Drainage water management impacts soil properties in floodplain soils in the midwestern, USA

Subsurface drainage is one of the most commonly used water table management practices in the Midwest U.S. Subirrigation through the subsurface drainage system using drainage water recycling (DWR) was developed to meet crop production goals and address environmental concerns. The objective of this study was to examine differences in soil properties after seven-years of subsurface drainage treatments [no drainage (ND), drainage only (DO), and drainage plus subirrigation (DWR)] in continuous corn production in Knox County, Missouri. Soil samples were collected at 0-10, 11-20, 21-40, and 41-60 cm depths periodically from 2015 to 2021 and were analyzed for soil pH, cations, cation exchange capacity (CEC), nitrate-N (NO3-N), phosphorus (P), organic matter (OM), total carbon (TC), bulk density (BD), penetration resistance, and soil texture. A significant shift in soil texture from 2015 to 2021 was observed with a 26% and 11% increase in the clay content at a 41-60 cm soil depth in DWR and DO treatments, respectively, compared to ND. Accelerated soil OM and TC mineralization was observed with DWR which may be due to soil acidification, increased soil moisture, and aeration compared to DO and ND. This was further supported by increased CEC at deeper soil depths. In addition, increased reservoir water pH and electrical conductivity in 2016 and 2017 may have amplified the water table fluctuation effects on soil properties. The mean concentration of sodium (Na), potassium (K), bicarbonate, sulfate, nitrate, and phosphate were in an acceptable range for use as irrigation water. In conclusion, continuous corn production under DWR affected soil texture and enhanced soil acidification, which in turn amplified the mineralization of soil OM and TC.