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Title: Do synergistic relationships between nitrogen and water influence the ability of corn to use nitrogen derived from fertilizer and soil?

Author
item Kim, Ki-In
item CLAY, DAVID - SD STATE UNIV.
item CARLSON, C - SD STATE UNIV.
item CLAY, SHARON - SD STATE UNIV.
item TROOIEN, T - SD STATE UNIV.

Submitted to: Agronomy Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/16/2008
Publication Date: 5/7/2008
Citation: Kim, K., Clay, D.E., Carlson, C.G., Clay, S.A., Trooien, T. 2008. Do synergistic relationships between nitrogen and water influence the ability of corn to use nitrogen derived from fertilizer and soil? Agronomy Journal. 100(3):551-556.

Interpretive Summary: Nitrogen (N) and water are important factors for increasing corn yield. Most available N sources for plants are N fertilizer and soil. The objective of the study was to determine the influence of soil water regime on the ability of corn (Zea mays L.) to utilize N derived from N fertilizer and soil. These results showed: 1) corn plants responded to N and water simulataneously; 2) N fertilizer increased water-use efficiency (170 kg vs 223 kg grain/cm in 0 and 112 kg N/ha treatments); and 3) water increased the ability of corn to utilize N derived from soil and N fertilizer. Yield goal based N recommendation models can be improved by replacing the constant with a variable by optimizing N use efficiency and yield as well as reducing the environmental impact of N. Therefore, producers will benefit from the improved N recommendation equations for site-specific N management. In addition, society will benefit from reduced N fertilizer use in precision farming.

Technical Abstract: To improve site-specific N recommendations a more complete understanding of the mechanisms responsible for synergistic relationships between N and water is needed. The objective of this research was to determine the influence of soil water regime on the ability of corn (Zea mays L.) to utilize N derived from fertilizer and soil. A randomized split-block experiment was conducted in 2002, 2003, and 2004. Soil at the site was a Brandt silty clay loam (fine-silty, mixed, superactive frigid Calcic Hapludoll). Blocks were split into moderate (natural rainfall) and high (natural + supplemental irrigation) water regimes. Nitrogen rates were 0, 56, 112, and 168 kg urea-N ha-1 that was surface applied. Water, soil N, and N fertilizer use efficiencies were determined. Plant utilization of soil N was determined by mass balance in the unfertilized control plots and by using the delta 15N approach in fertilized plots. Findings showed that: 1) plants responded to N and water simultaneously; 2) N fertilizer increased water-use efficiency (170 kg vs 223 kg grain cm-1 in 0 and 112 kg N ha-1 treatments, respectively); and 3) water increased the ability of corn to utilize N derived from soil (67.7 and 61.6% efficient in high and moderate water regimes, respectively, p=0.002) and fertilizer (48 and 44% efficient in high and moderate water regimes, respectively, p=0.10). Higher N-use efficiency in the high water regime was attributed to two interrelated factors. First, total growth and evapotranspiration (ET) were higher in the high than the moderate water regime. Second, N transport to the root increased with water transpired. For precision farming, results indicate that: 1) the amount of N fertilizer needed to produce a kg of grain is related to the yield loss due to water stress; and 2) the constant used in yield goal equations can be replaced with a variable.