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ARS Home » Northeast Area » Beltsville, Maryland (BARC) » Beltsville Agricultural Research Center » Adaptive Cropping Systems Laboratory » Research » Publications at this Location » Publication #298034
Title: Strengths and limitations of nitrogen recommendations for corn and opportunities for improvements

Author
item MORRIS, THOMAS - University Of Connecticut
item KETTERINGS, QUIRINE - Cornell University
item SPARGO, JOHN - Pennsylvania State University
item Meisinger, John

Submitted to: Agronomy Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/30/2017
Publication Date: 1/4/2018
Citation: Morris, T.F., Ketterings, Q.M., Spargo, J.T., Meisinger, J.J. 2018. Strengths and limitations of nitrogen recommendations for corn and opportunities for improvements. Agronomy Journal. 110(1):1-37.

Interpretive Summary: Nitrogen plays a central role in crop production because it is essential for protein formation, it is an energy-intensive input, and it is the major limiting nutrient in agricultural soils. The goals of all nitrogen recommendation systems are to produce economic returns to the producer while maximizing recovery of all nitrogen inputs, and thereby minimizing losses to the environment. This requires managing nitrogen in harmony with the site-specific factors of soil nitrogen supply, crop needs, and nitrogen from other sources such as residual nitrate, legume residues, and animal manures. Various soil tests have contributed to improving nitrogen management systems. For example, measuring the concentration of soil organic matter can provide general estimates of nitrogen supplied from soil, while measuring pre-plant soil nitrate can assess the importance of residual nitrogen to the next crop. Other tests, such as the pre-sidedress soil nitrate test can identify nitrogen sufficient sites and improve fertilizer recommendations, while the corn-stalk nitrate test can provide an overall end-of-season assessment of the past year’s nitrogen management program. Other approaches such as in-field yield monitoring of strip-tests from a range of fertilizer nitrogen rates, including an unfertilized control, can provide direct yield response data to refine existing soil tests and to describe the spatial variability of the nitrogen response. While each of these tests has provided some success at the local or regional scale, a significant amount of uncertainty still remains in making corn nitrogen recommendations. These additional uncertainties are thought to involve closely linked soil-crop interactions that are affected by growing-season weather, with the plant not being a passive sink for nitrogen, but rather an avenue for transmitting weather effects into modifications of soil-crop nitrogen dynamics. This weather-soil-crop interaction has been named Biological Buffering Capacity, and developing further understanding of this interaction could improve current soil nitrogen tests and lead to new tests for improving corn nitrogen recommendations.

Technical Abstract: The goals of nitrogen (N) recommendation systems are to produce economic returns, maximize recovery of all N inputs, and minimize environmental losses. This requires managing N in harmony with the site-specific factors of soil N supply, crop N need, and N supplied from sources like residual nitrate-N (NO3-N), legume residues, and manures. Various soil tests have contributed to improving N management, such as soil organic matter or hydrolysable amino sugar tests for estimates of N mineralization, and pre-plant soil NO3-N tests for residual N. Other tests, like the pre-sidedress nitrate test can identify N-sufficient sites, while the corn stalk nitrate test provides an end-of-season assessment of the past year’s N management. Approaches such as yield monitoring of N-rate strip-tests, with a zero-N-control, can provide direct in-field N-response data to refine existing N tests and charactere N spatial variability. Each of these tests has provided some success at the local or regional scale, but significant uncertainty still remains. These uncertainties are thought to involve closely linked soil-crop interactions that are affected by growing-season weather, with the plant not being a passive N sink, but rather an active avenue for transmitting weather effects into modifications of soil-crop N dynamics. This weather-soil-crop interaction has been termed Biological Buffering Capacity (BBC). Many questions surround the concept of BBC, such as understanding the underlying processes, and how to best measure and manage BBC. However, additional knowledge about BBC can further improve current soil N tests and lead to improved corn N recommendations.