Does Iron Affect the Growth of Bean Plants?

Iron -- What It Does

• When it comes to nutrition for plants, there are macronutrients and micronutrients. Macronutrients are nutrients that are found in at least 0.1% of the dry matter. These nutrients include nitrogen, potassium, phosphorus, sulfur, calcium and magnesium. Micronutrients are those nutrients that are found in a very small percentage of the dry matter -- less than 100 parts per million. These micronutrients include chlorine, manganese, boron, zinc, copper, molybdenum and iron. Just because iron is found in small portions in the plants does not make it any less important. Iron is responsible for the production of chlorophyll. Chlorophyll is used in photosynthesis to help produce energy for the plant to grow. Without iron, plants can have significant reduction in growth.

Symptoms of Iron Chlorosis in Beans

• To determine if your beans are suffering from an iron deficiency, there are a few key symptoms to look out for. The new leaves on beans will unfold with a light yellow color, almost white. The plant will also have a stunted or slower growth rate than beans not deficient in iron. Gently pull out the worst-looking plant to inspect the roots. If the roots are brown and give off an odor, you can confirm that the yellowing is being caused by a lack of iron. Healthy bean roots are white and will not smell.

Causes of Iron Chlorosis

• Many soils have plenty of iron in them, but it is not in a form that plants can use. Iron must be in a water-soluble form in order for a plant to uptake it through the roots. Iron will form a solid (or precipitate) when combined with oxygen, hydrogen and carbonates. High pH soils are high in calcium carbonate (lime) due to the lack of precipitation to leach out the lime. It is common in high pH soils to see iron deficiency.

Affects on Bean Growth

• Due to the fact that iron is indirectly related to energy production in a plant, it is safe to say that there will be several effects on beans with iron chlorosis. These affects include slower growth rate, reduction in flowers and beans and smaller leaves. Beans germinate, grow and produce quickly. Frequent inspections should be made to keep an eye out for the first signs of iron deficiency, especially in high pH soils of the arid mountain west.