If high quality hay is your goal, don't delay harvest. However, if you're looking to rebuild your hay supply, letting it grow almost until bloom will provide more feed while using water resources more efficiently.
No-till seeding alfalfa can help preserve crop residue on the soil surface, reduce soil erosion, limit weed seeds on the soil surface, and perhaps most importantly this year, help conserve soil moisture.
Bitter cold spells and desiccating winds in early winter may have endangered alfalfa stands. Evaluate alfalfa stands soon to determine their viability and the potential need for replanting or rotating to another crop.
Five years of grazing research in eastern Nebraska showed that brome/legume pastures produced almost four-tenths of a pound higher average daily gain on yearlings than did straight brome pastures fertilized with 50 lbs of nitrogen. Adding legumes to your pasture mix may be just the boost your production system needs.