Rhizosphere microbiota alleviate As accumulation in maize intercropped with peanut in long-term Cd and As co-contaminated farmland

Abstract

Root-associated microbiota play an important role in regulating heavy metal transfter from soil to crops in contaminated areas. Maize-peanut intercropping is a cultivation pattern that directly influences the composition and function of the root-associated microbiota in farmland. However, it remains unclear whether this intercropping affects the accumulation of As and Cd in the edible parts of crops by altering the root microbial community in long-term As and Cd co-contaminated farmland. A field experiment was conducted to explore the mechanisms of intercropping maize-peanut on regulating the behaviors of As and Cd in soil-crop system by recruiting the specific root-associated microbial communities. The results demonstrated that intercropping maize-peanut significantly decreased the As concentration in the grains of intercropped maize (IM) up to 61.0 ​% compared with monocropping maize. Specifically, at the jointing stage, IM recruited the distinct root-associated microorganisms, including Actinobacteria Lechevalieria, Nocardioides, Agromyces, and Blastococcus, and Alphaproteobacteria norank_f__Geminicoccaceae. These microbial communities were closely associated with the As bioavailability in the rhizosphere soil and As accumulation in maize tissues, especially grain-As of IM. However, intercropping maize-peanut had no significant effect on Cd concentrations in the grains of either maize or peanut. This study verified that the intercropping maize-peanut might be a better approach to guarantee the safety of crop products in As-contaminated soil, but not in Cd- or Cd-As co-contaminated farmland.