Insufficient nitrogen supply from symbiotic fixation reduces seasonal crop growth and nitrogen mobilization to seed in highly productive soybean crops

• Published in: Plant, cell and environment Vol. 43; no. 8; pp. 1958 - 1972
• Main Authors: Cafaro La Menza, Nicolas, Monzon, Juan Pablo, Lindquist, John L., Arkebauer, Timothy J., Knops, Johannes M. H., Unkovich, Murray, Specht, James E., Grassini, Patricio
• Format: Journal Article
• Language: English
• Published: Chichester, UK John Wiley & Sons, Ltd 01.08.2020; Wiley Subscription Services, Inc
• Subjects: Accumulation; Agricultural production; Crop growth; Crop yield; Crops; Crops, Agricultural - growth & development; Crops, Agricultural - physiology; Dry matter; Environmental management; Fertilizers; Glycine max (L.) Merr; Glycine max - growth & development; Glycine max - physiology; Leaf area; Leaf area index; Nebraska; Nitrogen; Nitrogen - metabolism; Nitrogen Fixation - physiology; Nitrogenation; Organs; Original; Plant growth; Plant Leaves - physiology; Radiation; Seasonal variations; Seasons; Seed set; Seeds; Seeds - growth & development; Seeds - metabolism; Soil fertility; Soil treatment; Soils; soybean; Soybeans; Symbiosis; symbiotic fixation; Nebraska; soybean; Glycine max (L.) Merr; nitrogen; leaf area; symbiotic fixation
• ISSN: 0140-7791; 1365-3040
• DOI: 10.1111/pce.13804

Nitrogen (N) supply can limit the yields of soybean [Glycine max (L.) Merr.] in highly productive environments. To explore the physiological mechanisms underlying this limitation, seasonal changes in N dynamics, aboveground dry matter (ADM) accumulation, leaf area index (LAI) and fraction of absorbed radiation (fAPAR) were compared in crops relying only on biological N2 fixation and available soil N (zero‐N treatment) versus crops receiving N fertilizer (full‐N treatment). Experiments were conducted in seven high‐yield environments without water limitation, where crops received optimal management. In the zero‐N treatment, biological N2 fixation was not sufficient to meet the N demand of the growing crop from early in the season up to beginning of seed filling. As a result, crop LAI, growth, N accumulation, radiation‐use efficiency and fAPAR were consistently higher in the full‐N than in the zero‐N treatment, leading to improved seed set and yield. Similarly, plants in the full‐N treatment had heavier seeds with higher N concentration because of greater N mobilization from vegetative organs to seeds. Future yield gains in high‐yield soybean production systems will require an increase in biological N2 fixation, greater supply of N from soil or fertilizer, or alleviation of the trade‐off between these two sources of N in order to meet the plant demand. Symbiotic nitrogen (N) fixation does not preclude N limitation in soybean grown in highly productive environments. Insufficient N supply contrains crop growth and N mobilization to the seeds. Future yield gains in high‐yield soybean production systems will require an increase in biological N2 fixation, greater supply of N from soil or fertilizer, or alleviation of the trade‐off between these two sources of N in order to meet the plant demand.