Long Island soil: sandy, fast-draining, and fixable

Most of us are gardening on glacial outwash — sand and gravel that drains before your plants get a drink. What has actually moved the needle in our beds: 1. Compost, every season. Two inches worked in each spring changes water holding more than anything else. 2. Mulch heavy. Straw or leaf mulch keeps the top four inches from baking dry in July. 3. Test before you lime. Our soil trends acidic, but guessing wastes money. Cornell Cooperative Extension in Riverhead runs cheap soil tests. 4. Cover crop the empty beds. Winter rye in October, chopped in April. What is your amendment routine? Anyone had luck with biochar out here?