Tomato yield increase in drip irrigation improved by micro-nanobubbles

https://www.sciencedirect.com/science/article/abs/pii/S0167198725001898

• Compared with low dissolved oxygen (5 mg·L-1), high dissolved oxygen can increase the tomato yield by 87.20 %.
• High dissolved oxygen (30 mg·L⁻¹) is beneficial to the root–soil interdomain bacterial network.
• Different dissolved oxygen under excessive irrigation conditions regulate rhizosphere soil and root-endophytic bacteria.

The purpose of this study was to explore the microecological mechanism 

by which micro/nanobubble-oxygenated drip irrigation promotes the 

growth of crops in saline soil under excessive quantities of irrigation water. 

This study focused on investigating the response of root bacterial communities 

to the cumulative effects of excessive irrigation water at different dissolved 

oxygen (DO) concentrations and analyzing the changes in the root–soil 

interdomain bacterial community network and their relationships with the

 soil microenvironment in the root zone and tomato yield. Compared

 with the noncultivated treatment in saline soil (CK), the high-DO concentration

 treatment (30 mg·L⁻¹, i.e., DO₃₀) led to a 94.51 % reduction in the soil electrical

 conductivity (EC) in the root zone, and the Shannon index of the rhizosphere soil

 bacterial communities increased by 3.94 %. DO₃₀ significantly increased the relative 

abundance of Bdellovibrionota, which are nitrate metabolism-related root endophytic 

bacteria, and Sphingomonas, which are root endophytic bacteria with a nitrogen fixation 

function. Additionally, the average root diameter and root volume of the tomato

 root system increased by 51.93 % and 151.36 %, respectively, compared with those

 under the low-oxygen (5 mg·L⁻¹, i.e., DO₅) treatment. These changes enhanced 

the influence of root–soil bacterial communities on tomato growth; therefore, 

the tomato yield increased by 87.20 % and 13.22 % compared with that under 

the DO₅ and moderate-DO concentration (15 mg·L⁻¹, i.e., DO₁₅) treatments, 

respectively. Compared with that under the CK treatment, the Shannon index

 of the rhizosphere soil bacterial community under the DO₁₅ treatment increased

 by 4.34 %, and the relative abundances of the beneficial root endophytic bacteria 

Nitrospirota, Myxococcota, Acidobacteriota, and Gemmatimonadota significantly

 increased. However, the effects on average root diameter, root volume, and soil

 EC reduction in the root zone were inferior to those under DO₃₀, limiting

 nutrient uptake by the roots. As a result, the yield was lower than that under

 DO₃₀ but 36.82 % higher than that under DO₅. Therefore, when micro/nanobubble-oxygenated

 drip irrigation under excessive irrigation conditions was used to promote tomato

 production in saline soils, DO₃₀ was preferentially recommended, followed by DO₁₅.