FERTILIZERS AND MANURES FOR THE ORCHARD 187 



is necessary for tree growth, the relative necessity of their 

 appUcation to the soil will depend on the amount already 

 available and the quantity taken up by any given kind of 

 plant. There has been much misunderstanding and erroneous 

 teaching regarding this question in pomology. However, 

 the field experiments have done much to clear up the situa- 

 tion, although there is still a lack of conclusive information. 



157. Organic versus inorganic fertilizers. — In compar- 

 ative tests on the use of organic fertilizers, such as dried 

 blood, tankage, and cotton-seed meal, and such inorganic 

 materials as nitrate of soda, acid phosphate, basic slag, and 

 nmriate or sulfate of potash, the conclusion is reached that 

 the inorganic materials are usually to be preferred. 



In an Ohio experiment ^ two orchards badly in need of 

 nitrogen show the following results as a five-year average 

 in pounds of fruit to a tree: 



Table LVI 



comparative valxje op inorganic and organic forms of fertilizer 



(after ballou) 



158. Value of nitrogen. — One of the most outstanding 

 results of the various fertilizer experiments conducted 

 throughout the country is the importance of applying ni- 

 1 Ohio Agr. Exp. Sta. BuU. 30L 1916. 



