Crescimento e desenvolvimento de plantas de milheto, milho e sorgo em rejeitos de mineração do desastre de Mariana-MG e o efeito benéfico da adição de vermicomposto

Abstract

Given the accident that occurred in 2015 in Mariana-MG, there was a great concern in restoring the environment, as the waste devastated an extensive area. In this way, this study aimed to evaluate the germination, and initial growth and development of three plant species: DKB 390 maize (Zea mays L.), BRS 1502 (Pennisitum glaucum L.) millet and BRS 332 (Sorghum bicolor) sorghum; as well as the effect of the addition of vermicompost to the mining tailings on the plant growth promotion. Thus, three experiments were conducted. The experiments I and II were performed using the following treatments: 0T (100% sand), 25T (25% tailings + 75% sand); 50T (50% tailings + 50% sand); 75T (75% tailings + 25% sand) and 100T (100% tailings). There were evaluated seed germination and initial growth in Experiment I, whereas in Experiment II there were evaluated plant growth, photosynthetic efficiency, metal accumulation and root morphology of plants in V3 developmental stage. It was observed that tailings did not affect seed germination and initial growth of all plant species. However, the morphophysiological changes of plants at V3 stage were different between species, with modifications in plant growth and biomass accumulation and root morphology. The experiment III was performed with the treatments: mining tailings (Tailings), mining tailings + vermicompost in proportion (20g of worm castings dm-3 tailings) (Tailings + vermicopost) and a reference soil (Soil). The evaluations started when the plants reached the V3 stage, and were performed biweekly, assessing plant growth, gas exchange and chlorophyll efficiency. At the end of the experiment, plant biomass, metal accumulation and root morphology were evaluated. The addition of vermicompost increased shoot and root dry biomass in all of the species. Those plants showed higher root length, volume and diameter, favoring the absorption of macronutrients P, K, Mg and Ca and micros B, Fe and Zn. It was also observed higher gas exchanges and improved plant growth. In summary, root growth is primarily responsible for the success of species grown in mining tailings, despite the plant developmental stage.