Acidification in corn monocultures favor fungi, ammonia oxidizing bacteria, and nirK-denitrifier groups

ZABALOY, M.C.; HUANG, L.; BEHNKE, G.D.; RODRÍGUEZ-ZAS, S.; RIGGINS, C.W.; VILLAMIL, M.B.

THE SCIENCE OF TOTAL ENVIRONMENT

Elsevier

Lugar: Amsterdam; Año: 2020 vol. 720

0048-9697

Agricultural practices of no-till and crop rotations are critical to counteract the detrimental effects of monocul-tures and tillage operations on ecosystem services related to soil health such as microbial N cycling. The present study explored themain steps of the microbialNcycle, using targeted eneabundance as a proxy,and concerning soil properties, following 19 and 20 years of crop monocultures and rotations of corn (Zeamays L.), and soybean [Glycine max (L.) Merr.], either under no-till or chisel tillage. Real-time quantitative polymerase chain reaction (qPCR) was implemented to estimate phylogenetic groups and functional genes related to the microbial N cycle: nifH (N2 fixation), amoA (nitrification) and nirK, nirS,and nosZ (denitrification). Our results indicate that long-termcrop rotation and tillage decisions affect soil health as it relates to soil properties and microbial param-eters. No-till management increased soil organic matter (SOM), decreased soil pH, and increased copy numbers of AOB (ammonia oxidizing bacteria). Crop rotations with more corn increased SOM, reduced soil pH, reduced AOA (ammonia oxidizing archaea) copy numbers, and increasedAOB and fungal ITS copy numbers. NirK denitri-fier groups were also enhanced under continuous corn. Altogether, the more corn years included in a crop rotation multiplies the amount of N needed to sustain yield levels, thereby intensifying the N cycle in these systems, potentially leading to acidification, enhanced bacterial nitrification, and creating an environment primed for N losses and increased N2O emissions.