How the Presence of Iron Affects Bean Plant Growth

What Iron Does

• Iron is a micronutrient. If you were to take an entire bean plant, roots and all, dry it completely, and measure out the individual nutrients, iron would be less than 100 parts per million. Iron may be in minor quantities in your bean, but it plays a major role in chlorophyll production. Chlorophyll, in turn, plays a key role in producing energy, resulting in better growth. Chlorophyll is also responsible for the dark green color of the leaves, shoots and beans. When a plant is deficient in iron, the leaves appear yellow.

Presence of Iron in Acid Soils

• Acid soils have a low pH, typically on the pH scale from 1 to 6. If you take a look at the relationship between soil pH and relative availability of plant nutrients, you will find that iron is readily available in soils with a pH lower than 6. This means that the iron is soluble in water, and in a form that can be used by beans for uptake. Beans grown in acid soils tend to not have problems with chlorotic leaves due to iron deficiency. The largest bean growers can be found in the east and northwest states due to their acid rich soils.

Presence of Iron in High pH Soils

• Dry, desert regions often have alkaline, or high pH soils. Most soils have plenty of iron, but iron becomes unavailable for plant growth in pHs over 7. Iron solidifies when coupled with oxygen, hydrogen and carbonates. Alkaline soils have a concentration of carbonates due to their lime (calcium carbonate) content. Beans grown in alkaline soils can exhibit the typical symptoms of iron chlorosis, even though the iron may be present in the soil. You can correct this problem using a chelated iron.

Correcting Iron Deficiency

• Chelated iron can be found in several different forms, including: foliar spray, powder, granules and tablets. Chelated iron is best used in soils with a high pH due to its ability to keep the iron in an available form. Chelation comes from the Greek word chele, or claw. The iron cation is held between two atoms to protect it from solidifying. Beans benefit greatly from a foliar application to quickly correct the problem.