 40 bushels, and that of straw to 1 ton 
4 cwt. 1 qr. 20 lbs. It appears thus that the admixture of 
salt to nitrate of soda was beneficial in this experiment. The 
quantity of salt used amounted to only 1^ cwt. : notwithstanding, 
it had a decidedly beneficial effect upon the produce. As salt 
is cheap, it may be worth while to try in future experiments 
whether a larger dose of salt mixed with nitrate of soda will be 
of advantage. 
4. Peruvian guano produced very nearly the same quantity of 
corn as the mixture of nitrate of soda and salt, but somewhat less 
straw. 
5. The smaller dose of wheat-manure gave almost ^ a bushel 
less increase in corn, and rather more straw, than guano. The 
difference in the yield of these two plots, however, is trifling. 
6. The larger dose of Proctor's wheat-manure (6 cwt. per acre), 
it will be seen, gave an increase of 1 bushels of corn, and 9 cwt. 
1 qr. 12 lbs. of straw, over the yield of the unmanured plot. 
4 cwt. of the same wheat-manure gave an increase of 12J bushels 
of corn, 6 cwt. 12 lbs. of straw. One-half more of wheat- 
manure, or 6 cwt., very nearly gave one-half more increase in corn 
and straw. The chief points of interest which attach to these 
experiments are : — 
1. That nitrate of soda applied by itself materially increased 
the yield of both straw and corn, 
2. That the admixture of salt to nitrate of soda was found to 
be beneficial. 
3. i'hat guano produced as good a result as nitrate of soda. 
4. That the increase in corn and straw corresponded with the 
quantity of the wheat-manure which was used. 
5. That ammonia and nitrogenized organic matters — which 
