Omissão de macronutrientes em mudas de enxada-verde (Calopogonium mucunoides) em dois solos de terra firme da Amazônia Central

Abstract

The evolution of Amazonian soils is a combination of geological, geomorphological, vegetation and climate factors. The soils formed present limiting characteristics to intensive exploration and maximization of biological processes. The extreme poverty in available phosphorous, high acidity, high saturation by aluminium, low CEC, poverty in macro and micronutrients, susceptibility to erosion and leaching are the main conditioning factors for the expansion of agriculture in the region. The fertilizer species Calopogoium mucunoides has shown itself as a promising plant for its use in soils with extreme conditions, however, the knowledge about the use of nutrients for this legume is still incipient. Thus, this work aimed to evaluate the response to chemical fertilization with macronutrients, as well as the effects of its omission on development, symptoms of nutrient deficiency, nodulation and N2 fixation in seedlings of C. mucunoides, in two terra firme soils in central Amazonia. For this, an experiment was conducted at the National Institute for Amazonian Research (INPA), Campus V-8, in Manaus, with entirely randomized design (DIC), constituted by a factorial arrangement of the type 2 x 7, with seven repetitions, totaling 14 treatments and 98 experimental units. Factor A, soils, was considered for two classes of soils (Argissolo and Latosolo) and Factor B, fertilization with macronutrients, was considered for fertilization conditions: control, complete (N+P+K+Ca+Mg) = (C), (C) -N, (C) -P, (C) -K, (C) -Ca and (C) -Mg. The significance of the interaction soils x fertilization conditions was also considered. At 84 days after sowing, it was found that the species studied presents considered efficiency of N use, even though in the conditions of this study no formation of root nodules was observed. The macronutrients P and K were those that most limited the growth and biomass production of green hoe. The decrease in total dry biomass production of green hoe, presented the following order: -P > -K > -Ca > -Mg > -N. The observed symptomatology consisted only in reduction of plant growth and decrease of biomass gain.