Relative maturity group and its relationships with the non preferential sowing season of soybean

The cultivation of soybeans is the main agricultural commodity in Brazil, the increase in the cultivated area in recent years and the productivity of grains is interconnected with numerous factors such as sowing time, water availability, temperature and photoperiod. The objective of this work was to evaluate the duration of phenological sub-periods and the productivity of soybean cultivars from different groups of relative maturation, sown in two seasons in the off-season in the northwest region of the State of Rio Grande do Sul (RS). The experiment was carried out at Agropecuaria Bubans geographically located in the county of Ijui in the state of RS, considered medium locality. The experiment was carried out using a randomized block design with four replications, the experimental units consisted of four lines, four meters long, 0.50 m apart. The treatments were eight soybean cultivars with different groups of relative maturity (4.8, 5.8, 5.9, 6.2, 6.3, 6.4, 6.7 and 7.8) sown on January 5 and 22, 2019 (from agricultural zoning, the preferred season for sowing in this region is from october to december), constituting an 8 x 2 factorial experiment (Cultivars x sowing times). Assessments of the duration of phenological sub-periods and of the yield components of the culture were carried out, being measured with total plant height, first pod insertion height, number of lateral branches, number of reproductive nodes on the main stem, total number of nodes on the main stem, number of pods with one, two, three and four grains, pods mass of one, two, three and four grains, total grain mass per plant, thousand seed mass and grain yield. The most productive relative maturity group is 6.3 being sown in the first non-preferential season for soybeans in Rio Grande do Sul. The second sowing time changed the dynamics of association of the measured variables, with changes in the cycle, reductions in the vegetative and reproductive period.