SOIL FERTILITY 



141 



sible to predict the most effective means of supplying calcium to this 

 crop. 



On most soils it would appear to be better to meet the calcium needs 

 of peanuts by liming materials rather than through the use of neutral cal- 

 cium salts such as gypsum. With the possible exception of tobacco, most 

 of the crops which might be grown in rotation with peanuts would benefit 

 from the use of lime on the more acid soils. Furthermore, on very acid 

 soils (below pH 5.0) peanuts themselves may respond more to liming 

 materials than to additions of neutral calcium salts. For example, the 



Courtesy North Carolina Agricultural Experiment Station (81) 



Figure 4. — The response of Virginia Bunch peanuts to additions of one ton of 

 dolomitic limestone. The stunted, light colored plants, were growing on soil 

 at a pH of 4.7 and with 0.46 m.e. of exchangeable calcium. 



response to lime may be evidenced by a darker, greener vegetation and an 

 increase in plant size as shown in figure 4. The stunted, light-colored 

 condition of peanuts on very acid soils is due in part to a deficiency of 

 nitrogen, resulting from a reduction in activity of nitrogen-fixing micro- 

 organisms. Mann (69) has reported that the addition of lime to virgin 

 Norfolk and Coxville soils (pH 5.3 and 4.5) resulted in a large increase 

 in nodulation of peanuts while gypsum reduced the nodulation. In view of 

 recent work (53, 77, 97, 113) with other legumes, the poor growth of 

 peanuts on very acid soil may be due in part to a toxicity of such elements 

 as manganese, iron and aluminum. Too, there is evidence (28, 39, 78) 



