Compositions of Soils and Plants

Element Soil Content (Weight%) Plant Ash Content/Soil Content Annual Plant Uptake (kg ha-1 yr-1) Soil Content/ Annual Plant Uptake (yrs) 

From Vinogradov s data in N. F.Ermolenko. 1972. Trace Elements and Colloids in Soils. Israel Program for Scientific Translations, Jerusalem. 

Column 2 of Table 1.1 shows the ratio of plant content to soil content of important ions. The hydrogen, carbon, and oxygen ratios are omitted because these ions are not derived directly from soils. The ratios are crude indices of the relative availability of soil components to plants. Calcium, sulfur, nitrogen, and potassium in soils are more available than iron and manganese. One goal of soil chemistry is to explain why ions in soils vary widely in their degree of plant availability. 

Column 3 shows the approximate annual plant uptake per hectare (ha) of the elements, assuming an annual dry matter production of 10 000 kg ha-1. The amounts of calcium, potassium, and nitrogen absorbed greatly exceed plant absorption of the other elements. 

The data in Table 1.1 are illustrative rather than quantitative. Soil has supplied the essential elements to living organisms since terrestrial life began. The Exhaustion Plot at Rothamsted Experiment Station in England, for example, has operated continuously since 1845 and has shown that the worst agricultural practice—removing all plant material at harvest from the soil each year and no fertilization to make up the losses—reduces but does not stop plant growth or crop yields. 

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Six non-physico-chanical properties have been used to predict cation toxicity (Table 5.21). These include serum concentrations, calmodulin activity, freshwater concentrations, abundance in the earth s crust, soil concentrations, and elemental composition of soils and plants. 

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