Iron in Soils

Low iron content in soil can cause leaves to turn yellow.

Soil provides a plant with many of its necessary nutrients, including iron. As a plant grows it takes iron and other nutrients from the soil to help it stay healthy. The nutrients available in soil can be affected by the soil's components and texture. When plants receive too little iron from the soil, the plants may suffer from a condition known as iron chlorosis.

Plant Nutrients

A plant requires the presence of 13 different nutrients from the soil in which it is planted. The nutrients may be divided into two main categories including macronutrients and micronutrients. According to the North Carolina Department of Agriculture and Consumer Services (NCDGR) website, macronutrients are defined as those plants use most quickly from the soil. They include nitrogen, phosphorus, potassium, calcium, magnesium and sulfur. Micronutrients are elements that are essential for plant growth, but that plants only use in small quantities. The micronutrient category includes iron, boron, copper, chloride, manganese, molybdenum and zinc.

Soil Components

Soil around the world is made up of the same basic components, according to the Encyclopedia of Earth. In addition to mineral components, soil contains air, water, dead organic matter, and living organisms including plants and bugs. While soils around the world contain the same elements, the combinations vary producing different types of soils. The three main types of soil textures include sandy, silt and clay soils.

Iron Chlorosis

Iron chlorosis is defined as an iron deficiency in the soil, according to the Utah State University website. Plants affected by a lack of iron suffer from a lack of chlorophyll. Chlorophyll is the element in plants that helps aid the process of photosynthesis. Photosynthesis is the process by which a plant uses the sun's energy to produce sugar to feed the plant. The effects of iron chlorosis are far-reaching and can be severely damaging for a plant.

Symptoms

Depending on the severity of the iron deficiency, the symptoms of iron chlorosis range from mild to severe. Interveinial chlorosis is the most common symptom of this nutrient deficiency and causes leaves to turn yellow while the veins turn dark green. Leaves may also turn white if an iron chlorosis infection is severe, according to the Utah State University website. Leaves will turn brown with leaf scorch on the outer edges of the leaf as the leaf cells die. Where the soil is severely lacking in iron, limbs of trees may die. When the problem is left untreated for several years, the entire plant may die.

Causes

According to the Utah State University website, the causes of iron chlorosis are complex and not completely clear. This problem develops most commonly in alkaline soils that contain lime. Alkaline soils are soils with a pH reading greater than 7. Cool soil temperatures and restricted air movements also contribute to an iron deficiency. Plastic sheets, compacted soils, water saturation and the removal of topsoil contribute to poor soil conditions and the development of iron chlorosis. Planting native plants, which are adapted to soil in a particular area may help plants avoid the complications associated with iron chlorosis. Adding organic compounds such as grass clippings and compost may help increase the mineral content in soil.

References

• Utah State University: What is Iron Chlorosis and What Causes It?
• Encyclopedia of Earth: Soil
• North Carolina Department of Agriculture and Consumer Services: Plant Nutrients