164 THE PEANUT— THE UNPREDICTABLE LEGUME 



the crop. There is some evidence that certain varieties of peanuts may 

 respond to relatively large additions of nitrogen, despite the fact that the 

 crop is a legume. However, large quantities of nitrogenous fertilizers are 

 not commonly applied to peanuts. Unless the crops grown in rotation 

 with peanuts receive very liberal applications of potassium, it may be 

 necessary to apply some fertilizers containing this element directly to the 

 peanuts in order to obtain maximum yields and to maintain the fertility 

 of the soil. 



The importance of calcium in the nutrition of peanuts has long been 

 recognized. Generally the response of peanuts to amendments of calcium 

 has been more consistent than to additions of any other nutrient. Appar- 

 ently one of the primary functions of calcium in peanut nutrition is to 

 improve the quality of the nuts, or more specifically, to aid in the devel- 

 opment of the kernel. The better quality of nuts grown in soils well sup- 

 plied with calcium is evidenced by a lighter, firmer hull and few unfilled 

 pods (pops). 



One of the most common methods of supplying the calcium needs of 

 peanuts is to apply gypsum to the foliage at early blooming. However, 

 when the soil has been limed adequately little benefit may be derived from 

 additions of gypsum. For a number of reasons, it would appear better to 

 maintain an adequate calcium level in peanut soils through the use of a 

 liming material rather than by additions of a neutral salt such as gypsum. 

 Calcitic lime should be superior to one high in magnesium. 



Some investigators have obtained a fair correlation between the ex- 

 changeable calcium levels in soils and the response of peanuts to amend- 

 ments of lime or gypsum, and expected responses have been predicted on 

 such a basis. However, for a more exact estimate of the need for calcium 

 in peanut soils, the nature of the soil colloids and the percentage base 

 saturation, as well as the exchangeable calcium level, need to be con- 

 sidered. 



There is little evidence that any of the so-called "secondary" and 

 "minor" elements are normally limiting the yield of peanuts, except per- 

 haps on heavily limed soils where deficiencies of manganese may occur. 



A review of peanut-fertilization research suggests that too little atten- 

 tion has been given to the method of placement of peanut fertilizers. 

 Studies have shown that in order for calcium to be most effective it 

 should be localized in the zone in which the pods develop. On the other 

 hand, a high concentration of potassium in the fruiting zone may be 

 harmful because of its effect on fruit quality, especially at low-calcium 

 levels. Furthermore, fertilizer materials, if placed too close to the seed at 



