ADUBAÇÃO NITROGENADA E FOSFATADA E USO DE POTÁSSIO NA INDUÇÃO DE RESISTÊNCIA A DÉFICIT HÍDRICO EM Acrocarpus fraxnifolius Wight & Arn.

Abstract

In a context of climate change, water restriction and nutritional deficiency are factors that affect the growth and development of plant species, including forest species such as Indian cedar. Therefore, the objective of the present study was to evaluate the morphological, anatomical, physiological and productive characteristics of Acrocarpus fraxinifolius seedlings in response to nitrogen and phosphate fertilization, using urea and triple superphosphate fertilizers in the planting furrow, in addition to evaluating the efficiency of rustification potassium fertilizer use to tolerate the effects of water deficit. The first and second chapters consisted of 2 different experiments in a randomized block design (DBC) where 5 nitrogen doses (0; 11; 22; 45 and 90 g of N per plant) and 5 phosphorus doses (0; 20; 40; 80 and 160 g of P2O5 per plant) were applied in the planting furrow in a dystrophic Red Oxisol. For the last chapter, an experiment was carried out in a 2x5 factorial scheme, testing 2 potassium rustification fertilizations (partial and complete) and 5 water replacements in the soil (30; 40; 50; 60 and 70% of field capacity (CC)) in pots in a controlled environment. The parameters measured during the experiments were: shoot height, stem diameter, diameter at ground level, crown diameter, leaf length, leaf width, leaf area, diameter at breast height, cylindrical volume of wood with bark, accumulation biomass, gas exchange, chlorophyll a fluorescence, leaf water potential, electrolyte release rate, chlorophyll indices, Dickson quality index, robustness index, content and accumulation of N, P, K, Ca, Mg and S , micromorphometry and leaf anatomy. Nitrogen fertilization increased growth parameters, chlorophyll indices, photosynthetic rate, N accumulation in leaves and provided a greater cylindrical volume of wood in the first year with better results at a dose of 22 g of N per plant in the planting furrow. The phosphorus doses applied in the planting furrow showed an increasing response to the morphological, physiological and production parameters evaluated, with greater technical efficiency at a dose of 80 g of P2O5 (133 kg. ha-1) applied in the furrow per plant. The water stress of plants subjected to 30% of field capacity showed reductions in the photosynthetic rate, which consequently negatively affected the other morphophysiological variables. Potassium rustification fertilizers in the production of Indian cedar seedlings allowed better post-planting establishment, providing an increase in water use efficiency, photosynthetic rate, chlorophyll levels and total biomass production, becoming an important management tool for commercial plantations.