FERTILIZING 1 07 



Iron. Very little is known of the part that iron plays in plant 

 metabolism, although it is required in small amounts by all plants. 

 It was formerly thought to be a constituent of chlorophyll, but this 

 was shown by Molisch l not to be true. Its presence is, however, still 

 considered indispensable to the formation of chlorophyll, its action 

 apparently being one of conditioning the nature of protoplasmic 

 activity. A small portion of the iron in plants is apparently held in 

 the form of organic compounds, possibly entering into the structure 

 of the chloroplastids. 



As a fertilizer, Ville 2 reports that a spray of 2-per-cent solution 

 of iron sulphate upon young apples and pears hastened the ripen- 

 ing and enlarged the fruits. To the writer this seems rather fanci- 

 ful, though a serious attempt has been made to explain it on the 

 ground of stimulation of the protoplasm and increased production 

 of chloroplasts in the epidermis. 



The value of iron applications to the soil in increasing the color 

 of fruit, especially of apples, has been the subject of considerable 

 discussion and some experimenting among horticulturists. The 

 amount of iron in the annual draft of apple trees (as shown in the 

 table on page 10 1) is worthy of note. But this mineral is probably 

 always available in required amounts in any agricultural soil, so 

 that additional applications could scarcely be expected to have any 

 marked direct influence. 



What to use. It is impossible to give definite advice in regard 

 to the best fertilizers for all kinds of soils. The poorer soils need 

 a greater amount than the more productive soils of all the ingredi- 

 ents mentioned, but especially of nitrogen. Requirements, how- 

 ever, will vary with the variety of apple grown or some other factor. 

 Voorhees 3 recommends a basic formula of equal parts of muriate of 

 potash, acid phosphate, and fine ground bone, with the addition of 

 nitrogen in the form of either barnyard manure or nitrate fertilizers, 

 or secured through leguminous cover crops. 



Professor Sears 4 recommends a fertilizer consisting of 1 ounce 

 of nitrate of soda, | pound of high-grade sulphate of potash, 



1 Hans Molisch, scientist, Zeltgasse 2, Wien, Austria. 



- Georges Ville, scientist and author, Le Grand Bilbarteault, France (1S76). 

 8 E. R. Voorhees, ex-director of New Jersey Agricultural Experiment Station. 

 4 F. B. Sears, pomologist, Massachusetts Agricultural College. 



