Spread damp, used coffee grounds on top of the soil. Turn the coffee grounds into the soil and add a layer of mulch or dried leaves. Tea bags are a nitrogen-rich alternative to coffee.
Crush eggshells and turn them into the soil to provide a nitrogen boost. Small pieces of spoiled produce, bread or rice also provide nitrogen. You can also mix these things into your compost pile.
Sprinkle grass clippings, dried leaves or dead flowers into the soil. This is an ideal way to reuse plant waste that you would otherwise throw away.
Keep the water that you use to boil potatoes or pasta. The water contains some nitrogen and other nutrients that benefit plants. Add cooking water to the soil when you would normally water your plants. Do not water plants with water that contains salt or oil.