A Powerful Tool for Magnesium Sulfate Sulfate Foliar Spray: Important Precautions You Must Know! BY:Lina

Magnesium sulfate, as a high-quality foliar magnesium fertilizer, is widely used to correct magnesium deficiency symptoms in crops. However, foliar spraying is not a "one-and-done" process; mastering the correct application method is crucial for maximizing results. Today, we outline five key precautions for magnesium sulfate foliar spraying to help you increase yields scientifically.

As a foliar fertilizer, concentration control is paramount for magnesium sulfate. The commonly recommended concentration is 1%–2% (i.e., 1–2 kg of magnesium sulfate diluted in 100 liters of water). Too low a concentration will have little effect, while too high a concentration can easily cause leaf burn, resulting in scorched edges, spots, and other fertilizer damage. It is recommended to test on a small number of leaves first to confirm safety before large-scale spraying.

The timing of spraying directly affects absorption efficiency. The optimal application period is during the seedling stage, before flowering, and during the young fruit stage or tuber enlargement stage (for crops such as potatoes). Avoid spraying at midday when plants are severely wilted or during periods of high temperature and drought. Simultaneously, when crops show obvious symptoms of magnesium deficiency (such as chlorosis between veins in older leaves), spray 2-3 times consecutively, with an interval of 7-10 days between each application.

Special attention must be paid to compounding contraindications when mixing magnesium sulfate with other pesticides or foliar fertilizers. Avoid direct mixing with preparations containing calcium (such as calcium nitrate, sugar alcohol calcium), copper (such as Bordeaux mixture, copper hydroxide), or high concentrations of phosphorus, otherwise precipitation or antagonistic effects may occur, reducing fertilizer efficacy or even causing phytotoxicity. If compounding is necessary, it is recommended to first mix a small amount and observe the mixture to confirm the absence of precipitation or flocculation before use

The efficiency of magnesium ion absorption by leaves is closely related to the wetting time. Under ideal spraying conditions, the fertilizer solution should remain on the leaf surface for at least 30-60 minutes without drying. Therefore, it is recommended to spray in the windless evening (after 4 pm) or early morning when the dew has not yet dried. The spray droplets should be fine, and the focus should be on the undersides of the middle and lower older leaves, as magnesium is mobile within the plant, and magnesium deficiency first manifests in older leaves.