20 Garden Work 
which supply a greater or less amount of nitrates for the 
plants. 
PHOSPHATES 
There are many forms of this class of manure. Super- 
phosphate, however, is one of the principal, and is formed 
by treating certain mineral phosphates with sulphuric acid, 
thus making the phosphates more soluble and more readily 
available for plant food. We must, however, be careful 
in the application of such acid manures, as we have pre- 
viously seen what happens when the soil becomes acid in 
reaction. We must see, therefore, that we have sufficient 
lime in the soil to neutralize the acids. Lime also com- 
bines with the superphosphates, and prevents them from 
being dissolved and washed out of the soil before they 
can be utilized by the plant as food, the plant afterwards 
taking up the phosphate slowly from the lime. Super- 
phosphate is naturally a quick-acting manure, that is, it 
is easily dissolved and made into food available for the 
plants. 
Then we have the various forms of bone manure, which 
contain a large proportion of phosphate. They are, how- 
ever, very slow in action, and should be applied where 
slow but sustained action is required, such as when young 
fruit trees are planted, when lawns are being formed, &c. 
Then there are crushed -bone manures, bone meal, and 
steamed bone flour. The fineness of these various manures 
will be a guide to the method of their application. 
We have also basic slag, which is a slow-acting phos- 
phatic manure, and which contains a large proportion of 
lime. Now, for a heavily manured garden ground, this 
