Nitrogen response of two corn cultivars grown alone or intercropped in a soybean succession system in the Brazilian cerrado

The most widely used production systems in the Cerrado region are soybean (Glycine max)-corn (Zea mays) and soybean-corn intercropped with ruzigrass [Urochloa ruziziensis (Syn. Brachiaria ruziziensis)]. Thus, these systems may require a higher supply of mineral nitrogen (N) fertilizer. Therefore, the objective of this study was to evaluate the agronomic traits of two corn cultivars grow in the second-crop harvest in different environments, production systems, and N application rates in an Oxisol in the Cerrado region of Mato Grosso do Sul. The experimental design was a randomized block arranged in a split-split plot with three replicates. Plots consisted of two environments (UFMS 1 and UFMS 2), subplots consisted of two production systems [corn alone (monoculture) or corn intercropped with U. ruziziensis, and sub-subplots of five N application rates in topdressing (0, 40, 80, 120, or 160 kg N/ha). Urea was used as the source of N (45% N), and it was applied 30 days after emergence (DAE). Two corn cultivars (NS50 and Invictus Viptera 3) were used. During the flowering period of corn (i.e., after the emergence of female inflorescence), the relative chlorophyll index, leaf N concentration, plant height, and ear insertion height were recorded. At physiological maturity, the ear insertion height, ear length, number of grain rows per ear, number of grains per row, ear diameter, mass of one thousand grains, and grain yield were measured. The corn grain yield is lower in the system intercropped with U. ruziziensis when compared to the cultivation of corn alone (monoculture). In addition, the environment with greater soil base saturation and N availability (UFMS 2) results in a distinct response for the corn cultivar used; thus, a greater grain yield is expected from cultivar Viptera 3 in this environment. The maximum agronomic efficiency for corn grain yield is obtained with 102 to 123 kg N/ha for the Viptera 3 and NS50 PRO cultivars, respectively.