It was realised by researchers into plant metabolism that plants took in their nutrients as simple inorganic ions, and that soil, while a source for such nutrients, was not essential. While a plant's nutrients come from the soil, the only nutrients a plant can successfully absorb are those that dissolve into the plant's water supply. By introducing the required nutrients into a plant's water supply artificially, soil is no longer required for the plant to thrive. The first example such researcher was a John Woodward of England, who, in 1699, grew plants in water to which he had added various soils, demonstrating that earth contained various substances which the plants needed besides water.
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