Erosion control can prevent deficiency of zinc by maintaining the topsoil. Zinc deficiency can be prevented by application of zinc fertilizer to the soil. Foliar sprays can be useful to correct a deficiency after the symptoms have appeared provided this is done early in the growing season. For materials and rates to correct a deficiency, consult the corn section under Micronutrients. Zinc Soil Test Interpretation Copper soil tests are quite unreliable on Ontario soils but plant analysis is useful.
Copper is unlikely to be deficient on mineral soil, except perhaps on very sandy soils.
Copper deficiency does occur on organic soils and is best diagnosed by plant analysis. Boron is required on some soils for alfalfa. Boron deficiency usually occurs in dry weather so that response is erratic. Thus it has not been possible to develop a reliable soil test. Plant analysis is useful as a predictor of boron requirements as are visual symptoms on the plants.