2 MISC. PUBLICATION 3 6 9, U. S, DEPT. OF AGRICULTURE 



attention in both popular and scientific literature dealing with soils, 

 fertilizers, plant growth and composition, food quality, and animal 

 and human health and nutrition. 



It is also significant that greater and greater emphasis is being placed 

 upon the problem of the interrelationships among these fields of inves- 

 tigation. It is believed, and the evidence will be cited in this review, 

 that many nutritional diseases are caused by deficiencies or excesses of 

 particular minerals in food plants grown hi different soils, in different 

 localities, and with different cultural practices. Although there is 

 abundant evidence, as shown by this literature survey, that these 

 relationships are real and profound, the data are wholly insufficient 

 for defining such relationships in definite practical terms that can be 

 translated into recommendations for agricultural practice on specific 

 soils for the culture of specific food plants. Aside from the fact that 

 the many unsolved aspects of this problem are certainly responsible 

 for much poor nutrition and poor husbandry, this kind of situation is 

 leading to all sorts of conjecture on the part of the public and to many 

 unwarranted claims in regard to the special advantage or disadvantage 

 of certain soils, fertilizers, and food plants. The Department of 

 Agriculture does not have the necessary facts to judge all of these 

 claims. 



It is not the purpose of this review to discuss animal nutrition, 

 plant physiology, pedology, or other disciplines closely related to 

 this general problem, as such. It cannot be held to be within the 

 scope of any one worker's experience or capabilities to venture to dis- 

 cuss the special techniques in such a broad variety of fields. Further- 

 more, within each field, certain facts are well known or appreciated, 

 and it is neither necessary nor desirable to repeat or duplicate the 

 readily available surveys that have already been made. For example, 

 remarkably complete bibliographies on the minor elements and on the 

 relation of mineral deficiencies to animal diseases are available {486, 

 589, 595). 3 A few surveys of the role of minerals in plant or animal 

 nutrition have been made (87, 88, 168, 194, 243, 295, 305, 360, 388, 405, 

 410, 412, 439, 4^4, 605), but the discussion in these surveys centers 

 generally around the requirements of plants and animals for minerals. 

 Orr (443) has made a survey of pasture research in the British Empire 

 relating to the composition of herbage and the health of the animal, and 

 brief reviews of the importance of soils in the United States to human 

 and animal nutrition have been made by Maynard (402), Beeson and 

 LeClerc (53), Browne (93), and Auchter (36). 



In the investigation of any nutritional disorder in plants or animals, 

 the difficulties of identification of the cause of that disease multiply as 

 the mobility of the subject increases. Thus, a plant, being stationary 

 as far as its orbit of activity is concerned, represents a relatively 

 simple subject for investigation. Any discrepancies or abnormalities 

 in its growth or appearance can be readily discerned and checked 

 against its source of nutrients, the soil. As a result, the effects of more 

 than 40 elements on the growth and health of plants have been 

 investigated and are more or less known. 



The typical domestic animal is, likewise, confined to a relatively 

 small area, particularly in modern times. The animal apparently 



3 Italic numbers in parentheses refer to Literature Cited, p. 59, and such numbers followed by "x" refer 

 to Sources of Unpublished Material, p. 91. 



