Residual soil nitrogen credits for corn production along the upper Texas Gulf Coast region

ABSTRACT

Studies were conducted to evaluate response of dryland corn (Zea mays L.) along the upper Texas Gulf Coast to residual soil nitrate-nitrogen (NO₃-N) measured to depths of 15, 30, and 61 cm. Residual soil NO₃-N levels ranged from 3.4 to 31.6, 7.8 to 49.3, and 9.0 to 71.7 kg ha⁻¹, respectively, in 0 to 15, 15 to 30, and 30 to 61 cm depth increments, with cumulative NO₃-N ranging from 23.5 to 114.5 kg ha⁻¹ across sites-years. Where N fertilizer was reduced due to N crediting, yields and bushel weights at all 13 site-years showed no difference from those receiving full recommended N rates. A yield response to any level of added fertilizer N above the control was observed for only 6 of 13 site-years. These results indicate a high potential for success in crediting carryover soil NO₃-N to 61 cm as a means of reducing applied nitrogen fertilizer rates.

KEYWORDS:

• Corn
• nitrate
• residual nitrogen
• soil profile
• soil testing
• yield goal

Acknowledgements

The authors wish to thank J. R. Simplot Company and Crop Production Services for donating fertilizers. Appreciation is extended to Dr. Amir Ibrahim for assistance with data analysis. Special thanks also to season-long efforts made by grower-cooperators, AgriLife County Extension and Integrated Pest Management Agents, Dennis Pietsch, Russell Sutton, Dale Mott, Archie Abrameit, and Al Nelson.