Evaluating the impact of subsurface drainage and subirrigation on wheat production in heavy clay soils
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Effective water management is crucial for optimizing crop productivity. This study investigated the effectiveness of subsurface drainage and subirrigation in managing soil water for wheat production in heavy clay soils at Arborg, Manitoba. Field experiments were conducted at the Prairie East Sustainable Agriculture Initiative (PESAI) farm at Arborg, Manitoba. Different subsurface drainage designs (30-ft (9.1 m) and 45-ft (13.7 m) spacing) were used for subirrigation during the 2022 and 2023 growing seasons. Soil moisture response under these systems was assessed at 0.2, 0.6, and 0.9 m depths using soil moisture sensors for continuous monitoring throughout the growing season. In 2022, with above-average rainfall, controlled drainage removed adequate amount of water and resulted in significantly higher yield (p < 0.05) midway-between-tiles in the 30-ft spacing plot compared to the non-tiled control. In contrast, during the dry year of 2023, despite subirrigation, yield from the 30-ft plot was lower than the average yield in the Interlake region due to insufficient water. However, the on-tile treatment in the 45-ft plot and control (non-tile) plot produced significantly (p < 0.05) above-average yields in 2023 due to less water being drained from the field compared to the 30-ft plot. The data from this research was used to calibrate and validate the DRAINMOD model to assess the influence of tile drain spacing and subirrigation on relative yield in 2021, 2022 and 2023. Simulation results indicated that in 2022, relative yields in the 30-ft and 45-ft plots were 97.2% and 97.0%, respectively. Subirrigation reduced drought stress in the 15-ft plot during 2021, a dry year. A six-day planting delay caused a 5.2% yield loss in 2023. These findings demonstrated the importance of optimally managing controlled drainage systems to enhance wheat yield in heavy clay soils.