Wadleigh a fid Richards 439 



the soil moisture supply. It is quite probable that these various soils 

 differ considerably in their fixing power for phosphate and that this 

 variation is related to the observed effects of soil moisture supply on 

 phosphate content of plants. 



The available evidence consistently shows magnesium to be relatively 

 high in plants growing under restricted soil moisture supply (u6, 82, 66). 

 This is in line with the inverse tendency for magnesium deficiency to 

 develop in plants during periods of heavy rainfall. 



Since there is a tendency for the entry of calcium and potassium into 

 plants to vary reciprocally, it could be inferred that the characteristically 

 low potassium content of plants with inadequate soil moisture supply 

 would be accompanied by a relatively high content of calcium. McMur- 

 trey et al. (82) and Thomas et al. {116) found this to be the case on 

 fertilized soils, but the latter investigators found the reverse trend on 

 their unfertilized plots. Miller and Duley (84) and Janes (66) found 

 virtually no effect of soil moisture supply on calcium content of their 

 experimental plants. It is evident, therefore, that the status of other 

 constituents in the soil have a modulating effect on calcium availability 

 under varying soil moisture content. 



As pointed out in the first part of this paper, diminishing soil mois- 

 ture content effects a concentration of the solutes in the soil solution. 

 Fertilized plants may even intensify this solute concentration as a result 

 of increased rate of moisture extraction. Thus, Jordon et a/.* found 

 that corn plants fertilized with nitrogen during a dry year not only 

 rapidly depleted the soil moisture to the wilting percentage in the sur- 

 face foot of soil, but also to the 3-foot depth. On the other hand, readily 

 available moisture continuously prevailed in the 3 feet of soil under 

 the unfertilized control plants. In a well-fertilized soil subjected to a 

 prolonged dry spell, this solute concentration may in itself inhibit water 

 availability, so that growth on the unfertilized soil may be better than 

 that on which fertilizer was applied. Neff and Potter ($7) noted that 

 newly transplanted tung trees were injured by mineral fertilization 

 during a dry year. Carolus and Woltz (27) found that during four dry 

 seasons in eastern Virginia, the more nitrogen fertilizer they added to 



*H. V. Jordan, K. D. Laird, and D. D. Ferguson. Personal communication of 

 an unpublished report. 



