18 Subtropical Vegetable-Gardening 



Suppose that 2 per cent of the ammonia is wanted from 

 nitrate of soda and 3 per cent from cottonseed meal. We 

 proceed as before to read down the first colmnn to the 

 figure 2, and then across to the nitrate of soda column, 

 where we find the figure 220, which is the amount of nitrate 

 of soda needed. We then proceed similarly and find 

 800 pounds to be the amount of cottonseed meal needed 

 to make 3 per cent of ammonia. Then proceed to find the 

 amoimts of other elements as before. 



LIME 



A plant needs a certain amount of lime. There is often 

 sufficient in the soil as carbonate of lime or limestone. 

 Phosphate and land plaster contain a large percentage of 

 it. But the uses of lime in agricultural soils are usually 

 quite different from its use as a plant-food. It neutralizes 

 the acids which are produced in damp vegetable soils, 

 and is required for the growth of the bacteria which change 

 animal and vegetable matter into soluble salts on which 

 the plants can feed. Lime may be put on the soil as 

 ground limestone or as slaked lime. 



Ground limestone. 



The amount of ground limestone to be used will vary 

 greatly according to the acidity of the particular piece of 

 land, even different parts of the same acre showing different 

 degrees of acidity. A soil that is only slightly acid will 

 need from one to two tons of ground limestone ; soils that 

 are decidedly acid will require about twice as much ; and 

 some of our most acid soils will be benefited by as much 



