Exploring nitrogen limitation for historical and modern soybean genotypes

Authors: ORTEZ, O - KANSAS STATE UNIVERSITY; SALVAGIOTTE, F - NATIONAL INSTITUTE OF AGRICULTURAL TECHNOLOGY(INTA); ENRICO, J - NATIONAL INSTITUTE OF AGRICULTURAL TECHNOLOGY(INTA); PRASAD, P. V. - KANSAS STATE UNIVERSITY; Armstrong, Paul; CIAMPITTI, I - KANSAS STATE UNIVERSITY

Submitted to: Agronomy Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/11/2018
Publication Date: 8/9/2018
Citation: Ortez, O.A., Salvagiotte, F., Enrico, J.M., Prasad, P.V.V., Armstrong, P.R., Ciampitti, I.A. 2018. Exploring nitrogen limitation for historical and modern soybean genotypes. Agronomy Journal. 110(5):2080-2090. https://doi.org/10.2134/agronj2018.04.0271.
DOI: https://doi.org/10.2134/agronj2018.04.0271

Interpretive Summary: The United States and Argentina account for over 50% of global soybean production with soybean yield gains from the 1980s to 2010 of 29% for the USA and 21% for ARG. A little over 50% of soybean nitrogen (N) demand is met by biological N fixation (BNF) but it is unknown how well BNF satisfies soybean N demand at varying yield levels. This study examined the potential N limitation at different N application strategies for historical and modern soybean genotypes. Four field experiments were conducted during the 2016 and 2017 growing seasons in Kansas, USA and Santa Fe, Argentina using twenty-one historical and modern soybean genotypes released from the 1980s to 2010. These were tested under three N application rates. Results showed higher levels of applied N produced yield increases up to 12% in the US and 4% in ARG. Yield improvement was primarily related to increases in above-ground biomass, seed number, and to a lesser extent the individual seed weight. This study helps determine the potential N limitation for soybeans, although questions remain about the way in which N must be provided in-field.

Technical Abstract: The United States (US) and Argentina (ARG) account for over 50% of the global soybean [Glycine max (L.) Merr.] production. Soybean nitrogen (N) demand is partially (50-60%) met by the biological N fixation (BNF) process. An unanswered scientific knowledge gap is related to the ability of BNF to fully satisfy soybean N demand at varying yield levels. The overall objective is to explore the potential N limitation at varying N strategies, and for historical and modern soybean genotypes. Four field experiments were conducted during 2016 and 2017 growing seasons in Kansas (US) and Santa Fe (Argentina, ARG). Twenty-one historical and modern soybean genotypes with release decades ranging from 1980s and 2010s, all inoculated, were tested under three N management treatments: i) control without N application (Zero-N); ii) 56 kg N ha-1 applied at R3-R4 growth stages (Late-N); and iii) 670 kg ha-1 equally split at planting, R1, and R3-R4 stages (Full-N). Historical soybean yield gain, from 1980s to 2010s, represented 29% in US and 21% in ARG. Following the yield trend, seed N content was superior for modern genotypes relative to the oldest counterparts, in parallel to the reduction on seed protein concentration. Regarding N management, the Full-N produced up to 12% yield increase in US and 4% in ARG. Yield improvement was primarily related to increases in aboveground biomass, seed number (genotype effect), and in a lesser extent, to individual seed weight (N effect). This study portrayed a potential N limitation for soybeans, although there are still questions about the way in which this N must be provided to the plant.