14 MARKET GARDENING 



the soil and with the character of the crop to be fertilized. 

 The amount varies from a few pounds to as much as 250 

 pounds per acre. It is the better practice to make smaller 

 and frequent applications rather than to make larger and 

 fewer applications. 



14. Other Sources of Nitrogen. Nitrogen may also be 

 obtained from the use of dried blood, tankage, manures, 

 raw or steamed bone and ground fish. Dried blood decom- 

 poses quite rapidly and its supply of nitrogen becomes 

 available quickly. Tankage decomposes somewhat more 

 slowly than does dried blood. Manures, raw bone and 

 steamed bone decompose slowly. Ground fish becomes 

 available slowly. 



The supply of nitrogen in a complete fertilizer should 

 have at least two sources, nitrate of soda, and another source 

 such as dried blood or tankage. 



16. Potash. Potash is particularly necessary in grow- 

 ing root croops, as carrots, turnips, beets, radishes, and 

 parsnips. It is also important in growing other vegetable 

 crops. Sandy or muck soils are usually very deficient in 

 their supply of this element. 



Potash is obtainable in several forms, muriate of potash 

 being the most available form. Sulphate of potash is also 

 a desirable form. 



17. Phosphoric Acid. As most soils are deficient in 

 phosphoric acid, the gardener must supply this element 

 of plant food in some form. Phosphoric acid is very impor- 

 tant in the growth of nearly all vegetable crops, the cereals 

 being particularly benefited by it. A deficiency of phos- 

 phoric acid is indicated by small yields and the slow maturity 

 of the crops. 



Phosphoric acid is derived from several sources, the most 

 important being Rock Phosphate, Thomas Slag, raw and 



