Value of cultural practices for improving nitrogen management in corn

Production and profitability of corn (Zea mays L.) is highly dependent on fertilizer nitrogen (N) use. The efficiency of fertilizer N use and the capacity of the soil to supply N are the two main components determining the corn N requirement. The cropping management system can also affect N use efficiency and soil N supply. A better understanding of the impact of management practices on corn N requirements is needed due to high N costs and increasing environmental scrutiny over fertilizer N use. The overall objective of this work was to characterize how cultural practices influence corn N requirements, and to develop strategies to adjust for any differences. The approach was to vary the N supply using different management practices over multiple sites and years. Practices evaluated included time of N application, degree of tillage, and varying levels of corn rootworm (Diabrotica spp.) larval damage. Results showed that management practices such as reduced tillage and/or fall or winter applied N can have a greater N requirement compared with more conventional production methods. The economic return to fertilizer N increased with increasing root injury and with decreasing tillage. Fall and winter N applications can cause large yield losses when compared to spring, however these losses can be predicted with spring rainfall and corrected with in-season N based on predicted loss. Management practices that increase the economic response to N, such as reduced tillage and increased root injury, have a greater likelihood of causing N stress and lower yield when other management practices, or environmental conditions decrease the availability of N.