Integrated reclamation of saline soil nitrogen transformation in the hyphosphere by earthworms and arbuscular mycorrhizal fungus

Abstract

Soil salinization greatly alters nitrogen cycling and threatens the sustainable productivity of food production areas worldwide. A two-compartment microcosm was used to investigate the integrated effects of arbuscular mycorrhizal fungi (AMF) hyphae and earthworms on nitrogen transformation at different incubation times in saline soil. The treatments were designed with or without hyphae and with or without earthworms harvested at day 40 or 60 in the hyphal compartments (HC). Salt concentration, soil aggregate-size distribution, soil organic carbon, hyphal length density (HLD), total glomalin-related soil protein (TGRSP), inorganic nitrogen concentrations, microbial biomass nitrogen (MBN) and the N-functional marker genes were determined in the HC. The results showed that earthworms and AMF hyphae decreased the soil salt concentration, while increased the soil NO3−-N, NH4+-N, MBN and the abundance of nifH and AOB amoA genes. Earthworms and AMF hyphae could independently or cooperatively affect soil macroaggregates. Earthworms and AMF hyphae affected soil NH4+-N and NO3−N by increasing the soil macroaggregates and MBN. At day 60, earthworms affected soil NO3−N by regulating the abundance of nifH and AOB amoA genes, while AMF hyphae increased soil NH4+-N by regulating the HLD and TGRSP. In conclusion, earthworms and AMF hyphae cooperatively affected soil NO3−-N and NH4+-N by regulating the soil macroaggregates, microbial biomass nitrogen and N-cycling bacteriain saline soil. The results would be useful in reclamation programmes undertaken to rehabilitate land sources that suffer from problems associated with soil salinization.