The Importance of Fall Fertilizing Fall is the time to feed your root system, but you must fertilize at the right time and in the right amounts.
Improper fertilization can result in a diminished root system.
Fertilizer provides nitrogen, phosphorus, potassium and certain key elements like iron. The root takes these nutrients, plus air and water, from the soil and sends them up to the green grass blades. Sunlight helps turn them into sugars. The sugars are then stored in the root system to power root development during the dormant period, and to give the lawn a quick greening in spring. Nitrogen is needed for leaf growth and a healthy green color.