Effect of agricultural systems with soybean predominance on mycorrhizal fungi native to contrasting soils of the Pampean region (Argentina)

COMMATTEO JAQCUELINE GISELLE; CABELLO, MARTA; BARBIERI, PABLO ANDRÉS; COVACEVICH FERNANDA

Virtual

Congreso; XXX Reunión Latinoamericana de Rizobiología y V Congreso Latinoamericano sobre Microorganismos Promotores del Crecimiento Vegetal; 2021

Soybean monocrop in the Argentinean Pampas is threatening the abundance and biodiversity of edaphic microorganisms, affecting soil health. Management practices such as cover crops (CC) and crops rotations constitute current trend in the development of sustainable soybean production systems. Arbuscular mycorrhizal fungi (AMF) play a key role in the nutrition and/or growth of most crops. Under contrasting edaphoclimatic conditions, we evaluated the effect of the inclusion of CC and/or rotations for soybean crop on AMF activity and diversity. During 2 consecutive growing seasons (2017/18 and 2018/19 campaign 1 and 2, respectively), soybean monoculture (Sb); cover crop/soybean (CC/Sb); soybean in rotation with corn and wheat (CC/Sb-rot) systems in 3 blocks in a DBCA were evaluated in 3 long-term trials: Balcarce, Marcos Juarez and General Villegas (Sites 1, 2 and 3 respectively). Soil samples associated with roots (0-20 cm) were collected in early autumn, when all plots were with soybean at R6 stage. Abundance of AMF spores was quantified in soil and the taxonomic determination of predominant species was performed (campaign 1), and the degree of mycorrhizal colonization (MC) by native AMF was quantified in roots. In both campaigns and for all the analyzed sites, higher abundance of spores and MC was recorded in the alternative cropping systems (CC/S and/or CC/Sb-rot) in relation to Sb. During both campaigns, Site 1 showed highest number of spores in the alternative systems (average 400 spores. g soil-1), which doubled those in Sb. The MC in alternative systems (average MC 60%) doubled that recorded in Sb roots, particularly during campaign 1. A similar trend was maintained in campaign 2, although with slightly lower values (average MC alternative systems 45%). A similar diversity of AMF was found at the three sites; genera Funneliformes, Acaulospora, Claroideoglomus and Rizophagus were most representative, and Pacispora and Gigaspora were found at lesser extent. In general, fewer dominant genera in the Sb relative to the alternative systems were detected. Our results suggest that sustainable agricultural practices that include both CC and rotations would allow the maintenance and improvement of the quality of soils in systems with soybean predominance.