Fertilizers add nutrients to soil and enhance the output of vegetable gardens. Busy moms can get by with fertilizing their gardens only twice a year if they use the proper formulation and amount of fertilizer. Nitrogen helps plants develop leaves, while phosphorus and potassium promote root, fruit and overall plant growth. Commercially prepared N-P-K fertilizers contain nitrogen, phosphorus and potassium. A complete fertilizer has all three of these essential nutrients and is generally a good choice for the home vegetable garden.
Just before you plant the vegetable garden, apply fertilizer so that the young plants have nutrients for an early growth spurt. Spread 1 pound of granular complete fertilizer, such as 10-10-10 fertilizer for leafy greens or low-nitrogen 6-12-18 fertilizer for root or fruit vegetables, over every 100 square feet. Work the fertilizer 6 inches into the soil with a spade or tiller. Water the soil to move the fertilizer into the soil. Keep children away from chemical fertilizers, and wear gloves during application to prevent skin irritation.
During the growing season, plants use up soil nutrients as they grow, and water washes nutrients from the soil. Your vegetable garden needs an additional pound of complete fertilizer per 100 square feet six weeks after planting. To prevent burning the plant roots, keep the fertilizer granules 6 to 12 inches away from plant stems as you spread the fertilizer over the soil. Rake in the fertilizer and water the fertilized area thoroughly.
Most vegetable plants grow as annuals and die after one growing season. Perennials, such as asparagus (Asparagus officinalis), live for more than one growing season and need a different fertilizer schedule. Before planting, mix a 4- to 6-inch layer of compost or manure in the soil so that the plant will have rich soil for years. During the first three years, fertilize asparagus, which grows in U.S. Department of Agriculture plant hardiness zones 4 through 8, as you fertilize annual vegetables. In the fourth year, wait until just after the first summer harvest to apply fertilizer so that the plants can store nutrients for the next year.
Do not use lawn fertilizer, which may contain weedkiller that can harm vegetable plants. If you add fertilizer too frequently, your plants may develop abundant leaf and stem production with few fruits. Beans and other legumes need less nitrogen than other crops because they get their nitrogen from the air. For example, bush beans need 2 cups of 5-10-10 fertilizer per 100 row feet at planting time. To avoid damage from improper fertilizing, group plants with similar fertilizer needs together, such as legumes, perennials or leafy green vegetables.