Soil Macro-Aggregate Enhanced By Soil Saprophytic Fungi Composition and Abundance in Intercropping System.

Soil micro-organisms play pivotal roles in soil aggregate formation. However, little attention has been paid to the change of soil aggregates affected by plant-plant interactions especially in agricultural ecosystems. Previous study has proved that intercropping enhances proportion of larger water stable macroaggregate of soils.  Trying to address this issue, we hypothesized that increased soil macro-aggregates under intercropping are related to the biomass and community composition of soil microorganisms. Thus, three field experiments were conducted in Oasis in Northwest China. Experiment 1 was three factorial design, where first factor was Rhizobium-inoculation and non-rhizobium inoculation, second factor was different N fertilization rates (0, 75, 150, 225 and 300 kg/ha), and third factor was cropping systems including faba bean/maize intercropping and corresponding monocultures, located at Hongsipu in Ningxia Province. Experiment 2 and Experiment 3 were two factorial design, where first factor was P fertilization rates (0, 40 and 80 kg/ha) and second factor was cropping systems including faba bean/maize, chickpea/maize, soybean/maize and turnip/maize intercropping and their corresponding monocultures, located at Jingyuan and Baiyun, Gansu Province. The results showed that (1) Soil water stable aggregate (WSA) (> 2 mm) was increased by17.8% (Exp.1), 34.4% (Exp.2) and 15.5% (Exp.3) in intercropping systems compared with corresponding monocultures. (2) There were 13.4%, 23.7% (Exp.2) and 24.6%, 25.5% (Exp.3) higher total fungal biomass and non-arbuscular mycorrhizal fungal biomass in intercropping soil than monoculture soil, while there were 22.5% (Exp.1) and 6.7% (Exp.2) less soil bacterial biomass in intercropping than monocultures. (3) Relative abundance of soil saprophytic fungi was significantly positive correlation with soil water stable macro-aggregates (> 2 mm). Our findings confirm the increases of soil WSA (> 2 mm) under intercropping system is conducive to the increase of soil fungal biomass, especially the saprophytic fungi relative abundance and the decrease of soil bacterial biomass.