Dugongs feed by driving the broad, bristled snout into the sediment and uprooting seagrass whole, rhizomes included. The result is a distinctive serpentine feeding trail across the meadow, visible in aerial and diver surveys and used to map dugong activity where the animals themselves are hard to count.
Regular disturbance of this kind favours particular plants. Species such as Halophila and Halodule regrow quickly on disturbed sediment and carry higher nitrogen and lower fibre than slower climax species, so a grazed meadow can trend toward the very seagrasses that suit a dugong best. This is the basis of the cultivation grazing idea.
The strength of the effect is contested and clearly context dependent. It has been documented most convincingly in parts of northern Australia, and how far it generalises to other regions, meadow types and grazing intensities is unsettled. Whether dugongs benefit from it in any measurable way, as opposed to it being an incidental consequence of how they feed, has not been demonstrated.