INFLUENCE OF FORM, SOIL-ZONE, AND FINENESS OF LIME AND MAGNESIA INCORPORATIONS UPON OUTGO OF CALCIUM AND MAGNESIUM

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Abstract
A 4-year lysimeter study of surface-and subsurface-zone incorporations of Ca(OH)2 and 4 separates and a composite of limestone and of dolomite at a constant rate of 2000 pounds of CaO per 2,000,000 pounds of soil. The maximum increase in Ca outgo from surface-zone incorporations during 4 years was only 6.8% of the addition; and although some influence of form and fineness was recorded, the untreated subsurface zone tended to produce a uniform outgo. In the absence of the retardative effect of a layer of untreated soil, the lower zone incorporations gave a maximum increased outgo of 33% of the addition. Although the hydrated lime gave the greatest outgo during the 1st year[long dash]about 60% of its total[long dash]its final increase was almost identical with the increases from the 2 finer limestone separates. Losses from the high-calcic additions during the 1st year were uniformly maximum with decided decreases for the next 3 years for both zones. The differences due to fineness, zone and time were not so great for the dolomite additions, but they showed positive effects from the imposed conditions. There was a very little difference between the magnesia outgo from the controls and the losses from either limestone or dolomite additions to the surface zone. Losses from subsurface-zone incorporations were consistently greater than from surface-zone incorporations. Both zones generally gave the maximum annual outgo during the 1st year. The influence of fineness of dolomite separates was especially marked in the subsurface outgo for both annual and 4-year periods. In the completely disintegrated finer limestone separates in the subsurface zone there was no increased Mg outgo from the decomposition of the Mg content of the limestone. Repressed Mg solubility was indicated by the high-calcic additions to the lower zone. The total Ca-Mg leachings from the surface-zone incorporations were small, comparable for limestone and dolomite, and related to the degree of fineness. The total Ca-Mg leachings from the subsurface-zone incorporations were uniformly greater than those from the surface-zone incorporations. Limestone separates gave totals uniformly higher than those from the corresponding dolomite separates, the disparity decreasing with increasing fineness. The total outgoes from Ca(OH)2 and from 100-mesh limestone and dolomite were almost identical.

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