This paper reports the results of 32 yield trials carried out in different localities, covering - Massapê, Terra Roxa, Arenito Bauru, Glacial and Terciário - great types of soils in the State of São Panlo. The experimental design was a 3³ with the following treatments: three varieties - Cateto, Asteca and H. 6999; three populations 50, 33 and 25 thousand plants per hectare; and three fertilizer levels - 0, 1 and 2. Dosis 1 corresponds to 25-68-22.5 kg/ha of NPK. Each plot was 30 m². Statistical analyses of each trial and also of the groups of experiments were made to test main effectB and interactions. According to the adopted model, Y = m + v + a + e + va + ve + ae + l+ lv-f-la + le + lev + lva + lea + b (1) + E. m was the general average, v, a, e, and l, i, e, variety, fertilization, spacing, location and their interactions; b(1), replication effect within localities and E the residual error including some high order interactions. Linear and quadratic components for a and e were orthogonally decomposed; V1 being Cateto against H. 6999 + Asteca and v2 being H. 6999 against Asteca. The average variation coefficient was 15 per cent; only in 4 of the 32 trials was the variation coefficient larger than 20 per cent. On the average the double cross hybrid H. 6999 outyielded significantly the variety Asteea by 572 kg/ha. Asteca + H. 6999 were 834 kg/ha better than Cateto. An increase of 843 kg/ha was obtained with a population of 50,000 plants over the treatment which corresponds to 25,000 plants per hectare. The average response to fertilisation did not differ for the great types of soils. A significant linear effect of 1,300 kg/ha measured from level 0 to level 2 was recorded; also a quadratic significant response was verified, indicating that the maximum whould be obtained with 50-150-50 kg/ha of NPK. The data obtained in this group of trials indicated that the highest average yield 5,395 kg/ha was attained with the hybrid H. 6999 that received the high level of fertilizers rated to a 50,000 plant population. For this treatment 1.07 ears per plant were recorded. The average weight per ear was 151 g.