138 THE PEANUT— THE UNPREDICTABLE LEGUME 



Numerous tests conducted in Virginia have emphasized the need for 

 calcium in the production of large-seeded varieties of peanuts. Batten 

 (29) has suggested that an adequate calcium level may be maintained by 

 applying 1,500 to 1,800 pounds of ground limestone per acre or its equiva- 

 lent to peanut soils every 3 or 4 years. Large applications at one time 

 have been found to be harmful. It was suggested that the pH be main- 

 tained between 5.8 and 6.2, and on the lighter soils the pH should never 

 exceed 6.4. Batten reports that gypsum is almost universally used where 

 the large-seeded peanuts are grown. However, this material has not been 

 found to increase yields where lime has been used to maintain a "suit- 

 able" soil reaction. 



The results of other experiments at different localities in the United 

 States are varied. The response or lack of response may be explained 

 in most cases by the mineralogical nature of the soil and the level of 

 calcium. Generally, however, the soils on which peanuts are grown are 

 relatively low in calcium and unless large amoijnts of lime have been 

 applied in recent years some benefit may be expected from the use of this 

 element. 



Sources of Calcium 



There is considerable evidence that peanuts will make satisfactory 

 growth on relatively acid soils provided the calcium needs of the plant 

 are satisfied. Thus, the primary consideration in the use of lime or other 

 calcium-bearing materials for peanuts is to furnish an adequate supply 

 of the nutrient calcium. The three calcium-bearing materials most com- 

 monly used for peanuts are gypsum or landplaster (CaS04.2H20), cal- 

 citic limestone and dolomitic limestone. Numerous tests have been made 

 to determine the most satisfactory of these materials for peanuts. 



Little differences in peanut yields were observed at two locations in 

 Mississippi (14) from the use of 400 pounds of gypsum under the seed, 

 400 pounds of gypsum dusted on the plants, and 400 pounds of dolomite. 

 However, little response was obtained from any of these treatments. In 

 other experiments 1,200 pounds of lime yielded somewhat better than 

 400 pounds of gypsum. 



Comparable yields of large-seeded peanuts were obtained in experi- 

 ments in Virginia (30) with 500 pounds of gypsum, 2,000 pounds of 

 burnt shells, and 4,000 pounds of ground shells. Other studies (32) in- 

 dicated that ground oyster shells and dolomitic limestone were of equal 

 value for peanuts. 



Rogers (95) studied the effect of ten sources of calcium upon the yield 



