Fertilizers are used to obtain higher yields of crops. However, all nutrients are usually not available in fertilizers. Which one of the following nutrients is usually not available in fertilizers ?

Fertilizers are primarily formulated to supply macronutrients, which plants require in large quantities for growth and yield. The three primary macronutrients found in almost all commercial fertilizers are Nitrogen (N), Phosphorus (P), and Potassium (K), often referred to as the NPK ratio [5]. While plants also require micronutrients like Iron (Fe), Zinc (Zn), and Manganese (Mn) for metabolic functions, these are needed in very small concentrations [3]. Consequently, standard fertilizers typically do not include iron unless they are specifically labeled as 'multimicronutrient' or 'fortified' fertilizers [4]. Iron is usually available in the soil or provided through specialized chelated fertilizers when a deficiency is identified [4]. Therefore, among the given options, Iron is the nutrient that is usually not available in standard commercial fertilizers compared to the ubiquitous NPK components [5].

Sources

1. [2] Environment, Shankar IAS Acedemy .(ed 10th) > Chapter 5: Environmental Pollution > 3) Agricultural sources: > p. 74
2. [5] https://www.fao.org/4/a0443e/a0443e03.pdf
3. [1] Indian Economy, Nitin Singhania .(ed 2nd 2021-22) > Chapter 9: Agriculture > FERTILISERS > p. 302
4. [3] Environment, Shankar IAS Acedemy .(ed 10th) > Chapter 25: Agriculture > z. Micronutrientsl > p. 363
5. [4] Indian Economy, Vivek Singh (7th ed. 2023-24) > Chapter 9: Subsidies > 9.4 Fertilizer Subsidies > p. 287