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1 <br /> <br /> 4.4 Soil Sampling Analysis and Discussion: 1986, 1988, and 1993 Studies <br />' <br /> Soil sampling of the topsoil material with which the Test Plots were constructed was <br /> undertaken in 1983 prior to placement (Champion, 1983). Two samples of the material <br />' to be used were taken from 0-30" and 30-48" depths from one soil pit. Analysis of the <br /> 1983 samples showed pH values averaging 7.97, EC values averaging 0.54 mmhos/cm, <br /> and SAR values averaging 1.73 meq/1. In 1986 and 1988, samples were taken and <br />analyzed from the Test Plots and other locations on the RDA (Champion, 1986, <br /> WRDC, 1989). Table 38 presents the soil chemical analytical data over time. Figures <br /> 36 and 37 graphically illustrate soil chemical parameters over time and soil depth. As <br />' noted for the 1993 data, soil pH values remained relatively constant over depth and <br /> time (Figure 33, Table 38). The other soil parameters showed more variability, and <br />' several had distinct trends. Electrical conductivity (EC) values, calcium, magnesium, <br /> and sodium concentrations, as well as sodium adsorption ratios decreased over time in <br /> the 0-6" and 6-12" soil depths. That these decreases occurred indicates that cations are <br />' not migrating to these shallow soil depths from lower ]evels as was previously <br /> postulated. Samples from the 12-18", 18-24" and 24-48" depths showed increases in <br /> the soil parameters measured. EC and SAR values from the 18-24" and 24-48" depths <br />' showed the largest increases in measured EC, Ca, Mg, Na, and SAR values, indicating <br /> ionic movement within these depths over time. Interestingly, these elevated levels of <br />' cations do not appear to be migrating to levels above 12-18". As was noted earlier, <br />this may be a result of dry conditions of the soil column at the shallower depths, <br /> preventing upward migration of salts, whereas sufficient moisture at the deeper levels <br /> has allowed cation migration. Since decreases in cation concentrations over time were <br />' noted in the 0-12" depth range, some downward leaching of cations must be occumng. <br /> Uptake of cations by plant roots may also be occurring, however, leaf chemistry <br />' analyses (WRDC, 1989) did not detect elevated levels of macronutrients, <br /> micronutrients, or trace metals in the plants sampled. <br /> <br /> <br />' 75 <br />