Submitted to: Agronomy Journal
Publication Type: Peer reviewed journal
Publication Acceptance Date: 8/15/2005
Publication Date: 3/15/2006
Citation: Seo, J., Meisinger, J.J., Lee, H. 2006. Fate and recovery of nitrogen-15 labeled hairy vetch and fertilizer applied to corn. Agronomy Journal. 98:245-254. Interpretive Summary: Understanding the fate of nitrogen from legume cover-crop residues and from fertilizer is essential for developing corn nitrogen management practices that efficiently utilize both of these sources. Labeled ammonium sulfate fertilizer or labeled hairy vetch residues were applied to corn at planting, or at the 6-leaf stage (sidedressing), and the fate of the labeled nitrogen was followed into the silage corn and into the surface six inches of loam textured soil. The study was conducted in Suwon Korea and used 15 inch diameter by 24 inch deep cylinders to define the corn root- zone and to provide for accurate soil sampling after the harvest of the silage corn. The silage corn took up 32% of the planting-applied fertilizer, 15% of planting-applied hairy vetch residues, and 46% of the fertilizer applied at sidedressing. Conversely, hairy vetch residues contributed more nitrogen to the soil (38%) compared to planting applied fertilizer (15%) or sidedress fertilizer (14%). The total recoveries of labeled N in crop plus soil were 47% for planting applied fertilizer, 54% for hairy vetch residues, and 60% for sidedressed fertilizer. The availability of the residual labeled N to corn grown on the same plots the following year was small. These results are consistent with other studies comparing labeled legume residues with fertilizer, and show that fertilizer is about twice as effective as legume residues in supplying nitrogen to a crop, while legume residues contribute about twice as much nitrogen to the soil. This study is of interest to crop advisors, CSREES extension specialists, and NRCS soil scientists because it demonstrates that a nitrogen management system utilizing both legume cover-crop residues and fertilizer can meet both crop and soil nitrogen needs, and thus contribute to more sustainable agricultural system.
Technical Abstract: Knowledge of the fate of N from legume cover-crop residues and fertilizer is needed to develop corn nitrogen (N) management systems that efficiently utilize both of these N sources. Nitrogen-15 labeled ammonium sulfate (AS) or hairy vetch (Vicia villosa Roth.) residues were applied at planting or at the 6-leaf stage (sidedressing) to silage corn (Zea mays L.) grown in 38 cm diameter by 60 cm deep microplots containing a Jungdong loam (coarse loamy, mixed, mesic, Typic Udifluvents) in Suwon, Korea. The fate of the labeled N sources was traced into the corn grain, stover, and the soil. A second year of study documented residual N effects. Corn took up 32% of the planting-applied AS, 15% of planting-applied hairy vetch (HV) residues, and 46% of the sidedress AS. Conversely, HV residues contributed more N to the soil N pool (38%) compared to planting AS (15%) or sidedress AS (14%). Total recoveries of labeled N in crop plus soil were 47% for planting AS, 54% for HV residues, and 60% for sidedress AS. Availability of residual labeled N to the second-year corn was small. These results are consistent with other studies comparing labeled legume residues with AS, and show that AS is about twice as effective as legume residues in supplying N to a crop, while legume residues contribute about twice as much N to the soil. This study demonstrates that a N management system utilizing both legume cover-crop residues and fertilizer N can meet both crop and soil N needs, and contribute to more sustainable N management systems.