Fertilizing your vegetables in the garden gives them the nutrients to thrive, but using the wrong type of fertilizer at the wrong time causes more harm than good. Vegetables need nitrogen, phosphate and potassium. In fertilizer blends, the percentage of nitrogen comes first on the label, followed by phosphate and then potassium; therefore, a 10-10-10 fertilizer blend has equal amounts of each. Follow the application recommendations for your vegetable types and soil type when choosing fertilizer.
Test the soil for acidity by using a soil pH test kit from a nursery or home improvement store. Conduct the test and, depending on the results, apply the proper element in fall so the soil is ready by spring. If the soil needs lower acidity, add lime in the amount recommended by your test. Add sulfur in the recommended amount if it needs less alkalinity.
Replenish organic material in the soil before planting the garden in spring. Apply a 3-inch layer of mature compost over the entire vegetable bed. Till the compost to a 6- to 8-inch depth by using a power tiller or hoe.
Apply a liquid-balanced vegetable garden fertilizer, such as 10-10-10 or 12-12-12, at planting time. Dilute the fertilizer in water as detailed in the label instructions, then apply the solution to a 6-inch circle around each plant. Avoid applying the fertilizer directly to the plant.
Apply further fertilization as required for each specific vegetable variety. In general, apply a nitrogen-rich fertilizer (such as 20-10-10) when plants begin to set fruits. Dilute in water before applying, then fertilize around, not directly on, the plant.
Fertilize leafy vegetables, such as lettuce or cabbage, when they develop their fifth sets of true leaves. Use liquid nitrogen-rich fertilizer around but not on the plants.