Associative nitrogen fixation linked with three perennial bioenergy grasses in field and greenhouse experiments

Wewalwela, Jayani J.; Tian, Yuan; Donaldson, Janet R.; Baldwin, Brian S.; Varco, Jac J.; Rushing, J. Brett; Lu, Haoliang; Williams, Mark A.

doi:10.1111/gcbb.12744

Cited by 14 publications

(11 citation statements)

References 69 publications

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“…Previous work on FLNF in association with other grasses suggests that FLNF may meet upward of 50% of plant N demands (Chalk, 2016; Kuan et al, 2016; Ladha et al, 2016). A similar estimate for switchgrass was confirmed in a recent study which showed potential for switchgrass to acquire one‐third of its N from FLNF (Wewalwela et al, 2020). In the context of previous studies, our work further highlights FLNF as an important N source to switchgrass cropping systems and underscores the potential for successful bioenergy production without fertilizer N addition.…”

Section: Discussionsupporting

confidence: 71%

Temporal dynamics of free‐living nitrogen fixation in the switchgrass rhizosphere

et al. 2021

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Free‐living nitrogen fixation (FLNF) represents an important terrestrial N source and is gaining interest for its potential to contribute plant available N to bioenergy cropping systems. Switchgrass, a cellulosic bioenergy crop, may be particularly reliant on FLNF when grown on low N systems, like marginal lands. However, the potential contributions of FLNF to switchgrass as well as the controls on this process are not well understood. In this study, we evaluated drivers of FLNF rates and N‐fixing microbial (diazotrophic) community composition in field‐grown switchgrass systems over two growing seasons with high temporal sampling. We found that climate variables are strong drivers of FLNF rates in switchgrass systems, compared to other environmental and biological factors including soil nutrients and diazotrophic community composition. Increased soil moisture availability generally promoted FLNF rates, but extreme rainfall events were detrimental. These climate‐related responses suggest a potential for loss of FLNF‐derived N contributions under projected climate shifts. We found a significant, but weak correlation between diazotrophic community composition and FLNF rates. We also observed a significant shift in the diazotrophic community composition between 2017 and 2018 and similarly measured a significant difference in FLNF rates between growing seasons. Lastly, we found that seasonal FLNF N contributions, based on measurement with high temporal resolution, has the potential to meet up to 80% of switchgrass N demands suggesting that FLNF measurements extrapolated from fewer time points or locations may underestimate these potential N contributions.

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Section: Discussionsupporting

confidence: 71%

Temporal dynamics of free‐living nitrogen fixation in the switchgrass rhizosphere

et al. 2021

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“…The reasons miscanthus can maintain high yields without N fertilizer are poorly understood. For example, some studies using N budget estimates for miscanthus suggest a missing N source (Davis et al, 2010; Dohleman et al, 2012), implying endophytic or free‐living N‐fixing bacteria may be one source of this missing N (Davis et al, 2010; Eckert et al, 2001; Keymer & Kent, 2014; Wewalwela et al, 2020). Another plausible explanation is that miscanthus increases net N mineralization (N min ) (Davis et al, 2013, 2015), thereby meeting N demands with N mobilized from SOM.…”

Section: Introductionmentioning

confidence: 99%

Soil net nitrogen mineralization and leaching under Miscanthus × giganteus and Zea mays

et al. 2021

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The winter fallow period common in annual cropping systems leaves soils vulnerable to erosion and nutrient loss, especially to nitrogen (N) leaching. This vulnerability can be mitigated with perennial crops that have living roots in the ground year‐round. The mechanisms, magnitude, and consistency with which perennial crops retain N are not clear. We used an experiment to test whether a perennial crop, miscanthus (Miscanthus × giganteus Greef et Deu.), would leach less N than continuous maize (Zea mays L.) and how soil net N mineralization (Nmin) may explain observed leaching under varied environment and management conditions. The experiment included three crossed factors: (1) cropping system (maize, juvenile miscanthus = 1–2 years old, mature miscanthus = 3–4 years old); (2) N fertilization (0 and 224 kg N ha−1); and (3) environment (four site‐years at two locations in Iowa, USA, that differed in climate and soil fertility). We measured N cycling dynamics, including: inorganic soil N (ammonium + nitrate), in situ Nmin, N leaching, crop N uptake, and calculated system N use efficiency. There were many complex interactions among factors. On average, cumulative Nmin under juvenile miscanthus was 111% greater than maize, but as miscanthus matured, there was no difference in Nmin between the perennial crop and maize. There was no difference in N leaching between juvenile miscanthus and maize, but mature miscanthus decreased N leaching by 42% and 88% compared to maize (with and without N fertilization, respectively). Across all treatments, there was no relationship between Nmin and N leaching, suggesting other mechanisms are regulating N leaching. Overall, mature miscanthus shows promise as a tool to reduce N losses in areas dominated by annual row‐crops.

