Improved water management of a poorly drained floodplain soil and the impact on forage production and nitrate concentration

Abstract

As livestock demand and production continue to rise in the United States, there is a greater need for increased forage production and improved forage quality. Forage production will need to expand to soils with production restrictions, such as poorly drained floodplain soils, in order to meet future demands. The objectives of the study were to evaluate the impact of free drainage (FD), managed drainage systems (MD), and no drainage (ND) on forage production, nitrogen (N) uptake, and nitrate (NO₃) concentration in rye (Secale cereale L.) and forage sorghum (Sorghum bicolor [L.] Moench). On average across years, MD did not increase forage production compared to FD, but the presence of subsurface drainage (both FD and MD) increased total forage biomass production by 27% to 32% compared to ND. Annual plant N uptake increased 30% with MD and 41% with FD compared to ND when averaged across the four-year study. Nitrate concentration in rye mass never reached a concentration that could impact cattle grazing the forage over the four-year study. Regardless of subsurface drainage system, NO₃ concentration in forage sorghum in two study years ranged from 1,310 to 4,520 mg kg⁻¹, which corresponded to toxic to extremely toxic levels. Dry summer months may have contributed to the high NO₃ concentrations observed in forage sorghum. Subsurface drainage may provide farmers with an opportunity to increase annual forage production from rye and forage sorghum, but farmers should have forage sorghum tested for NO₃ concentrations before feeding.