Synthetic grass and planters on raised beds during the shemitah year

Answer

It is possible to switch from regular turf to synthetic grass during the shemitah year. However, for the sake of marit ayin (appearances) it needs to be clear that you are switching to synthetic grass. So: put out a roll of synthetic grass and a mound of gravel when the work is being done so it will be clear that you are not sowing.

As for the raised beds: if (1) there are plants that are growing there in a permitted fashion (planted and sprouted before the beginning of the shemitah year), and (2) there is a concern that due to the damage to the planters the plants will be significantly damaged, it is permitted to fix these planters. This is provided that the repair will maintain the plants, but not encourage new growth. In any case, it is forbidden to add soil to the planter if it drifted.