Agricultural grade ferrous sulfate is widely used, but there are many points for attention in the process of use.

1. Ferrous sulfate should be sealed and kept away from moisture. Once it is damp, ferrous sulfate will gradually oxidize into trivalent iron which is not easy to be absorbed by plants, and its effectiveness will be greatly reduced;

2. Ferrous sulfate for flowers should be prepared and used on site. It is unscientific to prepare a lot of ferrous sulfate solution for repeated application for a long time.

3. The dosage of ferrous sulfate should not be too large and the frequency should not be too frequent. Generally speaking, 5g to 7g ferrous sulfate should be added to pot soil, and 0.2% to 0.5% should be applied for irrigation or spraying. If the dosage is too large and the times of topdressing are too frequent, the plants will be poisoned, the roots of flowers will turn gray and black and rot, and the absorption of other nutrients will be affected because of its antagonistic effect;

4. Ferrous sulfate should be prepared with suitable water. Ferrous sulfate is easy to become trivalent iron oxide sediment in calcareous alkaline water, which is difficult to be used by plants. It is best to use rain, snow water or cold boiled water to prepare ferrous sulfate. If you have to use alkaline water, add 1g to 2g potassium dihydrogen phosphate into every 10 liters of water to make it a slightly acidic "improved water". Adding 3% vinegar in alkaline water also has better effect;

5. When ferrous sulfate is mixed in alkaline soil, appropriate potassium fertilizer should be applied, but not plant ash. Potassium element can promote the effectiveness of ferrous sulfate because it is conducive to the absorption of iron in plants;

6. The application of ferrous sulfate solution to hydroponic plants should avoid sunlight. If the sun shines on the nutrient solution containing iron, the iron will deposit in the solution and reduce its effectiveness, so it should be placed away from the light.

7. The mixed application of ferrous sulfate and decomposed organic fertilizer solution had a good effect.