148 



THE PEANUT— THE UNPREDICTABLE LEGUME 



would be needed for the production of good quality peanuts in soils high 

 in organic matter or in those containing a large percentage of 2 : 1 type 

 miijerals. 



Studies by Mehlich and Reed (73) of a number of surface soils from 

 the Coastal Plain areas of North Carolina have indicated that the cation- 

 adsorption capacity due to organic fraction of the colloids varied between 

 8 and 70 percent of the total. Such differences in the nature of the col- 



type of colloid 

 Okaolin 



^bentonite 



■ organic 



(O 



> 



< 

 (J 



b2 



m 



m 

 1 





a 



0.38 M. E. 





1.30 M. E. 



2.40 M. E. 



EXCHANGEABLE CALCIUM 

 CATION -ADSORPTION CAPACITY 2.4 M. E. 



Figure 8. — The effect of the type of soil colloid on peanut fruit quality at different 

 levels of exchangeable calcium. The percentage of filled cavities may be taken 

 as a relative index of the calcium availability in the different sand-colloid 

 systems (94). 



loidal material in peanut soils could well explain why soils containing 

 equal amounts of exchangeable calcium do not respond in a like manner to 

 additions of calcium materials. Apparently the response of peanuts to 

 amendments of calcium is influenced greatly by the type of soil colloid 

 and the percentage calcium saturation as well as by the level of exchange- 

 able calcium. 



MINOR ELEMENTS 



Experiments conducted by several of the southeastern experiment 

 stations have failed to show any widespread response of peanuts to ad- 

 ditions of different "secondary" and "minor" elements. 



There is some evidence that certain minor-element deficiencies may oc- 



