MINERAL COMPOSITION OF CROPS 21 



This fact has encouraged the study of soils in these areas, and many 

 references in the literature describe the materials from which the 

 soils were developed and the relation of these geological differences 

 to the occurrence of disease. Unfortunately, however, in only a 

 very few instances were the soils studied and described by competent 

 soil scientists. Most of the descriptions give insufficient information 

 about the true soils for their proper classification, and it is almost 

 certain that many of the apparent anomalies could have been resolved 

 with the aid of a competent soil taxonomist. 



In general, it has been found that the low, poorly drained lands of 

 the humid coastal regions, the moors, and the peaty soils are associ- 

 ated with bone diseases. Other physiographic regions are not free of 

 soils on which these diseases occur, for many of the mineral soils over 

 the entire world are deficient in nutrients, or, because of climatic 

 conditions, fail to supply sufficient quantities of available nutrients 

 essential to plant and animal life. Investigations of the forage grow- 

 ing on these soils indicate that two factors operate to prevent the 

 animal from obtaining adequate supplies of minerals. (1) The pasture 

 flora of fertile soils often are quite different from those of infertile 

 ones on which the acid-loving plants of low nutritive requirements are 

 able to crowd out plants such as the Leguminosae that require more of 

 the nutritive elements. (2) Actual differences occur in the compo- 

 sition of the plant, and studies such as that of Greaves and Greaves 

 {219) show that these variations have an important bearing on the 

 health of the animal. 



Nutritional anemias ascribed directly or indirectly to deficiencies 

 of some of the minor elements such as iron, copper, and cobalt have 

 been found to occur on many soils in the United States, New Zealand, 

 Australia, and other countries. In both the Kenya Colony and 

 New Zealand many of the soils have developed on erupted volcanic 

 materials. These volcanic showers usually lie upon porous sand- 

 stones or loose sands in the abnormal regions and upon limestone in 

 the normal regions, and many of these soils show some podzolization. 

 In Florida the disease has been observed on the white or gray sands 

 such as the Leon fine sand, Everglade mucks, and the young, poorly 

 drained soils developed from marl in the vicinity of Homestead. 



References to osteomalacia and anemia in human beings that may 

 be correlated to the soil are few, but studies in Florida indicate that 

 a nutritional anemia in children has been correlated with the soils 

 from which the children derived the major portion of their food. 



The causes of some nutritional diseases such as licking disease 

 have not been well defined, although in some areas, at least, copper is 

 said to be the limiting factor. Whatever the cause of this disease, 

 descriptions of soil parent materials are often made, and, although 

 true soil descriptions are lacking, some distinctive differences between 

 deficient soils and normal soils have been noted. Thus, the soils in 

 abnormal regions were often found to be developed from granites or 

 mottled sandstone, whereas those in normal regions were developed 

 mostly from gneiss, a potash-bearing rock, and in general, deficient 

 soils were described as low moor soils or very light sands. A vast 

 amount of work has been done in Europe on the composition of forages 

 in connection with the occurrence of licking disease. 



