Experiments with different Top-Dremnf/fs upon IVlieat. 107 
3. In the third experiment 2 cwt. of nitrate of soda and 
4 cwt. of salt gave scarcely a larger increase than in the fourth 
experiment, in which 2 cwt. of nitrate of soda was used alone. 
This was also the case in my wheat experiments in 1861 ; whilst 
in the preceding years of I860 and 1859 the addition of salt to 
the nitrate of soda had a marked beneficial effect upon the wheat 
crop. 
4. Salt alone, applied at the rate of 3 cwt. per acre, it will be 
seen, produced as large an increase as 1 cwt. of nitrate and 
2 cwt. of salt. 
This is a curious result, but it stands not solitary, for in 1861 
salt alone produced an increase of nearly 7 bushels of corn. But 
as salt alone in the years preceding 1860 had hardly any effect 
upon the increased production of corn, it appears very desirable 
that further experiments with this cheap fertilizer should be 
made. 
5. Peruvian guano, applied at the rate of 2 cwt. per acre, 
produced nearly as good a result as 2 cwt. of nitrate of soda. 
6. The addition of salt to the guano, it appears, had little 
effect in further increasing the produce in corn, as it had in 
conjunction with nitrate of soda. 
This is the more remarkable, since salt alone had such a 
favourable effect when used bv itself. 
7. Salt, added both to guano and to nitrate of soda appears to 
have checked over-luxuriance in the straw. Thus it will be seen 
that whilst 2 cwt. of nitrate of soda produced an increase of 
nearly 12^ cwt. of straw, the same quantity of nitrate mixed 
with 4 cwt. of salt gave only an increase of 9f cwt. of straw in 
round numbers. And again, whilst 2 cwt. of Peruvian guano 
gave cwt. of increase in straw, the same quantity of guano 
mixed with 2 cwt. of salt produced only an increase of 7 cwt. of 
straw. To show the commercial results I have constructed the 
following table, p. 108. The wheat is valued at 485. a quarter, 
the price at which it was actually sold, and the straw at 30,?. per 
ton, as a usual selling price. 
As regards economy, there can thus remain no doubt that 
nitrate of soda, as well as Peruvian guano, either alone or mixed 
with salt, may be used wdth great benefit as top-dressings for 
wheat, — at least, on calcareous soils which, like our soils, contain 
an abundance of mineral plant-food. 
^ On light land, guano and salt appear to me preferable to 
nitrate of soda or salt, because guano supplies phosphates and 
alkalies, as well as nitrogenized matters, whilst nitrate of soda 
is efficacious as a manure solely in virtue of its nitrogen. 
Caution ought, therefore, to be used in applying this salt as 
a top-dressing for wheat on light land. The opinion that nitro- 
genous 
