Forage enrichment with copper and zinc in beef grazing systems in Argentina

The presence of trace elements in water and soils, their absorption by plants, and their transfer to the food chain, is a phenomenon that has been studied in different regions around the world. In Argentina, few studies exist regarding trace element content in soils, and the studies on forages are furthermore scarce. The interest to quantify the levels of trace elements in cattle forage lies in the intrinsic connection between the quality of forage and the nutritional (i.e. Cu and Zn) aspects of cattle health and products for human consumption. Feed lots use feed, which incorporates core minerals whose basic components are Fe, Se, I, Mn, Co, Cu, and Zn. The excess of these trace elements are eliminated through the feces into the environment, therefore, the use of manure from these systems, as a source of organic fertilizer, could reduce environmental contamination, and supplement soils, in areas which are naturally deficient in these micronutrients, for forage growth intended for livestock consumption. Soils from different areas in Argentina were characterized, mainly for their Cu and Zn content. Soil–plant transfer of these trace elements to natural forage was analyzed for agricultural soils with higher content of micronutrients. On the other hand, pot experiments were performed for the enrichment of the forage species, Lolium perenne (ryegrass), with Cu and Zn through fertilization with bovine feces spiked with known concentrations of these trace elements. Soils from copper‐deficient areas used for livestock breeding were used in these experiments. Differences in Cu and Zn concentrations were observed between the fertilized and non-fertilized reactors, while there were no differences found in the Cu and Zn concentrations considering the method of fertilization (homogenization or superficial). These results show that manure from feed lots may be used for forage enrichment with micronutrients.

► Spatial variation in Cu and Zn contents in soils from the Chaco Pampean plain. ► No linear relationship between soil concentration and plant concentration. ► Forage Cu and Zn enrichment reaching levels over the limit of deficiency. ► Manure from feed lots in Argentina may be used as fertilizers. ► Manure from feed lots may be used to compensate Cu and Zn deficiencies.