Effect of water oxygenation on the microbiota of compacted soils in broccoli cultivation

Soil compaction is an increasing problem in Europe, with more than 29% of subsoils affected. Soil mecha
nical impedance is caused primarily by natural processes and by the use of heavy machinery in agricultural 
practices. Plant roots are strongly influenced by the physical properties of the soil. Soil compaction, along 
with changes in soil water potential, are major factors contributing to high mechanical impedance or 
excessive soil strength. These factors not only affect the plant root system—leading to changes in root 
morphology—but also impact the soil microbiota. In this study, the effect of two levels of soil compa
ction on broccoli cultivation and soil biology was evaluated. Broccoli plants were grown in open-bottom 
pots placed in direct contact with the soil and subjected to different compaction levels (0, 200, and 400 
psi), with and without oxygenation applied through the irrigation water. This resulted in six treatments: 
0, 0+O₂, 200, 200+O₂, 400, and 400+O₂. Plant growth and final yield were measured, along with soil en
zymatic activities and metabarcoding analyses to assess variations in fungal and bacterial populations. 
While urease and dehydrogenase activities showed no significant differences, an increase in phosphatase 
activity was observed in all compaction treatments. β-glucosidase activity increased with oxygenati
on at all compaction levels, indicating a promoted microbiome activity by oxygenation. Metabarcoding 
analysis revealed that bacterial alpha diversity was lowest in the 0+O₂ treatment and highest in the 400 
treatment, where high compaction (400 psi) promoted anaerobic bacterial populations compared to the 
control (0) and 400+O₂ treatments. Both compaction and oxygenation induced changes in bacterial and 
fungal communities suggesting that oxygenation can mitigate the negative effects of high compaction 
and improve soil health