You may be reading a lot in the news lately about copper. Thieves are stealing it off of houses
, off of working power grids
, and even churches
. While thieves looting copper gets the headlines, how much have you read about adding copper to your fertility program? The lack of copper in your soil could be costing you big money. Yield reductions of 70-100% have been recorded due to copper deficiency. In copper deficient Canadian soils, inclusion of copper could increase yields by 100 million dollars for Canada alone!
Copper deficiency has been found throughout the world in all climatic zones where crops are grown or animals kept on farms. Its incidence varies according to soil, crop, livestock and management factors. In particular it can occur in crops growing on soils with a sandy texture, on those rich in organic matter and on calcareous soils, but other soil factors can also cause a deficiency.
Wheat, barley and flax are not very efficient in copper uptake, and typically respond well to copper, though Alfalfa has been found to respond well too.
Symptoms of Copper Deficiency
Wheat and barley deficient in copper are more likely to lodge. Copper deficiency can delay flowering by up-to two weeks and result in pollen sterility. Pig tailing and leaf yellowing in young tillers is a common sign of copper deficiency in wheat, barley and oats.
Reasons for Deficiency
Copper is pretty immobile in the soil. Of all the copper on a soil test, an average of 50% is insoluble and unavailable, 30% is bound to organic sites, 15% is in an oxide form, and only 5% is available for plant uptake.
Soils are considered deficient in copper when they contain less than 2 ppm. Howvever, even when soils have adequate copper (30-50 ppm) other factors such as high pH, and organic matter can reduce copper availability. Soil pH above 6.4 can limit copper uptake. Copper concentration in soil solution decreases sharply as pH increase. Copper is 10 -100 times more available at a 6 pH than at 7.
Copper is more strongly bound to soil organic matter that any other micronutrient. Copper deficiency is primarily found on high organic matter soils. Applications of copper not only increase crop production but also reduces the decomposition of organic matter, increasing the sustainability and health of the soil.
In addition to soil factors, other fertilizer can interact with copper. High rates of nitrogen can accentuate copper deficiency. Soils high in iron, manganese, molybdenum or zinc can also limit plant uptake of copper. Copper is most strongly adsorbed to iron and aluminum, another reason to avoid by-product liming materials. Copper toxicity is rare and generally only occurs with long-term use of copper pesticides in orchards or from applications of by-products and sludges high in copper.
Adding Copper into your fertilizer program
Soil incorporation of copper is the best long term solution to solving copper deficiency. Copper sulfates, oxysulfates and our forth coming MicroHume product are great sources of dry granular copper to add to a dry program. While foliar applications should be used on crops that are copper sensitive or need an immediate dose of copper. Wheat does not respond to foliar applications of copper after anthesis, and may actually reduce yield a