Basic cation saturation ratio

Albrecht campaigned against the concept of an acid soil causing poorer crop growth rather, it is the calcium deficiency that needs to be remedied. The acid soil solution dissolves rock particles, such as rock phosphate and limestone, to release beneficial nutrients such as phosphate and calcium respectively. It also mobilizes the other adsorbed ions off the clay-humus colloid. He estimated the optimum ratios of calcium to magnesium and calcium to potassium. These were approximately from 4 1 to 7.5 1, and from 15 1 to 38 1 respectively. The higher the Ca K ratio, the more proteinaceous 

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Eckert, D.J. (1987) Soil test interpretations Basic cation saturation ratios and sufficiency levels. In Brown, J.R. (ed.) Soil Testing Sampling, Correlation,... 

Eckert, D.J. and McLean, E.O. (1981) Basic cation saturation ratios as a basis for fertilizing and liming agronomic crops I. Growth chamber studies. Agronomy Journal 73, 795-799. 

McLean, F.O. (1977) Contrasting concepts in soil test interpretation sufficiency levels of available nutrients versus basic cation saturation ratios. Soil testing correlating and interpreting the analytical results. A5A Special Publication No. 29, 39-54, American Society of Agronomy, Madison, Wisconsin. 

Discussion. The colloidal clay and humus soil fractions are negatively charged and therefore attract and adsorb positive ions (cations) on to exchange sites. These may be the so-called basic cations defined above, or the acidic cations H+ and Al +. These cations are not soluble in water when in the adsorbed state, but can exchange with H+ which is present in the acidic vicinity of the plant root system. They are now in solution and able to be absorbed into the plant. The extent to which the exchange sites are saturated with cations, together with the ratios of the cations to each other, indicates the nutrient supplying power of the soil. 

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