SOIL FERTILITY 



133 



Potassium 



It is well recognized that peanuts are especially heavy "feeders" of 

 potassium. Yet, despite the relatively large amount of potassium absorbed 

 by peanuts (see table 1) the yield responses to applications of potash 

 fertilizers are often very small or negligible, even on soils of low K con- 

 tent. In fact, peanuts appear to be quite unique in their ability to absorb, 

 potassium and make satisfactory growth on soils so deficient in available 

 potassium that many other crops would fail to grow. 



An average of the yields obtained in an experiment conducted at the 

 Georgia Coastal Plain Experiment Station (13) over a 10-year period 

 shows that the use of 32 pounds of potash in combination with nitrogen 

 and phosphorus increased the yield of Spanish peanuts only 139 pounds 

 per acre. In experiments conducted by the North Carolina Station (46) 

 between 1938 and 1943, 12 to 48 pounds of K^O per acre proved bene- 

 ficial in only one of the locations. In several instances the yields were 

 actually reduced by the application of potash. The exchangeable potassium 

 level of these soils was 75 pounds or greater at each location. 



CORRECTED YIELD 

 IN POUNDS 

 PER ACRE 



NO 

 CALCIUM 



WITH 

 CALCIUM 



TRUE SHELLING 

 PER CENT 



O = NO TREATMENT 

 K = 48 LBS. 



KgO 



K 



NO 

 CALCIUM 



WITH 

 CALCIUM 



Courtesy North Carolina Agricultural Experiment Station (47) 



Figure 1. — The response of peanuts to potash, with and without addi- 

 tions of calcium. Soil = Kalmia sandy loam ; pH = S.3 ; exchange 

 capacity = 3.13 m.e./lOO grams ; exchangeable Ca, Mg, and K = 

 O.SO, 0.27 and 0.12 m.e./lOO grams respectively. Calcium equiva- 

 lent to 130 pounds CaO was applied as CaS04.2H20 on the 

 foliage in July. 



