Abstract
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 Agropecuária Bubans geographically located in the county of Ijuí 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.
Highlights
Soybean is one of the main crops of agriculture, with a relevant socioeconomic role, with Brazil being the second largest world producer of oilseeds
There was a significant effect for the interaction between sowing time x relative maturity group (T x relative maturity groups (RMG)) and significant effect for RMG alone, for all variables except for number of pods with four grains (NP4), pod mass with one grain (PM1), pod mass with four grains (PM4), number of pods on the lateral branch with four grains (NPLB4) and pod mass on the lateral branch with four grains (PMLB4)
For the isolated season effect, the variables that showed significance were the pod mass with one grain (PM1), total grain mass (TGM), thousand seed mass (TSM) and grain yield (GY) and for the treatment RMG alone, the variables that showed significance were the number of pods with 3 grains (NP3), pod mass with 4 grains (PM4) and grain yield (GY) (Table 2)
Summary
Soybean is one of the main crops of agriculture, with a relevant socioeconomic role, with Brazil being the second largest world producer of oilseeds. In the 2018/2019 harvest, the crop occupied an area of 35.8 million hectares in the country, with a 1.9% increase in planted area compared to the previous harvest, with an estimated production of 114.4 million tons of grains (Companhia Nacional de Abastecimento [CONAB], 2019; Hanyu, Costa, Cecon, & Matsuo, 2020; Soares, Sediyama, & Matsuo, 2020; Ferreira et al, 2020; Frota et al, 2020; Carvalho et al, 2021). Soybean is a short-day plant, influenced by the photoperiodic conditions characteristic of each latitude, especially with regard to the duration of the period of emergence to flowering, and, as the photoperiod decreases, the available solar radiation decreases (hours of light) (Ting-ting et al, 2015).
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