Many of the fertilizers and pesticides commonly used bring copper to the soil with risks of accumulation and phytotoxicity.
The soils can receive heavy metal inputs, both from atmospheric depositions, but also with the contribution of fertilizers and plant protection products. In the long run, the accumulation of these elements, generally well retained by soil, can negatively affect the fertility of the soils or worsen the quality of agricultural products, or contaminate surface and groundwater.
Many metals such as copper and zinc end up being harmful at the level of high soil concentration for microbial biomass and for higher organisms such as earthworms and plants. Other metals are not essential (Cd, Hg, Pb) and for this reason they are potentially toxic even at low concentrations. The sensitivity of different cultures to the toxic effect of copper varies widely. It is difficult to evaluate the phytotoxicity of this element, as it accumulates in the roots, damaging in the first place this organ not directly visible.
Mineral and organomineral fertilizers may contain copper resulting from the raw materials used for their production. In sewage sludge, on the other hand, copper is concentrated which is removed from the water subjected to the purification treatment, and which can therefore derive from the most varied domestic and industrial sources.
Among the agricultural sources of contribution to copper soils we must include plant protection products based on this metal. Important inorganic anticryptogamic agents, especially used for the control of downy mildew, are copper-based compounds. In fact, several studies have shown important copper accumulations in vine-grown soils, both for the superficial layer and for greater depths, and have credited the lack of environmental sustainability of cupric treatments in viticulture, in particular in the biological defense regime.
With respect to the copper quotas applied to the soil, it is important to consider the high general capacity of the soils to retain (and therefore accumulate) heavy metals, without forgetting that a total amount of metal in the soil can transfer to the percolating or superficially flowing waters.
From these considerations derives the need to deepen the studies on the real toxicity of copper in soils, in particular for those that potentially have characteristics favorable to the risk of phytotoxicity (low amount of organic substance).
Scientific research has dealt little with the issue, but the results obtained seem to agree that this metal has negative effects on most of soil species, leading to a decrease in the biodiversity of the agricultural environment, an effect that increases over time due to the accumulation of copper. The presence of bacteria and fungi in the soil, but also on the aerial parts of the plant, can represent a particularly effective defense mechanism against microscopic plant parasites and enrich the soil with mineral elements, fundamental for the crops; Copper-sensitive animals, such as earthworms and snails, can improve the texture of the soil, creating channels for aerating the roots and promoting the decomposition of organic matter, improving soil quality. Copper also has a documented insecticidal action and its accumulation in the environment could lead to the removal of coccinellids and pollinators.
This is why when we talk about organic farming we have to be careful, because doing 40-45 copper treatments on a plant has little biological!!.