Intra‐ and inter‐annual variability of nitrification in the rhizosphere of field‐grown bioenergy sorghum

Abstract

This is an open access article under the terms of the Creat ive Commo ns Attri bution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.

In Silico Evaluation of Plant Nitrification Suppression Effects on Agroecosystem Nitrogen Loss

“…The copyright holder for this preprint this version posted March 2, 2022. ; https://doi.org/10.1101/2022.02.28.482267 doi: bioRxiv preprint suppression measurements occurred three times each growing season, the first occurring about a month after sorghum was planted (late June 2018, early July 2019), the second in the middle of the growing season (late July 2018, early August 2019), and the last near the end of the growing season (late August 2018, early September 2019). We performed ex situ potential nitrification assays on bulk and rhizosphere soils using a method adapted from Belser and Mays (1980), estimating nitrification suppression rates as the difference between rhizosphere and bulk soil potential nitrification rates (Burnham et al 2022).…”

“…Other grass species, including wheat, rye, and wild grasses, also have the capacity for direct BNI, suggesting that the trait may be widespread (O’Sullivan et al 2016, Coskun et al 2017, Subbarao et al 2021). These indirect and direct effects of plants on nitrification can be difficult to partition (Teutscherová et al 2021), particularly in field studies (Burnham et al 2022), so we consider them together as plant nitrification suppression.…”

“…Nitrification suppression is dynamic throughout the growing season over the lifespan of a plant (Nardi et al 2020, Burnham et al 2022), contributing to uncertainty about its effects on N losses from agricultural fields. Plant N demand changes based on growth stage (Moll et al 1982, van Oosterom et al 2010, Ciampitti and Vyn 2011), resulting in temporal variability in plant competition for NH 4 + in the rhizosphere and indirect suppression of nitrification (Burnham et al 2022).…”

“…In recent years, the suppression of rhizosphere nitrification by plants, including biological nitrification inhibition (BNI) by plant root exudates, has received considerable attention as a more cost effective alternative (Subbarao et al 2013b, Coskun et al 2017, Nardi et al 2020). While BNI has been demonstrated in laboratory and greenhouse settings (Subbarao et al 2013a, Janke et al 2018), the effect of plant nitrification suppression on N 2 O emissions and NO 3 - leaching has remained uncertain (Teutscherová et al 2021, Burnham et al 2022).…”

“…We specifically evaluated the potential for nitrification suppression by energy sorghum to reduce field-scale nitrogen losses in the Midwest U.S. Energy sorghum, an emerging bioenergy feedstock crop, is a high-yielding hybrid of biomass and sweet sorghum optimized for high vegetative growth and stem juice production. We calibrated and validated the DayCent-CABBI process-based biogeochemical model for energy sorghum using field measurements from two energy sorghum experiments at the University of Illinois Energy Farm in 2018 and 2019, including estimates of plant nitrification suppression through the growing season (Moore et al 2020b, Quinn 2021, Schetter et al 2021, Burnham et al 2022). To test how the timing of nitrification suppression affects N losses, we compared model experiments all simulating conventional fertilizer application at the time of planting but with different timing and magnitude of nitrification suppression (i.e., no nitrification suppression, with measured levels of nitrification suppression that changed over the growing season and varied inter-annually, and with a consistently high level of nitrification suppression starting one month after planting).…”