Influence of cadmium contamination on biomass production and mineral nutrition of tropical grasses

Cadmium (Cd) is a toxic heavy metal that disrupts plant nutrition and reduces biomass production. This study evaluated the effects of Cd contamination on biomass yield, nutrient status, nutrient use efficiency, and the phytoextraction potential of two tropical forage grasses. A greenhouse experiment was conducted in a randomized block design with a 3 × 2 factorial arrangement, including three Cd levels (0, 2, and 12 mg kg−1) and two forage species (Megathyrsus maximus cv. Mombaça and Urochloa brizantha cv. Marandu). Plants were grown in two soils with contrasting physicochemical properties (Typic Hapludox and Typic Quartzipsamment), both limed and fertilized. Cadmium exposure altered nutrient concentrations in plant tissues. Concentrations of N, P, K, S, Cu, and Zn increased with Cd contamination, while nutrient use efficiency declined, particularly at higher Cd levels. These effects were mainly attributed to a concentration effect caused by reduced biomass. U. brizantha showed greater tolerance to Cd stress, with higher biomass production, improved nutrient use efficiency, and greater removal of bioavailable Cd from the soil compared with M. maximus. The results highlight the importance of species selection and proper soil and nutrient management for phytoremediation of Cd-contaminated soils.