[3] It is one of the most popular standard solution compositions for growing plants, in the scientific world at least, with more than 21,000 citations listed by Google Scholar.
[7] In Hoagland's nutrient recipes of 1938, referred to as Hoagland solution (1, 2), the number of trace elements was subsequently reduced to the generally accepted essential elements (B, Mn, Zn, Cu, Mo, Fe, and Cl).
Accordingly, the original 1933 and the modified concentrations of 1938 and 1950 for each essential element and sodium are shown below, the calculation of the latter values being derived from Tables 1 and 2:[9] Plant nutrients are usually absorbed from the soil solution.
[1][2][3] Synthesizing a sodium-free ferric EDTA complex (C10H12FeN2O8−) in a laboratory is sometimes preferred to buying ready-made products.
[6][9] Variable micronutrients (e.g., Co, Ni) and rather non-essential elements (e.g., Pb, Hg) mentioned in Hoagland's 1933 publication[1] (known as "A-Z solutions a and b"[16]) are no longer included in his later circulars.