114 THE PEANUT— THE UNPREDICTABLE LEGUME 



vegetative character, flower and fruit production, and the mineral compo- 

 sition of the plants. This balance relates not only to the nutrient supply 

 in the root area, but also in the fruiting area. Plants are vegetative and 

 produce few fruit when calcium is not applied to the fruiting area (10, 

 37). Thus, the nature of the entire plant may be altered by the lack of 

 calcium in the fruit zone. This does not mean that fruit absorption of 

 nutrients is as important as root absorption, but the special requirements 

 of the fruiting organs cannot be disregarded in the evaluation of fertilizer 

 requirements. 



A number of workers (14, 15, 19, 20, 70) have emphasized the effect 

 of the calcium-potassium relationship on fruit production. Others (83) 

 have indicated that the potassium-magnesium ratio is important in this 

 respect and that the relation of the calcium, potassium and magnesium 

 supply was indicative of the relative yield of marketable nuts. The im- 

 portance of a balanced ration for plants is obvious. However, it is impos- 

 sible to strive for a balanced nutrient program for the peanut until factors 

 responsible for yields are identified. 



NUTRITION AS RELATED TO DISEASE 



The relation of the nutritional status of the peanut plant to its disease 

 susceptibility is probably more important than generally realized. The 

 prevalence of leaf-spot infection was far greater on plants grown on a 

 magnesium-deficient solution than of plants grown on a deficiency of 

 other elements ( 12) . Applications of gypsum have also been reported ( 19) 

 to cause the foliage of peanut to be very susceptible to leaf spot, resulting 

 in early defoliation. 



Concealed damage of the peanut seed is any internal breakdown of the 

 cotyledons which is not evident upon external examination. Wilson (92) 

 indicates that one type of concealed damage appears to be physiological 

 in nature, but its occurrence was unimportant in Alabama. Internal 

 breakdown of the seed might be related to nutrition but experimental 

 evidence of such is lacking. 



Sulfur dust is commonly applied to the foliage of peanuts to control 

 leaf spot and certain insects. The sulfur may also act as a nutrient in 

 some instances, especially where the supply of sulfur in the soil is low 

 (8, 38). Some results^ suggest that when sulfur was applied to the soil 

 the foliage of the peanut plant was less susceptible to the leaf-spot in- 

 fection. 



5 Unpublished results, Florida Agricultural Experiment Station. 



