Seventeen elements are considered to have met the criteria for designation as plant nutrients. Carbon, hydrogen, and oxygen are derived from air or water. The other 14 are obtained from soil or nutrient solutions. It is difficult to assign a precise date or a specific researcher to the discovery of the essentialiality of an element. For all the nutrients, their roles in agriculture were the subjects of careful investigations long before the elements were accepted as nutrients.
Many individuals contributed to the discovery of the essentlity of elements in plant nutrition. Much of the early research focused on the beneficial effects or sometimes on the toxic effects of the elements.
Generally, an element was accepted as a plant nutrient after the body of evidence suggested that the element was essential for plant growth and reproduction, leading to the assignment of certain times and individuals to the discovery of its essentiality.
Beneficial elements may stimulate growth or may be required by only certain plants. Silicon, cobalt, and sodium are notable beneficial elements. Selenium, aluminium, vanadium, and other elements have been suggested to enhance growth of plants.
Some of the beneficial elements may be classified in the future as essential elements as developments in chemical analysis and methods of minimising contamination during growth show that plants will not complete their life cycles if the concentrations of elements in plant tissues are diminished sufficiently.
Nickel is an example of an element that was classified as beneficial but recently has been shown to be essential.
Element | Date of Essentiality | Researcher |
Nitrogen | 1804 | de Saussureb |
1851–1855 | Boussingaultb | |
Phosphorus | 1839 | Liebigc |
1861 | Ville | |
Potassium | 1866 | Birner & Lucanusb |
Calcium | 1862 | Stohmannb |
Magnesium | 1875 | Boehm |
Sulphur | 1866 | Birner & Lucanusb |
Iron | 1843 | Grisc |
Manganese | 1922 | McHarguec |
Copper | 1925 | McHarguec |
Boron | 1926 | Sommer & Lipmanc |
Zinc | 1926 | Sommer & Lipmanc |
Molybdenum | 1939 | Arnon & Stoutc |
Chlorine | 1954 | Broyer, Carlton, Johnson, & Stoutc |
Nickel | 1987 | Brown, Welch, & Cary |