Plantios de Hymenaea courbaril L. em área alterada na região de Manaus: influência dos fatores de sítios do solo nos estoques de biomassa, nutrientes e na fotossíntese

Abstract

This research describes the influence of three fertilization types on a degraded area with Hymenaea courbaril plantation, a multiple purposes neotropical tree species. Changes in soil characteristics, tree aerial biomass and nutrient stocks, as well, ecophysiological parameters were investigated. The objectives of Chapter I were to determine morphological, physical and chemical soil characteristics (a very clayey, oligotrophic, Latossolo Amarelo / Oxissol) and the biomass of three plantations. Two plantations established in April 2001, had spacing 3 x 2 m, one received no fertilization (treatment SA) and the second received green manure (treatment AO). The third plantation (April 2002) with spacing 5 x 2 m received chemical fertilization (treatment AQ) in each planting hole (AQ; 150 g Fosmag®; NPK 15:5:10, + B e S). The fertilization was made at planting time and repeated the next four years with the same amount of fertilizer close to the trees. Green manure (AO) altered significantly soil chemical properties. In the superficial soil layers, the macro- and micronutrient content was higher than with chemical fertilization e.g. N: 2,48 g kg-1 (AO); 1,77 g kg-1 (AQ) and 1,36 g kg-1 (SA). In deeper layers (50 cm) of the soil profile the AO increased pH values (H2O e KCl) as carbon was reduced. H. courbaril trees were taller and biomass was twenty times greater with AO (273 Mg ha-1) than with SA (13 Mg ha-1) and AQ (34 Mg ha-1). In all treatments higher biomass was observed in trunks and fine branches (Ø < 10 cm) than trunks and thick branches (Ø > 10 cm). Chapter II objectives were to determine in H. courbaril the nutrients stocks in the tree compartments (leaves, fine branches, coarse branches and trunks) and investigate photosynthetic variables. All nutrient stocks were higher in trees with green fertilization e.g. P: 46,55 g/tree (AO) 13,97 g/tree (AQ) e 4,24 g/tree (SA). The thin branches (Ø < 10 cm), in trees of all treatments, were the compartment with the highest nutrient stocks. The trunk compartment had always less than 50 % of nutrient stock per tree. The green manure resulted in significant higher maximum photosynthesis (Amax) of H. courbaril (14,28 μmol CO2 m-2 s-1) compared to AQ (11,35 μmol CO2 m-2 s-1) and SA (9,58 μmol CO2 m-2 s-1). PSII photochemistry efficiency was also improved: Fv/Fm = 0,73 (AO) 0,69 (AQ) and 0,33 (SA). The H. courbaril plantation under influence of green fertilization was the most efficient to accumulate nutrients in the soil, as well as, higher biomass and nutrient stocks in the aerial compartments and a higher photosynthetic performance. In comparison to chemical fertilization, green manure had a higher impact on improved soil characteristics of degraded areas and biomass production of H. courbaril, probably because of the beneficial influence of C capture by photosynthesis and increase in photochemistry efficiency of PSII.