ABSTRACT
The 17 elements considered essential for plant growth are carbon (C), hydrogen (H), oxygen (O), nitrogen (N), phosphorus (P), potassium (K), calcium (Ca), magnesium (Mg), sulfur (S), iron (Fe), zinc (Zn), copper (Cu), boron (B), manganese (Mn), molybdenum (Mo), chlorine (Cl), and nickel (Ni) (Fageria, 2014). Sodium (Na), silicon (Si), selenium (Se), vanadium (V), and cobalt (Co) are benecial for some plants but have not been established as essential elements for all higher plants (Mengel et al., 2001; Fageria et al., 2011). Among essential plant nutrients, C, H, O, and N are major constituents of the principal classes of compounds that make up about 95% of the fresh weight of most living plants (Epstein and Bloom, 2005). Essential plant nutrients can also be classied as metals or nonmetals. Metals include K, Ca, Mg, Fe, Zn, Mn, Cu, Ni, and Mo. Nonmetals include C, H, O, N, P, S, B, and Cl (Bennett, 1993).
