By Andi Anderson
Soybeans require a different irrigation approach than corn because of their unique growth habit. Unlike corn’s “determinant” growth pattern, soybeans are “indeterminate,” meaning they continue vegetative growth after flowering. This affects nutrient uptake and explains why soybeans often show less response to traditional corn-style irrigation.
Total seasonal water use for soybeans averages 18 to 20 inches, slightly less than corn. Early irrigation is usually unnecessary. Before the R3 stage, excess watering can cause taller plants with shallow roots, increasing the risk of lodging. Soybeans tolerate early drought better than corn, so light applications—about half to two-thirds of corn’s rate—are enough if conditions are very dry. During flowering and pod development (R1–R6), water demand peaks, matching corn levels. Maintain at least 50 percent soil water capacity until most pods have yellowed to secure final yield.
Efficient scheduling methods help conserve water. Evapotranspiration (ET) scheduling uses reference ET data and crop coefficients to estimate daily plant water loss. Soil moisture sensors measure volumetric water content or soil tension to guide irrigation. Trigger watering when 40–50 percent of available water is depleted mid-season and 60–70 percent late in the season. Correct sensor placement across the root zone ensures accurate readings and avoids over- or under-watering.
Disease management is vital for irrigated soybeans. White mold thrives in moist conditions. Select resistant varieties, reduce seeding rates, and delay heavy irrigation until the full pod stage (R4). Apply effective fungicides between the beginning of flowering and early pod growth (R1–R3) for best protection.
Finally, remember that irrigation can increase biomass without increasing yield. Monitor nutrients such as nitrogen and sulfur, especially in low-organic-matter soils, to match higher moisture and growth. By combining precise scheduling, careful disease control, and proper nutrient management, farmers can use water wisely and maximize soybean yield potential.
Photo Credit: gettyimages-songbird839
Categories: Michigan, Crops, Corn, Soybeans