If you broadcast salt, go slow and low so granules don't bounce into adjacent beds. Salt in soil can ruin structure, caking the soil so water doesn't flow, and burn plants' roots. To save it for another year, keep yours in full sun and water it regularly until you move it outside in May. Forced tulips, daffs, and other hardy bulbs can also be nurtured until spring and then planted out. Every one I get eventually starts dropping leaves and then either dies or looks so bad I wish it would die and put me out of its misery.
Plants drop leaves in response to stress, which is usually linked to changes in growing conditions.
Pay attention to light, temperature and humidity at the greenhouse when you buy a plant and try to give it that same situation in your home. When foliage goes limp, yellows or browns and hangs on, parting from branches only if pulled, overwatering and root rot may be the problem. Should the leaves curl, dry up and remain attached, underwatering could be the cause. If leaves drop very suddenly, look for cold drafts or a surface under the plant that becomes very cold at night. Leaf fall concentrated on one side of a plant may be due to hot, dry air blowing from furnace ducts.