Fertilização nitrogenada: produção, produtividade e trocas gasosas da soja cultivada em latossolo amarelo em casa de vegetação

Abstract

The earliest reports of domestication of the soybean crop (Glycine max (L.)) occurred in East Asia, in northeastern China. In Brazil, the crop presented a productive level in several regions, currently all the regions of Brazil present adequate conditions for the production of the soybean crop, the northern region has been showing great expansions, especially the municipality of Paragominas in the state of Pará. if it is a crop with great productive potential, nutritional need studies have become very necessary for decision making within a soybean crop. Among the essential elements required by plants, nitrogen is the one with the greatest effect on growth, responsible for root development. It is part of the chlorophyll molecule, constituent of amino acids, proteins, enzymes, coenzymes and nucleotides. However, because soybeans are a nitrogen-fixing legume, there are many discussions about complementing N for culture through mineral fertilizers. The objective of this work was to evaluate the effect of nitrogen on the soil associated with nitrogen via foliar in the components of production, productivity, gas exchange and concentration of nutrients in the leaves of the soybean cultivated in a clay latosol with a clay texture. The soil used to conduct the experiment was collected from the 0-20cm layer of the municipality of Paragominas-PA. The cultivar used was M8644. Five nitrogen doses were used, corresponding to 0, 25, 50, 75, 100 mg N dm-3, associated to foliar nitrogen fertilization. The following parameters were analyzed: number of pods per plant, number of grains per pod, number of grains per plant, weight of 100 grains and productivity, number of nodules per plant, photosynthesis, transpiration, stomatal conductance, intrinsic water use efficiency , instant water use efficiency, and concentration of macro and micronutrients in the leaves. The analyzed variables presented satisfactory results. It is possible to conclude that the combination between the dose of 25mg dm-3 of nitrogen and the application of N via leaf had a significant influence on the production and productivity variables analyzed, for the gas exchange variables, the best results are related to the dose of 50 mg dm-3. In this way, the application of nitrogen through soil associated with nitrogen via foliar in the soybean plants becomes viable.