Potencial de rendimiento de soja en distintos ambientes agrícolas del este de Uruguay

Soybean is the main agricultural crop in Uruguay, and its expansion into the eastern region has increased the need to better understand the productive potential of these environments. In this region, soybean production is mostly carried out under rainfed conditions and on soils with limitations related to water availability, drainage, and interannual climate variability. In this context, crop simulation models are useful tools to estimate potential yields and analyze crop responses to different combinations of soil, climate, and management. The objective of this study was to estimate the potential yield (Yp) and water-limited potential yield (Yw) of medium maturity group VI soybean in different agricultural environments of eastern Uruguay, integrating edaphic and climatic variability through the use of the Cycles simulation model. Five representative locations were evaluated: Melo, Rincón de Ramírez, Río Branco, Treinta y Tres, and Velázquez. For each location, a representative soil unit, two water conditions -irrigated and rainfed- and six sowing dates, ranging from mid-October to late December, were considered. Simulations covered 64 growing seasons, and the results were analyzed in terms of mean yield, interannual variability, climate condition, sowing date, differences between irrigated and rainfed conditions, and ranking stability among locations. The regional average potential yield was 4.53 Mg ha⁻¹, while the water-limited potential yield reached 3.61 Mg ha⁻¹. Río Branco showed the highest yields under both irrigated and rainfed conditions, whereas Melo recorded the lowest values. Irrigation increased mean yield and reduced interannual variability, with an average difference of 0.92 Mg ha⁻¹ between irrigated and rainfed conditions. This difference was larger in dry years and smaller in wet years, indicating that the contribution of irrigation increases as water availability becomes more restrictive. Sowing date had a marked influence on yield. Early sowing dates maximized both Yp and Yw, while progressive delays in sowing reduced yield under both water conditions. Under rainfed conditions, late sowing dates showed lower relative variability, but also lower yields in the lower quartile of the distribution. In addition, the rainfed yield ranking analysis showed high temporal consistency among locations, with Río Branco occupying the first position in most growing seasons and Melo frequently ranking last. The results indicate that early sowing dates represent the most favorable strategy to maximize the yield of medium maturity group VI soybean in the evaluated environments. However, the magnitude of the response depends on water condition, location, and interannual climate variability. The use of irrigation is especially relevant in environments that are more sensitive to water restrictions, as it increases expected yield and reduces production instability. These results provide useful information to support management decisions and contribute to the design of agricultural systems better adapted to the conditions of eastern Uruguay.