Nanobubble Oxygenated Drip Irrigation Improves Soil Physical Structure Via Microbially Mediated Effects

Abstract

Compactness and lack of permeability have become common problems in continuously cultivated soils, severely inhibiting crop root respiration and nutrient uptake and adversely affecting soil fertility and crop yield. Regulation of the microbial community in the plant rhizosphere has been envisaged as a promising approach to alleviate these physical damages in soil. Here, delivering oxygen to the crop root zone by nanobubble oxygenated subsurface drip irrigation (NBO2) system was proposed as new technology to improve the soil structure in continuously cultivated soils. The effects of NBO2 on the soil physical structure and the bacterial community were investigated using X-ray tomography and 16S rRNA amplicon sequencing. The results indicated that NBO2 significantly improved the soil structure and permeability, increasing the total porosity and pore connectivity by 43.2% and 355.1%, respectively. The structural equation model (SEM) demonstrated that NBO2 had direct impacts on soil structure by increasing microbial community diversity and changing interactions among microbial species. In addition, NBO2 directly impacted the soil structure by reducing the formation of soil biofilms and the stability of soil macroaggregates. The NBO2 treatment indirectly affected the soil structure by altering the community composition and promoting the decomposition of unstable organic carbon, resulting in improved soil porosity and pore connectivity. Our results highlight the efficiency of NBO2 in improving soil physical structure and provide mechanistic knowledge on the microbial-mediated processes for the improvement of crop yield and quality using oxygenated drip irrigation.

Keywords: nanobubble water irrigation, microbial community, soil structure, pores, Soil Fertility