Iron(Fe) is an immobile element. Its deficiency usually shows up at a time of rapid growth for your plants and even disappears with time completely on its own. Leaves look similar to a Magnesium(Mg) deficiency but remember that this is an immobile element so it will show up on the newer and smaller leaves. Leaves turn yellow while the veins remain green.
Iron(Fe) will also show up usually with higher PH levels. You can also help your plant by increasing the drainage if you are a soil grower and by increasing the temperature of the plants root zone.
Iron(Fe) toxicity is rare but it can happen. Toxicity does not usually damage marijuana plants but it can interfere with its uptake of Phosphorous(P). You can spot it by the leaves turning a bronze color with little dark brown spots on the leaves.
The experts at our Hydroponic Stores in Paso Robles, San Luis Obispo, and Grover Beach have plenty of products both organic and chemical to handle this problem.
Nick always has something to fix the problem and for this he has Botanicare Plus. A lot of his customers constantly mistake iron deficiency for another problem like Magnesium (Mg). By using a good CalMag product the problem is fixed 99% of the time. By using Botanicare Plus the plus is the addition of Iron (Fe) which takes care of things all the way around.
Healthy Harvest hasn't seen too many cases of Iron (Fe) deficiency in soil but he has seen Iron (Fe) problems in hydro gardens with reservoirs. You should always change your water ever 7 days but growers can sometimes be lazy and this could cause an Iron (Fe) problem. Another problem that could come up is if your pump that you're using to get the nutes up to your plants is one of the styles with a large magnet in it. If it is you might want to change your reservoir every 5 days. The big magnet can believe it or not effect your Iron (Fe) and hold it back. It does no good hanging out in your reservoir and not heading up the line into your plants. If you do get a deficiency Grady recommmends foliar feeding with Botanicare CNS17. It will instantly clear up your problem with not only Iron (Fe) but all of your micro-nutrients.