Is it common for marijuana plants?
Manganese (Mn) deficiency is rare when growing marijuana and almost always associated with Fe-zinc deficiencies.
Generally, this deficiency is found in the young cannabis leaves. The tissue of the leaf turns yellow and you find small necrotic areas (small areas of tan/brown dead tissue) in the middle of the leaf. Most of the time the veins stay green. Along the margins the cannabis leaf becomes outlined in a ring of dark green. Iron deficiency occur when the soil contains too much of Mn. Add to this, that the marijuana plant shows lack of vigor.
It is immobile.
Role in nutrition of the plant
Manganese aids the breakdown of enzymes for photosynthesis production and chlorophyll production. It also helps making the nitrates available for protein production.
Solving the problem
Use foliar feed with a water-soluble fertilizer high in Mn (like Fe-Zn-Mn fertilizer, hydro micros or Mn chelate), for fast relief. Add the fertilizers to the nutrient/water mix. Greensand and compost can aslo be used (they contain Mn) but water-solubles are faster absorbed by marijuana plants than compost and greensand.