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“…Nebeská et al (2018) observed that the G + /G − and fungal/bacterial ratios in organic and toxic metals polluted soil increased after 2 years of Miscanthus cultivation through a greenhouse pot experiment. Several studies have reported the existence of diazotrophs in bulk and rhizospheric soil of land with cultivated Miscanthus (Zhao et al, 2020), and documented their considerable contribution to Miscanthus growth based on an analysis of a N fixation gene ( nifH ; Li et al, 2016; Soman et al, 2018; Wewalwela et al, 2020), but lacked revelations of the responses of soil N‐cycling‐related genes and the microbiome for long‐term Miscanthus conversion in Northern China.…”

Section: Introductionmentioning

confidence: 99%

Cropland‐to‐Miscanthus conversion alters soil bacterial and archaeal communities influencing N‐cycle in Northern China

Zhao

Yue

et al. 2021

GCB Bioenergy

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Miscanthus spp. are increasingly cultivated in cropland worldwide due to their bioenergy potential and multiple ecological services. Effects of long‐term cropland‐to‐Miscanthus conversion without N fertilizer on soil microbiome and N cycling largely remain unknown. We aimed to explore the effects of Miscanthus conversion on soil microbiome and N cycling over a 15‐year period. We analyzed diversity, composition, and abundance of bacterial and archaeal communities using 16S rRNA amplicon sequencing, and abundances of N‐cycling‐related genes using quantitative polymerase chain reaction of 0–10 cm soils collected from bare land, cropland, 10‐year Miscanthus × giganteus, and 15‐year Miscanthus sacchriflorus land in Beijing. Conversion decreased soil sand and micro‐aggregate proportion, nitrate N (NiN), available phosphorus levels, conductivity, temperature, and pH, while increasing proportion of soil clay and macro‐aggregate (MAA), soil organic C (SOC), available N (AN), exchangeable Mg2+ (EMg2+), and available potassium (AK) contents as well as microbial C/N. Consequently, diversity, composition, and abundance of soil bacterial community exhibited larger changes than those values of archaeal community after conversion. Soil AP, EMg2+, AK, and SOC were key factors in shifting microbiome from the cropland to Miscanthus pattern. Moreover, abundances of bacterial and archaeal communities and the N fixer gene nifH increased, whereas that of the bacterial ammonia monooxygenase gene decreased. The copies of other N‐cycling‐related genes in the two Miscanthus lands seemed similar to those values of cropland. The nifH copies negatively correlated with soil NiN and positively correlated with AN, EMg2+, ECa2+, SOC, AK, and MAA. We conclude that changes in soil microbiome pattern induced by the variation of soil properties enhance microbial N fixation potential, maintaining stable N levels and robust N cycling with lower N leakage risk after conversion. These results should inspire farmers and governments to large‐scale use Miscanthus on marginal cropland in Northern China.

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Associative nitrogen fixation linked with three perennial bioenergy grasses in field and greenhouse experiments

Abstract: This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.

Cited by 14 publications

References 69 publications

Temporal dynamics of free‐living nitrogen fixation in the switchgrass rhizosphere

Temporal dynamics of free‐living nitrogen fixation in the switchgrass rhizosphere

Soil net nitrogen mineralization and leaching under Miscanthus × giganteus and Zea mays

Cropland‐to‐Miscanthus conversion alters soil bacterial and archaeal communities influencing N‐cycle in Northern China

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