Ferrous sulfate deficiency in a plant is indicated by the yellowing or whitening of leaves and usually occurs on new growth, although it can spread to old growth if the deficiency is severe. This happens because of a high alkalinity (pH) in the soil that makes the ferrous present unavailable to the plant. Plants use ferrous to create chlorophyll and to photosynthesize. Without the green chlorophyll, the leaves become yellow and then go brown around the edges as they die.
1. Use a pH test kit to test your soil. These can be found at most nurseries or hardware stores and they're easy to use. Place a sample of your soil in the test tube, add in the testing solution, then compare it to the enclosed color chart.
2. Determine which chelated ferrous fertilizer is needed for your garden's alkalinity. There are several formulas and each is recommended for a different pH. Read the label and look for a high percentage of chelated ferrous.
3. Mix your liquid ferrous fertilizer in a pump-up sprayer. Follow the products directions for foliar application.
4. Spray the plants that are showing ferrous chlorosis. It's best to spray ferrous sulfate solutions in the evenings so wet leaves aren't burned by the heat of the sun.