I'm planting a backyard vineyard on the coast in very fertile wet soil in the winter, and dry in summer. Should I add river rock to the soil to enhance winter drainage when I dig the rows? Also, the pH is at 5.8 or so. Is it imperative to add limestone to buffer. I'll be planting Pinot noir, and either Pinot Gris or Muller Thurgau. Any thoughts out there? Thanks.