Release of organic substance from roots of plant into the surround soil is termed by rhizodeposition. Thereby, this substance such as C can be used by soil microorganisms which subsequently affect C and nutrient cycling in ecosystems.

However, how much rizho- C will be utilized by microorganism and which predominant microbial groups utilizing rizho- C with Nitrogen addition still need to investigate.

To study how rice plants can significantly modify their soil environment (rice rhizosphere effect) through carbon rhizodeposits from roots into the surrounding soil, scientists from the Institute of Subtropical Agriculture (ISA) of Chinese Academy of Sciences in cooperation with Georg-August University of Gottingen, Germany and Australian Centre for Ecogenomics, School of Chemistry and Molecular Biosciences, University of Queensland,Australia installed an experiment.

In their experiment, they collected the paddy soil samples and invented a method to separate the soil sample into rhizosphere soil and non rhizosphere soil by using bag (16.7 cm height×6 cm i.d., 30 μm mesh). Then the rice were grown in a pots experiment filled with rhizosphere (soil within the bag) and non-rhizosphere (soil out of the bag) soil portions with or without N fertilization (0 and 225 kg N-NH4⁺ ha^-1), and subject to ¹³CO₂ pulse labeling at five growth stages: tillering, elongation, heading, filling, and maturation.

At the beginning of their study, they found that the ¹³C assimilated into microbial biomass changed rapidly before elongation stage and then remained stable.

Comparison to unfertilized treatment, they also found the addition of Nitrogen fertilizers caused increasing of ¹³C assimilated by microbial biomass in both rhizosphere and noun rhizosphere soil.

They interoperated this by the excessive increase in phytomass formation and root exudates after N fertilization. Therefore they concluded that carbon transfer between rhizosphere and non-rhizosphere strongly affected by N fertilization and thereby affected soil C-cycling.

The study entitled " Initial utilization of rhizodeposits with rice growth in paddy soils: Rhizosphere and N fertilization effects" was published in Geoderma. Details can be found at https://www.sciencedirect.com/science/article/pii/S0016706118307493.

The study was supported by the National Natural Science Foundation of China, Youth Innovation Team Project of ISA, CAS.

Contact: GE Tida

E-mail: gtd@isa.ac.cn

Institute of Subtropical Agriculture, Chinese Academy of Sciences