Crescimento, biomassa e nutrientes do Eucalyptus saligna Smith sob manejo dos resíduos da colheita e fertilização

Abstract

Intensive forestry has proposed the maximum use of resources produced in forest ecosystems, however, studies evaluating the management of havesting residues and the replacement of nutrients in the form of fertilizers still lack information to assess the nutritional sustainability in the system. Given this, the present study aimed to evaluate the growth, biomass and nutrients for Eucalyptus saligna to 22 months age. The experiment was conducted in the Horto Florestal da Barba Negra, located in the city Barra do Ribeiro / RS, applying a randomized block design with 3 repetitions. Four treatments were applied: T1 = presence of havesting residues in the field of cultivation, T2 = removal of the havesting residue without nutritional replacement, T3 = removal of havesting residues and replacement of 50% of the nutrients amount removed with the residues, and T4 = removal of havesting residues and replacement of 100% of the nutrients amount removed with the residues. The chemical characteristics were evaluated, and the soil nutrients stock during 15 months of planting was estimated. For dendrometric evaluation, it was measured the DBH and the total height of the trees at 7, 12, 18 and 22 months of age. The leaf area index and aboveground biomass were determined using as reference the average DBH of trees in each of the growing conditions. The nutrient use efficiency (NUE) was calculated as the ratio between the biomass and the amount of nutrient of each biomass component. The effective CEC, in the layer of 20-40 cm depth was the only chemical attribute of the soil that showed significant difference, with higher levels in the condition of waste removal and replacement of 100% of the nutrients. The greatest growth of Eucalyptus saligna was observed with waste removal and replacement of 100% of the nutrients. The leaf area index and aboveground biomass were not affected by waste management and replacement of nutrients at 22 months age. The allocation of aboveground biomass followed the same order: wood > green branches > leaf > bark > dry branches. However, the treatments influenced the order of nutrient accumulation in the different components of biomass. Wood was the component that showed higher values of NUE for most nutrients analyzed.