The maize/cassava relay intercropping system can be a specific and efficient cropping pattern in a tropical/subtropical field. Relay intercropping systems contribute to the optimization of land use, fostering sustainable and efficient agriculture. This study entails a first-year comparative intercropping experiment using maize (Zea mays L.) and cassava (Manihot esculenta Crantz). We determined the soil nutrient contents and physicochemical properties as well as the microbial communities by high-throughput sequencing. We found that the relay intercropping system changed the bacterial community structure, especially the rhizosphere microorganisms. The bacterial community was characterized by a higher abundance of the phyla Chloroflexi, Proteobacteria, and Actinobacteria and of the genus AD3, which are related to nutrient cycling and decreased bioavailability of Cd. At the same time, the relay intercropping system reduces the relative abundance of pathogenic bacteria and biomarkers of organic pollution. The relay intercropping systems significantly boosted soil pH and available K levels in addition to the monocropping yield. The results of this study suggest that maize/cassava relay intercropping, starting from the first year, not only provides a stable supply of food and income due to the diversified cropping systems but is also beneficial for the improvement of soil quality and the soil microbial community.

Metolachlor is extensively used and the most persistent chloroacetamide herbicide, thereby which its metabolites have been frequently detected in soils and surface and groundwaters. Microbial degradation is predominantly responsible for the removal of metolachlor from soil and water. However, few microbial strains reported previously are highly efficient in degrading potentials for metolachlor. We isolated the fungal strain MET-F-1 from an activated sludge, characterized as Penicillium oxalicum, which could degrade 88.6% of 50 mg/L metolachlor coupled with 0.1% glucose plus 0.1% yeast extract within 384 h under optimal conditions. Compared with metabolites produced by previously isolated microorganisms, different degradation products, i.e., MOXA, M2H, and MDES, detected by high-performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS), were produced through hydrolytic and reductive dechlorination by MET-F-1. This is the first report on the degradation of metolachlor by Penicillium oxalicum sp. Furthermore, field plot experiments using the wheat bran inoculum method were performed and demonstrated good metolachlor-degrading activity of this strain. This study serves as a steppingstone to promote MET-F-1 strain usage as a promising agent for metolachlor-contaminated soil remediation.