Choosing and applying the correct fertilizer for the home garden may be a bit confusing, especially if you are new to gardening. Each fertilizer is a special blend of nutrients, typically labeled by three numbers to represent the percentage of nitrogen (N), phosphorous (P) and potassium (K) in the formula. Fertilizer labeled as 10-10-10 contains 10 percent nitrogen, 10 percent phosphorous and 10 percent potassium. 5-10-10 fertilizer contains 5 percent nitrogen, 10 percent phosphorous and 10 percent potassium. The remaining percentage is composed of inert ingredients. The specific formula your garden needs depends of the condition of your soil and the needs of specific plants.
Test your garden soil to determine the specific needs of your soil. Inexpensive kits from the hardware store or garden supply center provide a quick assessment of the nutrients available in your soil. Follow the directions with the kit to gather the soil sample and test your soil.
Determine the correct formula of fertilizer for your specific gardening area by reading the instructions in the soil test kit for amending your soil. Soils with balanced nutrients--even if all nutrients are low--require a balanced fertilizer. Choose fertilizer with formulas such as 10-10-10 or 18-18-18 for balanced soils.
Match the formula of the fertilizer to your soil. If your soil test indicates nutrients are not balanced, choose a formula with higher percentages of those nutrients your soil lacks, and lower percentages of nutrients you soil contains. For example, 5-10-10 fertilizer is a good choice for soil with a good nitrogen content that lacks phosphorus and potassium.
Measure your garden area in feet to determine the square footage of the garden. Convert inches to decimals--3 inches = .25, 6 inches=.50, 9 inches =.75. To calculate the number of square feet, multiply the width of the garden by its length.
Locate the application rate on the container of fertilizer. Application rate is typically listed per 100 square feet, but may be listed per 1,000 square feet, if the fertilizer is sold for commercial use. Divide the amount per 1,000 feet by 10 to determine the amount required for 100 square feet.
Measure the appropriate amount of fertilizer for your garden area. Spread the fertilizer over the entire area, unless directions indicate otherwise. Till the fertilizer into the soil with a garden tiller.