Nitrogen partitioning and utilization in corn cropping systems: Rotation, N source, and N timing

Nitrogen partitioning and utilization can partly control plant productivity. This study was conducted to estimate dry matter (DM) and N partitioning parameters in corn (Zea mays L) as affected by N source, N timing, and crop rotation. We quantified yield by combine, aboveground DM accumulation [residues (stalk + cob) and grain], and C and N concentrations at growth stage R6 of corn continuously cropped (CC) or in rotation with soybean [Glycine max (L) Mem] (CS) and fertilized with side-dressed urea-ammonium nitrate (UAN) or with liquid swine manure applied in either spring (SM) or fall (FM). Of the assessed N partitioning parameters. N utilization showed the highest association with yield (r = 0.94***). Across treatment means, 72% of these increases in N utilization could be attributed to increases in N uptake. On the contrary, N harvest index (NHI) exhibited nearly constant values across experimental units, and therefore. NHI showed a minor relative contribution to variations in N utilization, thus supporting the basic premise of low NHI dependency on environment or management. Both N uptake and N utilization were driven by type of N addition (UAN > manure). Also, corn N utilization and yield were greater (10-13%) within the corn-soybean rotation, suggesting that a shift in land use from crop rotations into more continuous corn due to increasing demand for corn grain may impose additional challenges for enhancing plant N nutrition and sustaining yield. (C) 2011 Elsevier B.V. All rights reserved.