Nitrogen credits after peanut (Arachis hypogaea L.)

Authors: MULVANEY, MICHAEL - Mississippi State University; IBOYI, JOESEPH - University Of Florida; Balkcom, Kipling; JORDAN, DAVID - North Carolina State University; ZURWELLER, BRENDAN - Mississippi State University; JANI, ARUN - California State University

Submitted to: Agronomy Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/31/2024
Publication Date: 9/2/2024
Citation: Mulvaney, M.J., Iboyi, J.E., Balkcom, K.S., Jordan, D., Zurweller, B., Jani, A. 2024. Nitrogen credits after peanut (Arachis hypogaea L.). Agronomy Journal. 116:3344-3353. https://doi.org/10.1002/agj2.21669.
DOI: https://doi.org/10.1002/agj2.21669

Interpretive Summary: Throughout the peanut growing region of the US, Cooperative Extension Service soil fertility recommendations recommend a 22-67 kg N/ha credit to crops following peanut, due to the assumption that peanut, being a legume, contributes N to the following crop. However, cooperators from Univ. of Florida and an ARS scientist in Auburn, AL examined the peer-reviewed literature and found N credits from peanut to the next crop are negligible. Recent literature suggests yield differences following peanut compared to non-legumes results from non-legume crop residue favoring N immobilization, while peanut residue favors N mineralization. Recent research and peer-reviewed literature do not support Cooperative Extension Service recommendations to reduce N fertilization after peanut. Finding N loss pathways after peanut harvest will mitigate N losses and improve management strategies. Applying N credits appropriately to N recommendations ensures that N under-fertilization of the following crop does not occur, which can significantly reduce grower yields and profits.

Technical Abstract: State-level Cooperative Extension Services provide fertilizer recommendations for row crops in the United States (U.S). Of these, nitrogen (N) recommendations are arguably the most important because N is the most common yield-limiting nutrient in non-legume crop production systems. Throughout the peanut (Arachis hypogaea L.) growing region of the US, Cooperative Extension Services generally recommends 22-67 kg N/ha credit to crops following peanut, likely due to the assumption that peanut, being a legume, contributes N to the following crop. The body of peer-reviewed literature indicates that N credits from peanut to the subsequent crop are negligible. Recent literature indicates that apparent differences in yield following peanut compared to a non-legume are a result of non-legume crop residue favoring N immobilization rather than N mineralization from peanut residue. Taken together, recent research corroborates the few previous scientific publications addressing the issue, namely that Cooperative Extension Service recommendations to reduce N fertilization to crops after peanut are not supported by the peer-reviewed literature. Future field research should include summer fallows to determine if yield differences after legumes and non-legumes are due to N credits by the legume or N immobilization by non-legumes. Data on N loss pathways following peanut are needed to identify management strategies that can mitigate N losses after peanut harvest. In conclusion, the preponderance of peer-reviewed science does not support current Extension recommendations regarding peanut N credits to the following crop.