Agronomic characteristics of two corn (Zea mays L.) varieties subjected to topdressing fertilization using different levels of nitrogen and potassium in Amazonas, Brazil

From the creation of new corn genomics to meet production demands, it is necessary to evaluate how these new cultivars react to the different environments that exist in Brazil. Front this, the objective of this study was to evaluate the effects of different levels of N and K used to topdressing fertilization on agronomic characteristics of two corn varieties at Amazon environmental conditions. The experimental design was randomized in block using a factorial scheme (2 x 4 x 4), with two corn varieties (BRS Caimbé and BR 5011 Sertanejo), four N dosages (0, 60, 100, and 140 kg.ha-1) and four K dosages (0, 20, 60, and 90 kg.ha-1). Each plot was constituted by five lines of 20 m of length and 2.40 m of width, with a space of 0.60 m among these, totalizing an area of 48 m2 per plot. Data collected were subjected to ANOVA and, subsequently, to Tukey test at 5% of significance. Caimbé corn variety presented higher (p < 0.05) number of plants, plant weight, and spikes per plot. High dosages of N and K provided high (p < 0.05) number of plants, plant weight, and spikes per plot. Caimbé corn variety presented higher (p < 0.05) spike weight and size. Other variables did not present significant (p > 0.05) results. High dosages of N provided high (p < 0.05) stem diameter and weight, leaf weight, spike size, and low spike weight. Lower levels of K caused low (p < 0.05) plant height, first spike height insertion, stem diameter, and spike weight.