Optimizing corn production and reducing nitrate losses with water table control subirrigation

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 N0(3)(-) losses. A greenhouse incubation study with three mater 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 NO3- loss through tile drainage (715 mu g 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, N2O production was increased by 12.7 times with the 30-cm WTC treatment (825 mu g 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 N2O 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.