Impact of water management by tile drainage on soybean yield and quality

Abstract

As climate change leads to more frequent extreme weather events, including intense rainfall and prolonged droughts, effective water management becomes critical for increased crop productivity. This study examined the role of subsurface drainage systems in mitigating water availability extremes, optimizing crop productivity, and enhancing nutrient use by managing excess water during heavy rainfall, improving soil aeration, and water retention during dry periods. The objectives of this research were to (i) evaluate the yield and quality impact of free drainage at 15 m spacing (FD-15), 8 m spacing (FD-8), and no drainage in sandy loam soils at Winkler, MB (ii) assess the yield impact of different subsurface water table depths (i.e., over-the-tile, midway-between-tile, and no-tile) in heavy clay soils at Arborg, MB, and (iii) simulate the yield impact of different water table depths (WTD) under soybean production using the DRAINMOD model in clay soils. In sandy loam soils, the yield from FD-15 plots was significantly higher (p < 0.05) than that from FD-8 plots, with narrowly spaced tiles over-draining the limited available water. The 2021 results indicated soybean yield was twice as high compared to 2020, despite both years receiving similar amounts of rainfall. This suggests that soybean yield is significantly influenced by the timing of rainfall during critical growth stages. The tile drainage research in heavy clay soils at Arborg, MB, during the 2020 and 2021 growing seasons, which were relatively dry years, showed a higher yield trend in tiled plots compared to the no-tile control plots. The higher yields in the tiled plots were due to the right amount of water being held back when needed and drained when in excess. Shallower water tables in the no-tile plots contributed to lower yields. In contrast, 2022, a wetter year, showed the over-the-tile treatment gave significantly higher yield (p < 0.05) compared to the no-tile treatment because the water was held back within the plot during critical stages in the over-the-tile treatments. Furthermore, the yield observed in the over-the-tile treatment exceeded the provincial average for the Interlake region. Although the total rainfall for 2020 and 2021 was the same, the soybean yield in 2021 was double that of 2020, indicating the timing of rainfall coinciding with critical growth stages led to higher yields. The 2020 data was used to calibrate and validate the DRAINMOD model to predict the water table depth in heavy clay soils at the Prairie East Sustainable Agriculture Initiative (PESAI) soybean plots. The calibrated DRAINMOD model was then used to predict the water table depth in 2021 and 2022, which statistically demonstrated strong agreement between measured and predicted water table depths. The validated DRAINMOD model was then used to predict relative yield for the different drainage treatments using weather data from 2012 to 2019. The predicted yield trends for the different drainage treatments showed a similar yield impact to what was observed from 2020 to 2022. The importance of water availability during critical growth stages (flowering, pod formation, and pod filling) on soybean yield is demonstrated. This research demonstrated the importance of managing the water table depth through controlled drainage to obtain higher soybean yield.