Nitrogen (N) management in corn (Zea mays L.) production is a challenge for economic, agronomic and environmental reasons. Recovery of N by crops grown under most cropping systems is low. The inefficient use of N fertilizer represents approximately $680 million to $1 billion of direct economic losses annually for Canadian farmers alone. In humid environments such as northeast USA and eastern Canada, corn yield response to N amendments is poorly correlated with soil mineral N content before planting because of great spatial and temporal variability. Therefore it is important to develop new technologies for precision N management. In this chapter we have reviewed the major achievements in N dynamics in a soil-crop-atmosphere continuum, with emphasis on technologies developed for precision N management for sustainable corn production. Adoption of improved N management practices in corn production can increase both grain yield and N use efficiency (NUE) as well as minimizing N loading of the environment. Corn growth and development is driven by heat, which can be expressed as growing degree days or crop heat units. It takes about 6 weeks for a corn crop to reach quick growth stage. Excess N in the soil after preplant fertilizer application is subjected to leaching, run-off or emission losses, as N uptake during this part of the corn crop life cycle accounts for less than 15 % of plant total N. Up to date research indicates that it is of critical importance to understand the physiological mechanisms of crop NUE. This includes N uptake, translocation, remobilization and its relationship with grain yield which will maximize productivity and profitability as well as minimize N loading of the environment. An optimization between grain yield and NUE through precision N management is physiologically possible and practically achievable for sustainable corn production.

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