To improve site-specific N recommendations a more complete understanding of the mechanisms responsible for synergistic relationships between N and water is needed. Th e objective of this research was to determine the influence of soil water regime on the ability of corn (Zea mays L.) to use 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 δ15N approach in fertilized plots. Findings showed that: (i) plants responded to N and water simultaneously; (ii) 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 (iii) water increased the ability of corn to use 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: (i) the amount of N fertilizer needed to produce a kg of grain is related to the yield loss due to water stress; and (ii) the rate constant used in yield goal equations can be replaced with a variable.
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American Society of Agronomy
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Kim, Ki-In; Clay, David E.; Carlson, C. G.; Clay, S. A.; and Trooien, T, "Do Synergistic Relationships between Nitrogen and Water Influence the Ability of Corn to Use Nitrogen Derived from Fertilizer and Soil?" (2008). Agronomy, Horticulture and Plant Science Faculty Publications. 141.