ABSTRACT
Seventeen elements are considered essential plant nutrients since they are involved in metabolic functions such that the plant cannot complete its life cycle without these elements (Table 1). The most abundant nonmineral nutrients (C, H, and O) are obtained from CO2 and H2O and converted into carbohydrates that form amino acids, proteins, nucleic acids, and other compounds through photosynthesis. The supply of CO2 has increased from ~310 to 390 ppm CO2 since 1960. The supply of H2O rarely limits photosynthesis directly but reduces plant growth when plant-available H2O is limited. The remaining 14 macronutrients and micronutrients are classifi ed on their relative abundance in
So il-
So il
plants. The N concentration in most plants is greater than the other 13 nutrients combined. Although nutrient content varies greatly between plant species, most plants also require substantial amounts of Ca and K (Table 1). Plants absorb many nonessential elements present in the soil solution. For example, Al3+ in plants can be high when soils contain relatively large amounts of soluble Al (low pH soil). In some severely acid soils, Al toxicity can reduce plant growth and yield. In high-pH soils, Na+ can be elevated in soil solution and/or on the exchange complex, increasing Na+ in the plant, which can also be detrimental to plant growth.
