Banca de QUALIFICAÇÃO: YAN PATRICK MOITA CID

GROWTH AND NUTRITION OF BRAZILIAN MAHOGANY PLANTS (Swietenia macrophylla King.) IN SOIL CONTAMINATED BY COPPER AND USE OF BIOCARCOAL AS A MITTENATOR

nutritional assessment; heavy metal; biochar; forest species.

Copper (Cu) is an essential micronutrient for the growth and development of plants, acting in several physiological processes and is found naturally in soils. However, due to human activities, mainly mining and agriculture, its soil content has increased. In plants, excessive amounts of copper limit plant growth, development and production. Therefore, the use of biochar appears to be a viable alternative to making elements unavailable in concentrations that are toxic to plants. The present study aims to evaluate the growth and nutritional status of Brazilian mahogany (Switenia macrophylla King.) plants exposed to Cu toxicity in the soil and the use of biochar as an attenuator. The experiment was carried out in a greenhouse at the Universidade Federal Rural da Amazônia - Campus Belém. The experimental design was in randomized blocks, which consisted of the control treatment (without Cu), three doses of Cu (200, 400, and 600 mg Cu kg-1), three levels of açaí seed biochar (BCA) (0%, 5% and 10%) proportional to the amount of soil used in the pots, totaling 60 experimental units and one forest species, Brazilian mahogany. The seedlings were produced through seminal propagation in a controlled environment, to ensure that they developed and germinated uniformly, and after that they were transplanted to the experimental units and were cultivated for 90 days after definitive planting. Next, the plants were divided into leaves, stem and roots, and dried in an oven at 65 °C until they reached a constant mass, and the dry mass of the aerial part (MSPA) and the dry mass of the stem (MSPA) were determined using a precision scale. MSC) and root dry mass (MSR). The results showed that there was a significant interaction between the doses of copper (Cu) and the concentrations of açaí seed biochar (BCA) for the variables leaf dry mass (MSF), stem dry mass (MSC) and root dry mass (MSR). In the total biomass variable, there was a significant isolated effect for Cu doses and BCA concentrations. In MSF, the use of BCA at a proportion of 5% achieved a greater quantity of MSF when a dose of 400 mg kg-1 Cu was applied. Plants with 10% BCA showed an increase in MSF at a concentration of 200 mg kg-1 Cu in the soil compared to plants that did not receive any concentration of Cu. In MSC, plants with 5% BCA at three concentrations (200, 400 and 600 mg kg-1 Cu) showed an increase when compared to control treatments without Cu doses. In plants with 10% BCA, only the concentration of 400 mg kg-1 Cu differed from plants with the treatment without Cu, showing growth. In MSR, an increase in concentrations of both 200 mg kg-1 Cu and 400 mg kg-1 Cu was observed when applying 5% biochar, when compared to plants where Cu was not used in the soil. In total biomass, plants with doses of 200, 400 and 600 mg kg-1 of Cu demonstrated an increase when compared to the control treatment. In the proportions of açaí seed biochar (BCA) in total biomass, there were no differences for the proportion of 5% BCA compared to plants that did not receive BCA, however, with the addition of 10% BCA there was a reduction in biomass total. BCA was able to mitigate the effects of Cu toxicity. BCA at 5% improved plant growth, reducing Cu activity up to a concentration of 600 mg kg-1 Cu.