One of the best ways to improve soils nutrient content is by adding organic fertilizer. This is usually in the form of manure from cows, pigs, rabbits, bats, chickens, and horses. Do not use droppings from carnivorous animals. Manure should be aged properly before it is used. This can be done by allowing the manure to dry or by composting it. Once you add the manure, mix it into the soil well. If you are adding it in the spring, make sure to do it several weeks before you begin planting.
Compost