Interactions in groups of experiments of fertilization of corn

The present paper has in view the study of linear interactions N'xP';N'x K' and P' x K' in four groups of 3³ factorial experiments of fertilization of corn, with N, P and K, involving 117 experiments and 3,159 plots. The groups were: Group 1: 53 experiments, carried out in Ribeirão Preto (SP), with the following levels of nutrients: 0; 40 and 80 kg/ha of N, P2 0(5) and K2 O. Group 2: 41 experiments, carried out in the State of Rio de Janeiro, with the levels: 0; 30 and 60 kg/ha of both N and K(2)0, and 0; 60 and 120 kg/ha of P2Os. Group 3: 10 experiments carried out in the Region of Triângulo Mineiro (MG) with the levels: 0; 75 and 150 kg/ha for the 3 nutrients. Group 4: 13 experiments carried out: 7 of them in Triângulo Mineiro, and the other 6 in Patos de Minas (MG), using the levels: 0; 60 and 120 kg/ha for each of the 3 nutrients. It was observed that only the interaction N'xP' using the levels 0 and 1 in group 1, and P' x K' using the levels 0 and 2 in group 2, were significant at the 5% level of probability. Then, it is possible to conclude, with a wide generality, that in 3³ factorial experiments of fertilization of corn, for moderate levels of nutrients, the interactions have little importance. In most of the cases, interactions are secondary when compared with the main effects of nutrients.