When is the best time to apply micronutrients?

"The timing of micronutrient application is what separates bumper harvests from disappointing returns. When using soil amendments such as zinc sulfate, apply them before planting to give roots access to nutrients as early in the season as they can. Simply applying foliar sprays when plants are in early vegetative growth leads to more efficient absorption of the solutions by leaves because the leaf area is rapidly developing. Timing is even more important during flowering. Copper and boron applications need to be timed to coincide with pollen development."

Applications to the soil must have pH values lower than 6.5, or iron will not be available for plant uptake. On several occasions, I rescued soybean fields by injecting iron EDDHA into irrigation water during flowering. To enhance the apple fruit set, make a foliar application of manganese at bud break; if you delay the application until the petal falls, you will lose the ability to absorb the manganese.

During the flowering stage, micronutrient precision is especially important. For broccoli, boron is required at the first flower clusters, as late boron is correlated with hollow stems. Citrus care requires sprayed zinc during bloom drop. In Florida, a grower increased orange yield two-fold by spraying at a 50% open flower stage.

Evaluate soil moisture levels before applying any products. Dry soil conditions may segregate manganese. Wet soil conditions can turn copper into a poison for plants. I educate the field staff to time foliar sprays 2 days post-irrigation for greatest region uptake. Be consistent with tracking growth stages, for example, corn can take up zinc optimally when it is in V4-V6, not tasselling.

Read the full article: 7 Essential Micronutrients for Plants: Complete Guide