Soil Management and Fertilizer Use:
Micronutrient Fertilizers

Excerpt from Agronomy Guide for Field Crops (Chapter 2)

Order OMAFRA Publication 811: Agronomy Guide for Field Crops

Table of Contents

1. Introduction
2. Manganese
   • Preventing and Correcting Manganese Deficiency
   • Manganese Soil Test Interpretation - Table 2-13
3. Zinc
   • Preventing and Correcting Zinc Deficiency
   • Zinc Soil Test Interpretation - Table 2-14
4. Copper
5. Boron
6. Updates on Soil Management and Fertilizer Use: Micronutrient Fertilizers
7. Related Links...

Introduction

Micronutrient elements should not be combined with insecticide or fungicide sprays unless the manufacturer's directions indicate that this may be done.

Micronutrient elements should be applied only on competent advice or where experience has proven their application to be necessary. Soil or foliar applications can be made. Soil applications are generally made at soil-preparation time, and foliar applications are applied during the growing season. A sticker spreader should be included in micronutrient sprays.

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Manganese

Preventing and Correcting Manganese Deficiency

The general symptom of manganese deficiency is interveinal chlorosis of leaves, which begins on the younger foliage. Later, the whole plant may be affected. Cereals show manganese deficiency as a general yellowing and stunting, occasionally with grey specks on the leaves. The crops most susceptible to manganese deficiency are soybeans, edible beans and cereals.

Manganese is less available at high soil pH, so it is important not to add more lime than is needed to correct soil acidity. For materials and rates to correct a deficiency, consult the sections on Soybean Micronutrients and Cereals Micronutrients. Interpretation of the manganese soil test is found in Table 2-13. Manganese Soil Test Interpretation.

¹These values are indices of manganese availability based on extractable soil manganese and soil pH.

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Zinc

Preventing and Correcting Zinc Deficiency

Corn is the main crop showing zinc deficiency in Ontario. Zinc deficiency has been reported in beans in other areas but it appears to be rare in Ontario. High phosphorus in the soil and/or in the fertilizer can cause or increase the severity of zinc deficiency. Apply only the recommended amount of phosphorus. Use of animal manures can prevent or reduce zinc deficiency. Erosion control can prevent deficiency of zinc by maintaining the topsoil.

Zinc deficiency can be prevented by application of zinc fertilizer to the soil at a rate of 4 kg/ha (3.6 lb/ac). Up to 14 kg/ha (12.5 lb/ac) can be broadcast, and this will correct a deficiency for 3 years, but not more than 4 kg/ha (3.6 lb/ac) should be banded. Foliar sprays can be useful to correct a deficiency after the symptoms have appeared provided this is done early in the growing season. For further details on materials and rates to correct a deficiency, consult the section Secondary and Micronutrients, in the corn chapter. Interpretation of the zinc soil test is found in Table 2-14. Zinc Soil Test Interpretation.

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¹These values are indices of zinc availability based on extractable soil zinc and soil pH.

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Copper

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. When organic soils are first brought into cultivation, copper should be applied to the soil at 14 kg/ha (12.5 lb/ac) for each of the first 3 years.

Boron

Boron is required on some soils for alfalfa, particularly on sandy or gravelly soils with low water-holding capacity. Deficiencies are more common in central Ontario than in the rest of the province. Boron deficiency occurs most frequently during dry weather and the response to boron may be inconsistent. 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. For rates of boron to correct a deficiency, consult the section Micronutrients.

Because boron is needed only in very small quantities, and since an overdose is toxic, extreme care should be taken in its use. Boron deficiency has not been diagnosed in cereals, peas and beans in Ontario, and boron applications to these crops, or applied to other crops in the year preceding them, can be toxic. Boron should not be banded.

Iron and molybdenum have not been found to be deficient in field crops in Ontario.

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Updates on Soil Management and Fertilizer Use: Micronutrient Fertilizers

No updates available at this time.

Related links...

• Soil Fertility & Crop Nutrition

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