Organic Matter Application Can Reduce Copper Toxicity in Tomato Plants

Copper fungicides and bactericides are often used in tomato cultivation and can cause toxic Cu levels in soils. In order to combat this, organic matter can be applied to induce chelation reactions and form a soluble complex by which much of the Cu can leach out of the soil profile or be taken up safely by plants. Organic acids such as citric, fulvic, and malic acids are contained in organic matter, and complex well with Cu. Both the chelation reaction and the effectiveness of soil organic matter in the chelating process are pH dependent, and generally a more alkaline soil will be less affected by high Cu levels. In addition to organic matter application, lime may also be added in order to raise the pH and aid the process by which Cu is removed. Other benefits are also derived from soil organic matter application in addition to soil remediation. Organic matter improves soil structure, exchange capacity, and water holding content. Application of organic matter is thus a viable option for restoring toxic Cu soils.