The Recommendations section of the Soil Test report likely what you have been waiting for: How much fertilizer or lime should you apply for optimum growth of your lawn, garden, or landscape plants?
The first line indicates what the recommendations are for, in this case: Vegetable Garden (provided on the request sheet). Below the solid black line are the Lime, Nitrogen, Phosphate and Potash recommendation, followed by the ratio of nutrients (the NPK ratio found on a fertilizer bag). At the bottom bottom of the page are additional pieces of information including links to follow.
In the example above, the Lime Recommendation is 4500 #ENP/Acre. Information about how to convert that number to pounds of ENP/1000 square feet is listed in the area below the Lime Recommendation.
The section to the right of the Lime Recommendation lists the amount of each of the major macronutrients to apply per year: Nitrogen - 0.15 pounds per 100 square feet, Phosphate (P2O5) - 0.2 pounds per 100 square feet, and Potash (K2O) - 0.3 pounds per 100 square feet.
The line below the total amount of nutrients to apply is "The approximate ratio or proportion of these nutrients is:.." In this case it is listed as 3-4-6. This is also referred to as the NPK (nitrogen, phosphorus, potassium) ratio. The ratio may be multiplied by any number to come up with one that comes close to matching a fertilizer bag. 3-4-6 multiplied by 5 would yield a 15-20-30 (try to match the NPK on the bag closely without going over the nitrogen number). The 15-20-30 NPK ratio on a fertilizer bag means that 15% of the contents of that bag contains the nitrogen fertilizer, 20% is the phosphorus fertilizer and 30% is the potassium fertilizer.
How to calculate how much fertilizer to add:
You have a fertilizer with a 15-20-30 NPK ratio. You will need to know the area of your garden. For this example we will use 500 square feet. Take the nitrogen recommendation from the Soil Test report (0.15 lbs/100 square feet) and divide it by the percent of the nitrogen nutrient in the bag (15 percent is 0.15) which equals 1 lb of fertilizer/100 square feet. You would need 5 pounds of that fertilizer to cover the garden.
Application of phosphorus fertilizer to established lawns in Minnesota is regulated by state law to protect water quality. Fertilizers containing phosphorus cannot be applied unless a soil test shows a need for additional phosphorus to maintain adequate fertility.
Additional information:
- Inorganic and Organic Fertilizers
- Slow Release Fertilizers
- Fertilizer Grades
- Raising Soil pH
- Soil Acidification
- Soil pH Preferences for Selected Landscape Plants
- Calculating Fertilizer Rates from Soil Test Recommendations
- Methods of Applying Fertilizers
- Preventing Pollution Problems from Lawn and Garden Fertilizers
- Yard Waste Compost Application
- Trees, Shrubs, and Fruits, Vegetable
- Flower Gardens
- New Lawns and Turf
- Established Lawns and Turf, Nitrogen Recommendations
- Tree Fertilization: A Guide for Fertilizing New and Established Trees in the Landscape