Terracing Reduces Arbuscular Mycorrhizal fungi Spore Loss through Surface Runoff

Abstract

Surface runoff in agricultural areas promotes the transport of biological structures, such as arbuscular mycorrhizal fungi (AMF) spores, along with mineral particles, nutrients, and organic matter. Limited information exists regarding the relationships between the erosive process and the loss of AMF spores at the hillslope scale, as well as the effect of terracing on these relationships. The objective of this study was to quantify the loss of AMF spores in surface runoff water from agricultural soil managed under no-till and terraced conditions. The research was conducted in the Ribeirão Vermelho watershed, in a hillslope area in Cambé, Paraná, Brazil. Two experimental plots measuring 2.5 hectares each were installed, with one managed without terraces (NTP) and the other with level terraces (TP). At the lower end of the plots, a runoff flow measurement structure (H-channel) was installed to determine the flow rate and suspended spore count. The runoff duration, peak flow rate, and spore count were determined during the period from October 2019 to October 2022. The terrace reduced over 35% of suspended spore loss, and the hysteresis pattern showed a counterclockwise loop in NTP and a clockwise loop in TP for events with higher peak flow rates. The hysteresis pattern indicated rapid spore mobilization and transport in TP, suggesting that spores originated from more distant sources or required more energy for transportation in NTP. Overall, there is evidence that the terrace influences spore variability on the hillslope, reinforcing the need for terracing in agricultural hillslope areas. HIGHLIGHTS• The terracing reduces the peak flow of surface runoff.• The terracing reduces the duration of the surface runoff period.• The lower flow and duration of surface runoff decrease the loss of AMF spores.