Combine vegetables in a very large bowl. Sprinkle with salt; add cold water to cover. Let stand at room temperature for 2 hours.
Pour vegetable mixture into a colander set in the sink. Rinse with fresh water and drain well.
In a 6- to 8-quart stainless-steel, enamel, or nonstick heavy pot, combine sugar, vinegar, mustard seeds, celery seeds, and turmeric. Heat to boiling. Add drained vegetables; return to boiling. Cook, uncovered, over medium-high heat for 10 minutes, stirring occasionally.
Ladle relish into hot, clean pint canning jars, leaving 1/2-inch head space. Remove air bubbles and wipe the jar rims; adjust lids. Process filled jars in a boiling-water canner for 10 minutes (start timing when water returns to boil). Remove jars; cool on racks.