MANURES AND FERTILIZING MATERIALS. 63 



phosphoric acid and potash. These three elements 

 are called "the essential elements" for two reasons: 

 First, because they are the elements which are removed 

 in greatest amounts by the harvesting of crops, and 

 secondly, they are present in smaller amounts in the 

 soil than the other elements. The other elements 

 which are needed for the growing crops are usually 

 present in sufficient quantities in the air and the soil 

 but sometimes it is necessary to add lime to the soil. 



Nitrogenous Fertilizers. This is a name applied 

 to the fertilizers which are rich in nitrogen. Cotton- 

 seed meal, nitrate of soda, sulphate of ammonia, fish 

 scrap and tankage are the principal nitrogenous fer- 

 tilizers sold. 



1. Cotton-seed Meal. This is the by-product from 

 the manufacture of cotton-seed oil. It consists of the 

 ground kernel or meat of the cotton seed, from which 

 most of the hulls are removed and the oil extracted. 

 It has a bright yellow color and is somewhat coarser 

 than flour. It is variable in composition, depending 

 on the amount of hulls present containing from 5 to 7 

 per cent, of nitrogen. It is a good fertilizer for crops 

 having a long growing season and is especially adapted 

 for the general southern crops. 



2. Nitrate of Soda. This substance is obtained 

 from the west coast of Chili. It is sometimes called 

 " Chili Saltpetre." It is a salt, but it is coarser and 

 of. a yellower color than table salt and contains about 

 15 per cent, to 16 per cent, nitrogen, or about twice as 

 much as cotton-seed meal. In the North it is used a 

 great deal for fertilizing cereals (wheat, oats, rye and 

 barley). It is also used to a great extent by market 

 gardeners all over the country to force their crops for 

 early market. It is soluble in water and for this rea- 

 son it should be applied a little at a time. It has the 

 tendency to produce quick growth. 



3. Sulphate of Ammonia. This is a by-product 

 obtained in the manufacture of illuminating gas. It 

 looks much like table salt and contains about 20 per 



