Optimizing Corn Production and Reducing Nitrate Losses with Water Table Control‐Subirrigation

Abstract Water table control‐subiriggation (WTC) systems have increased crop production and improved water quality; however, the relationship between N management, water table depths, and corn production has not been well defined. We hypothesized that optimizing water table depth would increase corn ( Zea mays L.) growth, improve N fertilizer efficiency, and reduce NO ‐ 3 losses. A greenhouse incubation study with three water table depths (30, 60, and 80 cm) and four N rates (0, 0.7, 1.4, and 2.1 g N plant ‐1 ) was conducted using undisturbed soil columns (Fox sandy loam, Typic Hapludalf) planted to corn. The 30‐cm WTC treatment had the greatest NO ‐ 3 loss through tile drainage (715 µg N column ‐1 ). The 60‐cm WTC treatment reduced these losses by 54%. Nitrate losses through tile drainage were proportional to drainage volume, which followed the order 30 cm > 60 cm > 80 cm WTC. The 60‐cm WTC treatment increased crop yields (95 g plant ‐1 ) compared with the 30‐cm (68 g plant ‐1 ) and 80‐cm WTC (18 g plant ‐1 ) treatments at the optimal N rate of 1.4 g N plant ‐1 . After the first simulated rainfall event, N 2 O production was increased by 12.7 times with the 30‐cm WTC treatment (825 µg N column ‐1 d ‐1 ) compared with the 60‐ and 80‐cm WTC treatments. Water stress imposed by the 80‐cm WTC treatment limited crop growth, N uptake, leaching, and N 2 O emissions. However, up to 28% of added N (664 mg N column ‐1 ) remained in the soil after corn was harvested from the 80‐cm WTC treatment, which would be susceptible to leaching between cropping seasons.