Is Controlled Drainage Worth The Extra Bucks, Time And Effort In Soybean Fields?

By Mohammad Shamim

The Midwest United States is one of the world’s leading soybean-producing regions. According to a 2017 Food and Agriculture Organization report, the region accounts for more than 34% of global soybean production. Over the years, soybean yields have increased steadily thanks to improved genetics and better management practices. While growers can influence genetics and management, weather remains largely out of our control.

Drought during critical reproductive growth stages can cause major yield losses, as many growers experienced this year. On the other hand, excessively wet springs can be just as damaging, leading to delayed planting, poor root development, and waterlogging. The good news is that yield losses from both dry and wet conditions can be reduced with proper water management—irrigation during drought and effective drainage during wet periods.

Although irrigation is often a costly investment and not feasible for all operations, drainage systems are one of the most effective and widely adopted tools for managing excess water. Good drainage improves soil health, allows timely field operations, and prevents prolonged waterlogging. Studies have shown that improved drainage can increase soybean yields by up to 8% (about 4 bu/acre) compared with poorly drained fields.

While surface drainage has been used for many years, subsurface drainage is increasingly recognized as a practical long-term solution. Growers considering subsurface drainage generally have two options: conventional (free-flow) drainage or controlled drainage. Controlled drainage systems use a water-level control structure to regulate how much water leaves the field. This allows producers to remove excess water during wet periods while retaining soil moisture during drier conditions. In addition to improving yield stability, controlled drainage has been shown to reduce nutrient losses and improve downstream water quality.

A multi-state study evaluating controlled drainage systems included 55 site-years across 13 field locations in the Midwest and North Carolina between 2000 and 2017. Overall, the researchers found no consistent yield advantage of controlled drainage compared with conventional (free-flow) drainage in corn production. However, weather conditions played a major role. During mild to moderate drought years, controlled drainage increased corn yield by 4–14% by helping conserve soil moisture. In contrast, during wetter growing seasons, yields were reduced by 4–10% due to excess soil water (Youssef et al., 2023).