Mobility in soil and availability to triticale plants of copper fertilisers

The mobility and availability to plants of copper (Cu) applied through inorganic and organic fertilisers can be important for crop production and also in terms of its environmental impact. Column and greenhouse experiments were conducted on a Typic Xerorthent soil (pH 7.09, sandy clay loam texture with moderate permeability) to study the relative migration and extractability of Cu sources in a reconstructed soil profile and the response of a triticale crop (X Triticosecale Wittmack) to the Cu supplied. The soil Cu status and quantity of Cu in the leachates were established in the soil columns according to layer depth and experimental time. Most of the Cu applied though natural (Cu-lignosulfonate, Cu-gluconate, Cu-galacturonatemonogluconate, Cu-bis(ethoxydihydroxydiethylamino)sulfate) and inorganic (Cu-oxychloride) fertilisers remained in the top soil and Cu-HEDTA migrated to a soil depth of 20cm. Only when Cu was applied as Cu-EDTA and Cu-DTPA-HEDTA-EDTA did a large percentage of Cu remain in the top soil, initially in the water soluble fraction. The Cu associated with this fraction migrated and became distributed throughout the soil column, producing significant Cu losses due to leaching. For a 2.120 pore volume of collected leachate and an experimental time of 200 days, the leaching rates were respectively 23% and 51% of the total amount of Cu applied. The high potential availability of Cu to plants from these two sources, and to a lesser extent for Cu-lignosulfonate (applied at 2 and 3mg Cu kg(-1) rate), were correlated with the higher concentrations and uptakes of Cu by triticale grain. The advantage of this last source is that it does not produce losses due to leaching.