Manganese (Mn)

Marijuana Horticulture

by Jorge Cervantes

Manganese deficiency is relatively common indoors.

Manganese is engaged in the oxidation-reduction process associated with the photosynthetic electron transport. This element activates many enzymes and plays a fundamental part in the chloroplast membrane system. manganese assists nitrogen utilization along with iron in chlorophyll production.

Young leaves show symptoms first. They become yellow between veins (interveinal chlorosis), and the veins remain green. Symptoms spread from younger to older leaves as the deficiency progresses. Necrotic (dead) spots develop on severely affected leaves which become pale and fall off; overall plant growth is stunted, and maturation may be prolonged. Severe deficiency looks like a severe lack of magnesium.

To treat the deficiency, lower the pH, leach the soil, and add a complete, chelated micronutrient formula.

Young and newer growth develop chlorotic, dark orange to dark, rusty brown mottling on the leaves. Tissue damage shows on young leaves before progressing to the older leaves. Growth is slower, and overall vigor is lost. Toxicity is compounded by low humidity. The additional transpiration causes more manganese to be drawn into the foliage. A low pH can cause toxic intake of manganese. An excess of manganese causes a deficiency of iron and zinc.