Soluble vs. Insoluble Cane Manures 345 
effects of various nitrogenous substances. As regards 
rapidity of action, nitrate of sodium takes the first place, 
sulphate of ammonium the next, then follow dried blood, 
flesh meal, steamed bones, horn and wool waste, the 
various oil cakes, and lastly old leather. In nitrate of 
sodium the nitrogen is in a condition directly assimilable 
by plants (that is in the form of nitric acid), whilst in the 
other substances it has to undergo certain changes to 
make it fit for the purpose. There being as it were 
only one step between ammonia and nitric acid, ammo- 
nium salts speedily undergo the necessary change, but 
as already explained, this is of doubtful advantage as the 
nitrogen is then too readily washed out of the soil by the 
rainfall. Sugar cane is a plant that developes in suc- 
cessive distinct portions, — every joint grows and matures 
independently of every other joint, and it follows that 
if a supply of nitrogen is required for the first, so equally 
is it required for the last. Therefore manures that yield 
nitrogen in an assimilable form continuously and gra- 
dually during the entire growth of the cane, would be 
the most suitable. Nitrate of sodium and sulphate of 
ammonium do not appear to fulfil this condition. It is 
well known that their action is energetic at first, but 
soon ceases, and this is probably in consequence 
of their speedy removal from the soil in the drainage.* 
On the other hand, animal and vegetable nitrogenous 
matters undergo conversion into nitric acid slowly, yet 
sufficiently fast to keep pace with the requirements of 
* This rapid aftion has given rise to the curious notion that sul- 
phate of ammonium acts as a " stimulant." But a young plant does 
not need a stimulant any more than a baby does ; proper food only 
is required. 
