Fontes e doses de nitrogênio e desenvolvimento inicial do mogno

Abstract

Mahogany is one of the largest commercial forest species whose value related to their nutritional requirement studies are scarce, especially regarding nitrogen (N) nutrient required by plants in larger amounts and complex dynamics in tropical soils and can be found either in the form as ammonium nitrate, logo, some plant species have a preference for one or another form. The present study aimed to evaluate the effect of forms and doses in the initial growth of mahogany. For experimental conduction was used pots containing 4.0 dm-3 Yellow Oxisol in a greenhouse. The experiment was arranged in a randomized block, factorial 2x6 +1 with five replicates. Treatments were two forms of N (nitrate and ammonium) and six doses (0, 50, 100, 150, 200, 400 mg.dm N-3) and an additional treatment (200 mg of 3-N.dm ½N- ½N and ammonium nitrate). At 150 days were evaluated height, stem diameter, leaf area, leaf dry weight, stem dry weight, dry weight of shoots, accumulation of nutrients in shoots, chloroplastidic accumulation of pigments (chlorophyll a, b and carotenoids) and index SPAD. There was an interaction between source and dose of N for accumulations of N, P and Mg; the accumulation of nutrients, growth and physiological parameters were little affected by the forms of N, however, the best results were observed with ammonium sulfate. In general the variables studied showed a quadratic fit to N except for stem diameter and accumulation of copper and iron in shoots treated with calcium nitrate. The development of mahogany is affected by N rates mainly in the form of ammonia being the best dose located around 263 and 254 mg.dm-3 N in the forms of calcium nitrate and ammonium sulfate, respectively.