Long-term drainage water recycling affects soil health and soil properties

Drainage water recycling (DWR) using drainage and subirrigation (DSI) has increased the resiliency of crop production and improved water quality in the midwestern United States, but the effects on soil properties and soil health parameters have not been determined. This research evaluated (1) reservoir nutrient concentrations of a long-term DWR site over time, (2) the effects of a DWR system on soil properties at four depths in a corn (Zea mays)–soybean (Glycine max L.) rotation compared to free drainage (FD) and nondrained (ND) soil, and (3) the influence of DWR on soil health parameters after a 17-year corn–soybean rotation compared to ND. Different laboratory methods for estimating these soil health parameters were compared. In the initial years of the study (2002 to 2007), concentration of salts (potassium [K] and sodium [Na]) and dissolved nutrients (nitrogen [N] and phosphorus [P]) were higher in the reservoir water. Mean concentrations were 1.8 mg L−1 for nitrate-N (NO3-N) and 0.36 mg L−1 for orthophosphate (PO4-P) in the reservoir during the study. The concentration of salts and ions in the reservoir were not restrictive for use as irrigation water for plants. The DWR treatment had a soil texture that was 11% lower in silt (P < 0.001) and 13% higher in clay (P < 0.001) concentration at 21 to 30 cm soil depth compared to ND. The water table fluctuations appeared to influence cation (calcium [Ca], magnesium [Mg], and K) movement in soils while the FD and DWR treatments had lower soil test P in the topsoil. No significant interaction in soil analysis methods × treatments were observed (P > 0.1), indicating the absence of an effect of analysis methods (Haney soil test, Soil Health Management Assessment Framework, and Cornell Soil Health Assessment) on assessment of soil properties. DWR did not alter soil properties or soil health parameters.