Effect of Flooding Duration and Nitrogen Fertilization on Yield and Protein Content of Three Forage Species

Increasing the availability and improving the quality of surface water in south Florida by temporarily flooding previously drained pastureland is one of the goals of Northern Everglades Restoration Initiative. Bahiagrass (Paspalum notatum Fluegge) is one of the most important forage grasses in the region and although tolerant to short-term flooding, bahiagrass is classified as a facultative upland (FACU+) species that suggest dry matter production and plant persistence might be reduced under periods of extended waterlogging. A 2-yr greenhouse study was conducted in 2008 and 2009 to determine the effect of flooding duration on dry matter yield (DMY) and crude protein content (CPC) of bahiagrass compared to two flooding tolerant forages, limpograss (Hemarthria altissima Poir), and maidencane (Panicum hematomon Schult) and to determine if N fertilization could be used to mitigate flooding effects. Dry matter production and CPC levels varied with flooding durations (P <= 0.001) and levels of N fertilization (P <= 0.001). Averaged across flooding duration and levels of N, limpograss had the greatest dry matter yield of 11.6 t ha(-1) followed by maidencane (8.6 t ha(-1)) and bahiagrass (8.5 t ha(-1)) while bahiagrass had the highest CPC of 6.9% followed by maidencane (6.0%) and limpograss (3.7%). The overall yield response of the three forage species: bahiagrass (R-2 = limpograss (R-2 = 0.93**); and maidencane (R-2 = 0.99**) were linearly related to increasing levels of N fertilization. Crude protein contents of three forage species: bahiagrass (R-2 = 0.97**), limpograss (R-2 = 0.99**), and maidencane (R2 = 0.87** were also linearly related to increasing levels of N fertilization. Averaged across forage species, dry matter yield of forages fertilized with 200 kg N ha(-1) with no flooding were statistically comparable with plants that were fertilized with 200 kg N ha(-1) and flooded for 84 d. Our results support our hypothesis that the negative impact of flooding could be mitigated by N fertilization.