Copper sulfate can be used as a fertilizer or fungicide. It is commonly used by gardeners and commercial farmers to prevent problems with fungus or mold. The effects of copper sulfate on plants may be negative or positive. The copper status of the soil, together with the frequency of application and quantity of copper sulfate applied, will determine the effects of copper sulfate on plants.
Used in an area of copper-deficient soil, copper sulfate enriches the soil and provides an essential nutrient to growing plants. When soil is copper-deficient, young plants may develop chlorosis, a condition in which leaves yellow due to lack of chlorophyll. Copper deficiencies can also cause stunted or atypical growth; young plants in very nutrient-deficient soil may simply die. Wilting, lack of flowers and reduced fruit harvest are all likely effects of copper-deficient soil. Copper sulfate prevents these problems. Test soil regularly, and apply copper sulfate as needed in a spray or fertilizer preparation.
Copper sulfate has anti-fungal properties, and is a key ingredient in some commercial fungicides for farm and garden. These fungicides are typically mixed with water and either lime or soda ash, then sprayed onto the plants. The effect of such a copper sulfate fungicide is prevention or reduction of fungal infections that can disease or destroy the plant. If a plant is already affected by fungus, copper sulfate fungicides may be effective in removing the fungus. This use is effective only if the fungicide is applied soon after fungal infection occurs.
When copper sulfate is applied excessively, soil copper levels become toxic to plants. Plants growing in soil that has too much copper may develop discolored leaves as a result of iron chlorosis. Typically, leaves will become dark green, then turn white as chlorophyll fails to enable proper photosynthesis. Additionally, copper toxicity can cause damage to the roots of plants. When roots are damaged, plants are likely to grow more slowly, wilt or even die.
Effects on Fruit
In fruiting plants, copper affects the sugar content and flavor of the fruits produced. The effects of copper sulfate are most pronounced in blueberry, tomato, watermelon, onion, parsnip, lettuce, beet, carrot, cabbage, eggplant, celery and spinach plants. In general, water accumulation in a plant is lower, and therefore its taste is sweeter, when its conductivity is low. Excess copper sulfate increases conductivity, reducing the sugar concentration and flavor intensity of the fruit. If you want to grow sweet fruits that are not watery, ensure you are not over-applying copper sulfate to your plants.
- University of Illinois Extension: Chlorosis
- Spectrum Analytic: Copper
- Best of Growing Edge: Popular Hydroponics and Gardening for Small Commercial Growers; Tom Alexander
- Sweet Potato DiagNotes: Copper Toxicity
- Copper Development Association: Uses of Copper Compounds: Copper Sulphate's Role in Agriculture
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