I have seen shade tarps over acres upon acres of ginseng plants. These don't keep out the rain, just excesive sunlight, and are not easily retractable.

A cover that would not collapse under the weight of rain in sufficient amounts to damage crops would likely be heavy, as well as difficult to roll over the crops at a moments notice. And the expense would probably make it impractical for most craps.

Oh, drat. . . that last word is crops.

Really need an edit feature. . .

we can make heavy covers with the polyethelene which are major concern for envionmentalist these days. So we can also inturn help the pollution control unit.

My farm/ranch in 5000 acres...thats a lot of shrink wrap. And that is not even a measurable portion of the area that would have to be covered to actually have an impact on crop salvation. I think money would be better spend on weath mondificaiton, try to avoid the hail storms and such all together.