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A Review of the Use of the Basic Cation Saturation Ratio and the "Ideal" Soil

School of Land and Food Sciences, The Univ. of Queensland, St. Lucia, Qld, Australia 4072

View larger version (18K): [in this window] [in a new window]   Fig. 1. Effect of initial soil pH on the nodulation of soybean. Calcium was supplied at three levels: 0.05, 0.10, or 0.20 mmolc Ca per plant. Data taken from Albrecht (1937).

View larger version (18K): [in this window] [in a new window]   Fig. 2. Nitrogen fixation (measured as the difference between final plant N content and initial seed N content) as related to the efficiency of Ca use (the percentage of the Ca supplied that was taken up by the plants) at different degrees of Ca saturation of a clay mineral. Data from Albrecht (1939). Vertical dotted line is 65% Ca saturation. Scales on each of the axes presented as in Albrecht (1939).

View larger version (18K): [in this window] [in a new window]   Fig. 3. The effect of the saturation of the soil cation exchange capacity by various amounts of Ca, Mg, and K on the relative yield of ladino clover. Data taken from Giddens and Toth (1951) for two (Tifton and Annandale sandy loams) of the four soils investigated. Data are sorted in order of decreasing Ca saturation. The columns at the far right of the graph (65:10:5) would reflect the "ideal soil" as proposed by Bear et al. (1945). Giddens and Toth (1951) did not present statistical differences.

View larger version (14K): [in this window] [in a new window]   Fig. 4. Effect of the exchangeable Ca/Mg ratio (2.2:1–14:1) on the relative dry matter yield of German millet in two soils. Data taken from McLean and Carbonell (1972). The dotted line indicates the "ideal" Ca/Mg ratio of 6.5:1 as stated by Bear et al. (1945).

View larger version (15K): [in this window] [in a new window]   Fig. 5. Effect of the exchangeable Ca/Mg ratio (0.25:1–31:1) on the relative shoot dry weight of alfalfa at two P fertilization levels. Soils were prepared by mixing homoionic clays at various ratios, with K-saturated clays accounting for 10% of the total. Data taken from Hunter (1949). The dotted line indicates the "ideal" Ca/Mg ratio of 6.5:1 as stated by Bear et al. (1945).

View larger version (11K): [in this window] [in a new window]   Fig. 6. Effect of the exchangeable Ca/K ratio (1:1–91:1) on the relative dry weight of alfalfa. Soils were prepared by mixing homoionic clays at various ratios. Data taken from Hunter et al. (1943). The dotted line indicates the "ideal" Ca/K ratio of 13:1 as stated by Bear et al. (1945).

View larger version (12K): [in this window] [in a new window]   Fig. 7. Effects of the Ca/Mg ratio, sodium adsorption ratio (SAR), and salinity (presented as the total cation concentration [TCC, mmolc/L]) on the relative hydraulic conductivity of a surface soil of a sodic red-brown earth (Rhodoxeralf). The relative hydraulic conductivity has been calculated separately for each TCC series. Data taken from Rengasamy et al. (1986).