Soil Liming Investigations: I. The Calcium Carbonate Equilibration Method of Liming Soils for Fertility Investigations 1

W liming materials are applied to soils in large amounts, marked changes are induced in the physical, chemical, and biological properties of soils. The influence of lime on many of these properties has been reported in the literature, but there is some disagreement in the results. Furthermore, there are considerable apparently conflicting results on the effect of lime on soil productivity or plant growth (6, xI, ~2)3. There is not complete agreement on the lime requirement of soils either from the standpoint of laboratory or field methods. The methods for the former have been more or less empirical (4, 5, ~o), while for the latter the general procedure has been by trial and error. Thus, there is a real need for a more suitable liming method in order to investigate the effects and feasibility of liming soils as well as to study the lack of agreement in previous investigations. A liming method by which increments of lime are added to the soil instead of a single amount as previously proposed(4, 5, ~o) would advantageous in that a yield curve could be obtained. A soil constant or an equilibrium point would be necessary for such a liming method in order that comparable results could be obtained on widely different soils. The saturation point of soils defined by BradaCield and Allison (2) seems admirably suited for a base point for the liming method. A saturated soil is defined by them as one at equilibrium with an excess of solid CaCO~ and the CO~ partial pressure of the atmosphere at 25° C. In many respects this point is perhaps the nearest approach to a soil constant yet studied. The addition of increments of lime to the point of saturation and beyond this point will result in the complete range of pH values and degrees of base saturation from that of the unlimed soil to completely saturated soils. Both soil reaction and base saturation are generally considered to influence soil fertility. The proposed liming method includes not only the maximum amount of lime which will react with the soil, but also increments below and above this amount if desired. It appears that the method proposed would be applicable to the study of widely different soils, especially since liming iniury may or may not occur on all soils. Liming soils in greenhouse cultures or on field plats by this method should give results from which the optimum amount of lime for certain crops or cropping systems could be obtained. A search Of the literature revealed no systematic study of