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Title: Nitrogen recovery and agronomic efficiency of forages with nitrogen fertilization under flooded condition

Author
item Sigua, Gilbert
item WILLIAMS, M. - Natural Resources Conservation Service (NRCS, USDA)
item Chase, Chadwick - Chad
item GRABOWSKI, J. - Natural Resources Conservation Service (NRCS, USDA)
item KONGCHUM, M. - Louisiana State University

Submitted to: Agricultural Sciences
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/25/2013
Publication Date: 5/20/2013
Citation: Sigua, G.C., Williams, M.M., Chase, C.C., Grabowski, J., Kongchum, M. 2013. Nitrogen recovery and agronomic efficiency of forages with nitrogen fertilization under flooded condition. Agricultural Sciences. 4(3):138-148.

Interpretive Summary: Public interest and awareness of the need for improving nutrient efficiency is great, but nutrient use efficiency can be defined in many ways, and could be easily misunderstood and misrepresented. Low soil fertility is one of the most important factors constraining forage productivity in subtropical United States especially in Gulf Coast states, as well as other parts of the world where cow-calf operation depends almost totally on grazed pastures. The use of inorganic source of nutrients (e.g., nitrogen fertilization) will continue to be indispensable for meeting global food, feed, and fiber needs. Particularly little is known about the response of forage species to the combined effect of waterlogging and the addition of nutrients (e.g., N and P). A two-year greenhouse study was conducted in 2008 and 2009 to determine i) the effect of flooding duration (0, 14, 28, 56, and 84 days) on nitrogen recovery and agronomic efficiency of bahiagrass compared with two flooding tolerant forages, limpograss and maidencane and ii) if nitrogen (N) fertilization (0, 100, and 200 kg N ha-1) could mitigate the negative effect of flooding. Agronomic efficiencies of bahiagrass (41 to 26%) and limpograss (44 to 31%) were reduced by flooding while agronomic efficiency of maidencane was increased from 24% (no flooding) to 46% at 84 d of continued flooding. However, nitrogen recovery and agronomic efficiency of three forage species was positively affected by nitrogen fertilization. The overall nitrogen recovery of bahiagrass, limpograss, and maidencane ranged from 44% to 59%. The practical implication of this study is that waterlogging may hamper nitrogen recovery and agronomic efficiencies while nitrogen fertilization could mitigate nitrogen recovery and agronomic efficiency of forage species under waterlogged condition.

Technical Abstract: The cow-calf (Bos taurus) industry in subtropical United States especially in Gulf Coast states and other parts of the world that depends almost totally on grazed pastures is facing several production constraints like changing climatic conditions and increasing cost of fertilizers, especially nitrogen. Particularly little is known about the response of forage species to the combined effect of waterlogging and the addition of nutrients. A two-year greenhouse study was conducted in 2008 and 2009 to determine (i) the effect of flooding duration (0, 14, 28, 56, and 84 d) on nitrogen recovery and agronomic efficiency of bahiagrass (Paspalum notatum Fluegge) compared with two flooding tolerant forages, limpograss (Hemarthria altissima Poir), and maidencane (Panicum hematomon Schult) and (ii) if nitrogen (N) fertilization (0, 100, and 200 kg N/ha) could mitigate the negative effect of flooding. Nitrogen recovery and agronomic efficiency varied significantly (P=0.001) among forage specie. Averaged across levels of N, nitrogen recovery of bahiagrass and limpograss was reduced by about 41% and 56%, respectively after 84 d of continued flooding while nitrogen recovery of maidencane was slightly increase by about 5% between 0 and 84 d of flooding. Agronomic efficiencies of bahiagrass (41 to 26%) and limpograss (44 to 31%) were reduced by flooding while agronomic efficiency of maidencane was increased from 24% (no flooding) to 46% at 84 d of continued flooding. The nitrogen recovery and agronomic efficiency of three forage species was positively affected by nitrogen fertilization. The overall nitrogen recovery of bahiagrass, limpograss, and maidencane ranged from 44% to 59%, therefore negative impact of waterlogging on nitrogen recovery and agronomic efficiency may have been mitigated by nitrogen fertilization.