AUTHOR=Villegas Daniel , Arevalo Ashly , Nuñez Jonathan , Mazabel Johanna , Subbarao Guntur , Rao Idupulapati , De Vega Jose , Arango Jacobo 

TITLE=Biological Nitrification Inhibition (BNI): Phenotyping of a Core Germplasm Collection of the Tropical Forage Grass Megathyrsus maximus Under Greenhouse Conditions

JOURNAL=Frontiers in Plant Science

VOLUME=11

YEAR=2020

URL=https://www.frontiersin.org/journals/plant-science/articles/10.3389/fpls.2020.00820

DOI=10.3389/fpls.2020.00820

ISSN=1664-462X

ABSTRACT=<p>Modern intensively managed pastures that receive large external nitrogen (N) inputs account for high N losses in form of nitrate (NO<sub>3</sub><sup>–</sup>) leaching and emissions of the potent greenhouse gas nitrous oxide (N<sub>2</sub>O). The natural plant capacity to shape the soil N cycle through exudation of organic compounds can be exploited to favor N retention without affecting productivity. In this study, we estimated the relationship between biological nitrification inhibition (BNI), N<sub>2</sub>O emissions and plant productivity for 119 germplasm accessions of Guineagrass (<italic>Megathyrsus maximus</italic>), an important tropical forage crop for livestock production. This relation was tested in a greenhouse experiment measuring BNI as (i) rates of soil nitrification; (ii) abundance of ammonia-oxidizing bacteria (AOB) and archaea (AOA); and (iii) the capacity of root tissue extracts to inhibit nitrification <italic>in vitro</italic>. We then measured N<sub>2</sub>O emissions, aboveground biomass and forage nutrition quality parameters. Reductions on nitrification activity ranging between 30 and 70% were found across the germplasm collection of <italic>M. maximus</italic>. Accessions with low nitrification rates showed a lower abundance of AOB as well as a reduction in N<sub>2</sub>O emissions compared to accessions of high nitrification rates. The BNI capacity was not correlated to N uptake of plants, suggesting that there may be intraspecific variation in the exploitation of different N sources in this grass species. A group of accessions (cluster) with the most desirable agronomic and environmental traits among the collection was identified for further field validation. These results provide evidence of the ability of <italic>M. maximus</italic> to suppress soil nitrification and N<sub>2</sub>O emissions and their relationship with productivity and forage quality, pointing a way to develop N conservative improved forage grasses for tropical livestock production.</p>