Soil fertility and plant nutrition

Soil fertility refers to the ability of soil to provide essential nutrients for plant growth.
Fertile soil tends to be rich in minerals, has a good balance of soil air and water, and contains plenty of organic matter.
Macronutrients - nitrogen, phosphorus, and potassium - are needed in large quantities by plants while micronutrients, such as iron, zinc, and boron, are important but required in much smaller amounts.
The ability of soil to hold and release nutrients is known as cation exchange capacity (CEC). Soils with a high CEC can hold more nutrients and therefore tend to be more fertile.

For optimal growth, plants require both macronutrients and micronutrients from the soil.
Nitrogen is a key element in proteins and chlorophyll. It helps plants with rapid growth, leaf development, and colour.
Phosphorus is essential for energy transfer and storage in plants. It’s also vital for cell division and development of new tissue.
Potassium regulates plant metabolism and affects water pressure regulation inside cells, disease resistance, and quality of seeds and fruit.
Micronutrients are needed in much smaller quantities. They include elements such as iron, manganese, zinc, copper, molybdenum, and boron. Despite their minute requirement amounts, they play key roles in plant growth and development.

Soil fertility can be improved by adding organic matter, using fertilisers, implementing crop rotation, and maintaining a favourable soil pH.
Organic matter, like compost and manure, improves soil structure, water-holding capacity, and nutrient content.
Fertilisers can provide essential nutrients to the soil. However, excessive use can lead to nutrient imbalance and environmental issues.
Crop rotation helps maintain soil fertility by preventing the depletion of certain nutrients. Certain crops, like legumes, can also fix nitrogen from the air, adding it to the soil.
Maintaining a neutral or near-neutral soil pH (around 6 to 7) ensures that most nutrients remain available for plant uptake.

Plants take up nutrients from the soil through their roots. The majority of this uptake occurs in the topsoil, where concentration of nutrients is often highest.
The exchange of nutrients occurs at the the root-soil interface, in a region known as the rhizosphere. Plant roots release chemicals to attract beneficial soil microorganisms, which help in nutrient uptake.
The health and fertility of the soil directly impacts the health and productivity of the plants growing in it. Therefore, maintaining soil fertility is a key aspect of horticulture.