A soil test report gives you precise nutrient requirements for the soil type and plant type in your situation.
Sixteen nutrients are necessary for plant growth and development. Thirteen of them are usually available from the soil. However, three nutrients need to be added to soil to help plants along. They are nitrogen, phosphorous, and potassium (N,P & K). Fertilizers provide these essential elements. When fertilizer is applied in the correct amount, plants use up the nutrients and no excess is left to leach away. You can't see the fertilizer in the ground. So, how do you know how much fertilizer to apply to add the correct amount?
Some people estimate the amount of fertilizer to add to their lawn or garden. Usually, too much fertilizer is applied when you estimate. The unused fertilizer then leaches to the ground water and ends up in nearby ponds and creeks. That leads to an over-abundance of nutrients in the water and that can harm the aquatic habitat. The other risk associated with estimating is that you can also underestimate the amount of fertilizer to add. In which case, your lawn or garden does not have the necessary nutrients to thrive. Either way you look at it, estimating the amount of fertilizer to apply is not beneficial to your lawn or garden nor the community around you.
How is Soil Tested?
The NC Dept. of Agriculture is a state agency that tests soils for free. Cardboard sampling boxes are available at extension offices and at Soil and Water Conservation District offices. You fill the box ¾ full with soil and send it to the testing facility in Raleigh. Sample three to four months before fertilizer applications to ensure there is enough time to get the report back.
There are also soil test kits for sale at local garden centers. These range from $3 to $7.
Small garden trowel
Be sure that all equipment is clean of dirt and fertilizer or any other debris. Equipment should be made of stainless steel or plastic. That way you avoid contaminating your sample with trace metals.
At approximately 5-10 locations within your property, take soil samples to a depth of 4" (lawn) or 8" (garden). Samples only need to be a spoonful or less. Each of the samples should come from the same soil type. Any soil that is VERY different in color or texture, should be tested separately. So avoid small areas where conditions are very different. Examples include: wet spots, natural areas, landscaped areas, etc. Mix all of the samples together thoroughly in the bucket. This will give you a composite sample to test.
Testing gives you precise information regarding the condition of your soil. With that information, you are able to:
Save money by purchasing only the fertilizer you need
Ensure that you are giving you lawn enough fertilizer to thrive
Protect nearby ponds and creeks from excess nutrients