evaporation

so evaporation is a huge amount of the water used in farming,
when the sun hits the water it evaporates lots,
so keeping the sun off the ground helps save water quite a bit,
I use tiles because I have no flat rocks and not sure about using cardboard
I should go further out with the tiles, and likely will later,
here is a dormant grape with tiles

it also keeps the weeds down,
here is what a grape plant looks like dormant without tiles,

even this one is better than nothing,

so why not wood chips or straw ?
they tend to decay and need changed every year,
and the tile (at least if it is white) reflects the sun up into the plant and should make it grow faster, 
so I like flat rocks or tile,
either way it should save me lots of water.

here is the first grape leaves I have spotted this year,