The role of nutrients

Soils may be naturally low in nutrients, or they may become deficient due to nutrient removal by crops over the years without replenishment - or when high-yielding varieties are grown that have higher nutrient requirements than do local varieties.

The two main types of nutrients. All of the essential nutrients are important but in varying quantities

• Macronutrients are needed by plants in large quantities. The "primary nutrients" are nitrogen, phosphorus, and potassium. Today, sulphur is also considered a key macronutrient. Macronutrients include both primary and secondary nutrients.
• Micronutrients (or "trace elements") are required in very small amounts for correct plant growth. They need to be added in small quantities when they are not provided by the soil.

Every plant nutrient, whether required in large or small amounts, has a specific role in plant growth and food production. One nutrient cannot be substituted for another.