Interação nutricional em mudas de baru e desenvolvimento de plantas sob calagem e doses de P em campo

Abstract

Baru is one of the most promising Cerrado native species considering the recovery of degraded areas and use of fruits. However, the scarcity of information about its nutritional requirements can interfere on their implementation. The growth and mineral nutrition of baru (Dipteryx alata) were evaluated in a controlled environment by the interaction between nutrients and plant development in the field under liming and fertilization. Three experiments were conducted in pots, at the greenhouse of DCF of UFLA, in Lavras-MG, and two others in the field. Growth and nutrition of the seedlings were analyzed according to the combined fertilization of N and S. The substrate was the subsurface layer of 20-40 cm of a dystrophic Yellow Latosol, applying doses of S (0, 30 and 60 mg dm -3 ) and N (0, 50, 100, 200 and 400 mg dm -3 ) as magnesium sulfate and urea, respectively, using a 3 x 5 factorial system. In experiment 2, doses of P (150 and 300 mg dm -3 ) and B (0, 0.25, 0.50, 1 and 2 mg dm -3 ) as triple superphosphate and boric acid, respectively, in a 2 x 5 factorial system. In experiment 3, the effect of doses of S (0, 25, 50, 75, 150, 225 and 300 mg dm -3 ) applied as magnesium sulfate was evaluated. The morphological characteristics of shoot height, root collar diameter, leaf and leaf numbers were measured after 90 days. Subsequently, nutrient content was analyzed at the UFLA DCS PMNL. Experiments 4 and 5 were conducted at the Experimental Farm of the EPAMIG Sul de Minas (Farias Unit), in a Hap Cambish Haplotype Tb eutrophic. For experiment 4, it was used four limestone applications aiming at raising the natural base Saturation (V%) of the soil from 6.7 to 35, 55 and 75%. As for Experiment 5, five dosages of P (0, 10, 20, 40 and 80 g of P₂O₅) were applied. Plant height and stem diameter were evaluated at 48, 54, 60 and 70 months after planting. At 70 months, freshly mature leaves were collected and analyzed for nutrient content in the same laboratory. Nitrogen and sulfur present synergism in the growth and nutrition of the D. alata seedlings, with the doses of 100 mg dm -3 of N and 30 mg dm -3 of S being the most favorable to the higher development and quality of the seedlings. The interaction of P and B influences the contents and accumulation of these nutrients, indicating 300 mg dm -3 of P and 1 mg dm -3 of B. Fertilization with S interferes in the nutrition of the seedlings of the species for both the metabolism of N and impairing the absorption and accumulation of the macronutrients P, K and Ca and of the micronutrients B, Cu, Fe and Mn. The initial development of baru in the field, at 70 months, presents a low requirement of Ca and Mg after re-liming, improving the development of these plants, but not interfering with their nutrition. After 70 months, 40 g plant -1 of P₂O₅ provides further development of baru after reapplication of phosphate fertilization, promoting absorption of S.