38 



MISC. PUBLICATION 3 69, U. S. DEPT. OF AGRICULTURE 



in the surface horizon, while a soil in Teton County, Mont., contains 

 only 0.2 p. p. m. Examination of the vegetation from the Hawaiian 

 soil showed that none contained more than 1 p. p. m., while Astragalus 

 pectinatus growing in the Montana soil contained 190 p. p. m. of 

 selenium. 



Boron has been studied quite extensively, both because of its 

 injurious effect and its essentiality for plant growth. The boron 

 contents of leaves of citrus trees suffering from a disease was shown by 

 Kelley and Brown {312) in 1928 to be several hundred times as high as 

 those of healthy trees. They stated in this connection: 



The results of this investigation strongly indicate that boron is readily absorbed 

 by citrus and walnut trees and that this element tends to accumulate in the leaves 

 of these species. Because of this fact, a determination of the boron content of 

 the leaves affords a valuable indication as to the boron conditions of the soil. 



They concluded that irrigation water is responsible for some diffi- 

 culties with boron, and Eaton (160) in 1935 supports this when he 

 states: 



Notwithstanding evidence of the occasional occurrence of appreciable con- 

 centrations of boron in unirrigated soils in the San Joaquin Valley, the general 

 inference to be drawn from the appearance of crops is that boron carried by 

 irrigation water is for the most part responsible for such depression in yield and 

 such crop injury as have occurred. 



Eaton further concludes that "much of the boron found in soils, 

 whether irrigated or not, is not very soluble." 



Woodbridge (598) in 1937 found that "a low boron concentration in 

 tissues can be correlated with high incidence of disease [of apples]. 

 A correlation between low boron in the soil and incidence of disease 

 was not established." 



Definite relationships between manganese in the soil and that in the 

 plant are few. Wester (586) in 1923 determined manganese in several 

 soils in the Netherlands along with that in digitalis leaves growing in 

 the soils. His data are given in table 17. 



Table 17. — Manganese in some Netherland soils and in digitalis leaves growing 



thereon 







[Wester (586)] 











Material 





Mn per 100 gm. of dry matter in — 





Noordwyk 



Delft 



Haag 



Soil 



2.4 

 .94 



14.4 

 1.32 



10 



Digitalis leaves . _ . . _______________ 



2.57 







Carlyle (106) in 1931 determined the manganese contents of several 

 plants grown in pots containing different Texas soils. He reported 

 differences of 200 to 500 percent in the manganese content, according 

 to the soil used. 



Leeper (340) stated that "manganese deficiency disease is confined 

 to soils of pH 6.7 or more and occurs especially on heavily limed 

 podzols." 



Iodine has been extensively discussed in relation to the occurrence 

 of goiter, but it is interesting to note that McHargue (377) in 1933 

 reported 250,000 p. p. b. of iodine in one sample of corn, whereas 18 

 other samples from other soils in Kentucky contained from 98 to 650 



