Can reclaimed land be converted to arable land? –Positive: Evidences of soil microbial activity from a laboratory experiment

Agriculture is a drive for land reclamation. Reclaiming coastal saline soils is increasingly undertaken as water and heat resources are normally plentiful in coastal land. However, growth of both crops and soil microorganisms is limited due to high cation content and osmotic stress, making saline soils unproductive when converted to arable land. For crops, great efforts have to be made to screen salt-tolerant species suitable for land reclamation. For soil microorganisms in saline soils, will the same separation and domestication of salt-tolerant species be necessary to improve microbial activity as done with crops?

To improve such understandings, we studied coastal saline soils covering non-, mild-, and severe-salinity. Their bacterial diversities were characterized by high throughput sequencing, and microbial metabolic activities analyzed with substrate-induced heat release curves. Abundant and diverse bacterial communities were detected in the severe-salinity soils. While we did not observe soil salinity significantly affected the microbial richness, it did shift soil bacterial community composition. However, the severe-salinity soil was not dominant with salt-tolerant microbial species. With thermodynamic analysis, we discovered glucose amendment efficiently promoted microbial metabolic activity regardless of their community composition. Severe salinity did not inhibit potential metabolic activity of soil microbial community. A further 2-month incubation experiment supported that microbial metabolic kinetics of the severe-salinity soil amended with maize straw recovered and moved toward to the non-salinity soil.

Therefore, our study supported that salt-tolerant species are not indispensable in land reclamation. An addition of labile organic amendments can help to rapidly multiply microbial growth and recover soil microbial functions.