Lawns and vegetables have a number of things in common but their nutritional needs are different. Grass, like that which is commonly used for lawns, has specific nutrient needs in order to achieve the density and health most homeowners want. Vegetables, on the other hand, are usually short-lived plants grown for their fruit. While they may require many of the same nutrients, it is proportion that is different and crucial to their success.
Lawns usually put up with a great deal of stress in the forms of frequent mowing, foot traffic and the occasional summer drought. This stress can lead to death of the grass plants. Weakened lawns are susceptible to invasion by weeds or other unwanted plants. In order to have a lush, healthy-looking lawn, lawn fertilizer is applied, usually in the spring and fall. Lawn fertilizer helps revitalize grass plants.
Lawn fertilizers typically have a higher percentage of nitrogen than do garden fertilizers. Nitrogen is the key component for stimulating shoot or foliar growth. It also contributes to root growth. Some lawn fertilizers contain slow-release nitrogen, others a quick-release form and still others contain a combination of both types. Some lawn fertilizers are sold as "weed and feeds" and contain an herbicide to kill common weeds found in lawns.
Like most plants, vegetable plants have three main components--the roots, the leaves and the fruit. Each part requires slightly different nutritional components in order to achieve its purpose. Roots anchor the plant and take in water and nutrients. Leaves are essential for photosynthesis and food production and flowers and fruit are part of the reproductive cycle of the plant and the goal of the vegetable gardener.
Vegetable plants need a well-rounded fertilizer that provides not only nitrogen but potassium and phosphorus. Potassium helps vegetable plants regulate the absorption and use of water. It builds strong roots and stems. Phosphorus helps plants expel excess water and move energy through the plant. Without sufficient phosphorus, vegetable production decreases.
Using Lawn Fertilizer for Vegetables
Because lawn fertilizers are high in nitrogen, they produce lots of vigorous leafy growth when applied to vegetable plants. While plants may appear healthy, they will put all their energy into developing leaves and stems. This will leave little energy for flower production, which is necessary to produce fruits. Reduced production will likely be the result of using lawn fertilizer with high nitrogen content on vegetable plants.
Before using any fertilizer on vegetable plants, it is a good idea to have a soil sample tested for nutritional content. This can be accomplished at your local extension office. The results will show the nutritional composition of the soil and make recommendations, based upon your intended crops, for specific fertilizers or soil amendments to be added. If your soil is nutritionally starved of nitrogen, lawn fertilizer may be a good choice, but only a soil test can tell you that for certain.