Exploring Nitrogen Limitation for Historical and Modern Soybean Genotypes

• Published in: Agronomy journal Vol. 110; no. 5; pp. 2080 - 2090
• Main Authors: Ortez, O. A., Salvagiotti, F., Enrico, J. M., Prasad, P. V. V., Armstrong, P., Ciampitti, I. A.
• Format: Journal Article
• Language: English
• Published: The American Society of Agronomy, Inc 01-09-2018
• ISSN: 0002-1962; 1435-0645
• DOI: 10.2134/agronj2018.04.0271

Yields (seed number) increased over time with modern soybean genotypes.
Seed protein concentration decreased over time.
Nitrogen fertilization impacted yield via changes on the seed weight.
Nitrogen limited yields for high‐yielding modern soybean genotypes.
The United States (USA) and Argentina (ARG) account for over 50% of the global soybean [Glycine max (L.) Merr.] production. Soybean N demand is partially met (50–60%) by the biological nitrogen fixation (BNF) process; however, an unanswered scientific knowledge gap exists on the ability of the BNF process to fulfill soybean N demand at varying yield levels. The overall objective of this study is to explore the potential N limitation using different N strategies for historical and modern soybean genotypes. Four field experiments were conducted during 2016 and 2017 growing seasons in Kansas (USA) and Santa Fe (ARG). Twenty‐one historical and modern soybean genotypes released from the 1980s to 2010s were tested under three N 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 growth stages (Full‐N). Historical soybean yield gains, from the 1980s to 2010s, were 29% in the USA and 21% in ARG. Following the yield trend, seed N content increased for modern genotypes in parallel to the reduction on seed protein concentration. Regarding N treatments, Full‐N produced 12% yield increase in the USA and 4% in ARG. Yield improvement was mainly related to increases in aboveground biomass, seed number (genotype effect), and to a lesser extent, to seed weight (N effect). This study suggests a potential N limitation for soybean, although there are still questions about the way in which N must be provided to the plant.