Simultaneous gains in grain yield and nitrogen efficiency over 70 years of maize genetic improvement

Abstract

The competing demands of increasing grain yields to feed a growing population and decreasing nitrogen (N) fertilizer use and loss to the environment poses a grand challenge to farmers and society, and necessitates achieving improved N use efficiency (NUE) in cereal crops. Although selection for increased yield in maize has improved NUE over time, the present understanding of the physiological determinants of NUE and its key components hampers the design of more effective breeding strategies conducive to accelerating genetic gain for this trait. We show that maize NUE gains have been supported by more efficient allocation of N among plant organs during the grain filling period. Comparing seven maize hybrids commercialized between 1946 and 2015 from a single seed company in multiple N fertilizer treatments, we demonstrate that modern hybrids produced more grain per unit of accumulated N by more efficiently remobilizing N stored in stems than in leaves to support kernel growth. Increases in N fertilizer recovery and N harvest index at maturity were mirrored by a steady decrease in stem N allocation in this era study. These insights can inform future breeding strategies for continued NUE gains through improved conversion efficiency of accumulated plant N into grain yield.

Relationship of in‐season soil nitrogen concentration with corn yield and potential nitrogen losses

“…The period of maximal N accumulation in corn plants (∼8.9 kg N ha −1 d −1 ) occurs between V10 and V14 in modern hybrids (Bender, Haegele, Ruffo, & Below, 2013; Mueller, Messina, & Vyn, 2019), which generally coincides with conditions favorable for N mineralization (Griffin, 2008). This may explain why the critical levels during mid‐vegetative growth remained relatively constant (ranging from 14.7 to 16.3 mg N kg −1 ), with mineralization helping to maintain SMN levels despite rapid crop uptake.…”

Nitrogen rate impacts on tropical maize nitrogen use efficiency and soil nitrogen depletion in eastern and southern Africa

“…When 40 kg N ha -1 was applied in Harare, however, the NRE value spiked to 1.8 kg kg -1 , exceeding all values found in the literature. We believe that this exceptionally high NRE value is not an anomaly, but rather, points to the potential of newer maize hybrids to further deplete the soil of inorganic N at lower N rates (Mueller et al 2019).…”

Genetic Progress of Seed Yield and Nitrogen Use Efficiency of Brazilian carioca Common Bean Cultivars Using Bayesian Approaches

“…In common bean, there are still no studies quantifying the genetic progress for NUsE. On the other hand, an increase in NUsE has been reported in several other crops (Laidig et al, 2017;Stahl et al, 2017;Mueller et al, 2019).…”

“…Possibly the common bean breeding programs are not focusing in the improvement of NUsE since common beans are able to fix N 2 by symbiosis. However, NUsE genetic progress and their components have been reported in other crops that do not have this N 2 fixation ability, such as, wheat (Laidig et al, 2017), maize (Mueller et al, 2019), and oilseed rape (Stahl et al, 2017). In addition, the evaluation and selection for NUsE is considered an extremely expensive process and may not be implemented in breeding programs soon.…”

“…N is the most important macronutrient influencing common bean yield (Barros et al, 2018). Therefore, the development of cultivars that have greater N use efficiency (NUsE) is considered one of the main strategies to reduce the amount of chemical fertilizers in sustainable farming systems (Mueller et al, 2019).…”