THE LIME-MAGNESIA RATIO 123 



not to a deficiency of iron, as claimed by other investigators 

 above cited, and that magnesium carbonate when apphed to the 

 roots, in solution, gives good results. 



CRITICAL REMARKS ON THE INVESTIGATIONS ABOVE REVIEWED 



In a critical examination of the foregoing data which are in 

 support of Loew's lime-magnesia ratio hypothesis, one can not 

 help being impressed with the oversight, or at least lack of at- 

 tention to several important factors which enter into a con- 

 sideration of the validity of the hypothesis in question. The 

 lack of extensive field experiments, the very short period al- 

 lowed in the different experiments for testing the hypothesis, 

 the addition of calcium and magnesium salts in various forms 

 to media, whether they be soils, sands, or solutions of widely 

 different character and composition, as well as an utter disregard 

 of the general principle of antagonism between salts, or antago- 

 nism between ions, which is coming to be more and more firmly 

 established every year, would all seem to call in question the 

 desirability of the acceptance of the results discussed as adequate 

 in themselves at least, for the establishment of Loew's hypothesis. 



We may now proceed to a more extended examination of the 

 investigations which are above reviewed. In examining the 

 data submitted in favor of the lime-magnesia ratio or those above 

 referred to as the positive investigations, we find that the chief 

 aim has been to overcome an excess of either lime or magnesia 

 in a soil by the addition of the other, regardless of whether the 

 lime or magnesia was added in an artificially prepared soil, or 

 was present to begin with in a natural soil. After such addi- 

 tions have been made and the crops grown, then, depending upon 

 the effects which additions of materials like those named pro- 

 duced on the crop, certain deductions were drawn as to the suit- 

 ability of one or another ratio for the particular crop under in- 

 vestigation. The criterion, then, for the estabhshment of the 

 principle of the lime-magnesia ratio hypothesis as well as for the 

 establishment of the proper ratio with the principle for a given 

 crop, is merely the kind of growth obtained by a certain chemi- 



y\ 



