Chemical speciation of copper and manganese in solution of a copper-contaminated soil and young grapevine growth with amendment application

Copper (Cu)-based fungicide application to control foliar diseases in grapevine (Vitis vinifera L.) can increase soil Cu availability. Brazilian soils have high natural Cu and manganese (Mn) concentrations, increasing the potential for toxicity to grapevine plants. Application of amendment substances can reduce the concentrations of toxic chemical species of Cu and Mn in soil solution, especially for the soils grown with young plants. We evaluated the chemical speciation of Cu and Mn in soil solution and young grapevine growth using a contaminated soil with amendment application. Grapevine seedlings of Paulsen 1103 rootstock were grown for 12 months on an old vineyard (> 30 years of cultivation) soil without (control) and with vermicompost or limestone application. Grapevine dry matter, root morphological characteristics, and plant tissue Cu and Mn concentrations were evaluated. The cation and anion concentrations, dissolved organic carbon, pH, and chemical speciation of Cu and Mn in soil solution from different soil layers were analyzed. Vermicompost application did not reduce Cu and Mn phytotoxicity, and grapevine plants died after winter pruning. High soluble Mn concentration in soil (5.56 mg L-1 in 0-45 cm soil layer) and Mn concentration in plant tissue at pruning (380.8 mg kg-1) might be the primary cause of plant death. Limestone application reduced Cu2+ and Mn2+ chemical species in soil solution, thereby increasing plant growth. The Cu2+ and Mn2+ species were negatively correlated (P < 0.05) with grapevine shoot production at pruning (r = -0.92 and -0.97, respectively) and at the end of the trial (r = -0.73 and -0.51, respectively). Limestone application increased grapevine shoot and root dry matter production by 36% and 41%, respectively, while also presenting the highest root length and volume in the 5-10 cm soil layer. Limestone application is a viable and profitable alternative for reducing soil Cu and Mn availability and their phytotoxic effects.

Automated summary

Copper (Cu)-based fungicide application can increase soil Cu availability, but this can be problematic in soils with high natural Cu and manganese (Mn) concentrations, such as Brazilian soils. Applying amendment substances, like limestone, can reduce the toxic species of Cu and Mn in soil solution, leading to improved grapevine growth. In this study, vermicompost application did not alleviate Cu and Mn phytotoxicity, while limestone application significantly increased grapevine shoot and root dry matter production.