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The 2025/2026 soybean crop is expected to face a planting start marked by significant climatic challenges. According to analyses by AtmosMarine, the conditions predicted for November and December indicate irregular rainfall, above-average temperatures, and direct impacts on the initial development of the crops, decisive factors for the final productivity of the oilseed.
Photo: Jose Fernando Ogura
The total water demand of soybeans, which varies between 450 mm and 800 mm throughout the cycle, needs to be adequately distributed between the vegetative and reproductive phases. When this does not occur, the effect is directly seen in the yield. The 2023/2024 crop is a recent example: delays in the regularization of rainfall in the Central-West and Matopiba regions, prolonged droughts, and excessive precipitation in the South caused significant reductions in crop performance.
The grain-filling stage, one of the most sensitive to water and heat stress, is a cause for concern. Water deficits reduce grain size and compromise final weight, while extreme temperatures (below 10°C or above 40°C) impact flowering, pod formation, and reproductive structure. "When the average temperature exceeds the ideal range of 20°C to 30°C, soybeans enter a level of stress that can reduce productivity even during short periods of intense heat," explains meteorologist Gabryele de Carvalho.
In addition to water and temperature, soybeans also respond to photoperiod. As a short-day plant, its flowering is induced by a reduction in daily light hours, a factor that determines the adaptation of each cultivar to the different regions of Brazil.
Producing regions and forecasts
The country's main producing regions, Mato Grosso, Goiás, Mato Grosso do Sul, Paraná, Rio Grande do Sul and the Matopiba area, will have
Photos: Disclosure/OPR Archive
Distinct scenarios are expected throughout November and December. In Mato Grosso, the forecast indicates irregular rainfall in November, with above-average volumes in the north and below-average volumes in the south, while December should present higher-than-expected rainfall. Temperatures remain high in both months, with an average of 29°C. In Goiás, the end of November and the month of December should register above-average rainfall, accompanied by equally high temperatures.
Meanwhile, Mato Grosso do Sul will experience irregular rainfall patterns in November, with above-average rainfall in the east and below-average rainfall in the west, but December should bring higher accumulations across the state, with average temperatures close to 28°C. In the south of the country, Paraná and Rio Grande do Sul are expected to face a drier period, with below-average rainfall in both November and December, as well as above-normal temperatures, reaching averages close to 21°C.
The La Niña pattern is expected to persist into December, but at a weak intensity, which reduces the likelihood of significant impacts on rainfall patterns.
The harvest will require extra attention.
The combination of variables (irregular rainfall, high temperatures, and the need for adjustments to the planting calendar) reinforces the importance of continuously monitoring weather updates. "Producers need to be attentive to weather patterns over the coming weeks, as small changes at the beginning of the cycle can have a significant impact on final yield," points out the meteorologist.
