The lab will want to know what crop or ornamental plants are present or intended for the soil to be tested. It's important that your lab considers both what's lacking in your soil and the needs of your specific plants in making a fertilizer recommendation. Test your soil at least once a year. It's important to test each year to find out what changes have taken place in your soil's nutrient composition. Like pH, the organic matter content of your soil can influence whether or not nutrients are available to your plants.
Organic matter holds nutrients in the soil by reducing leaching.
It also preserves soil moisture, and lessens the potential for erosion and compaction. An ideal range for most soils is between 3 percent and 5 percent organic matter. Sandy soils will have less, and clay or silty soils may have more. Organic matter is continually being used up, including breaking down into nitrogen, sulfur and other elements taken up by plants. Vegetable and animal matter returned to the soil in the form of mulch, cover crops, crop residue or manure increases the soil's organic matter content.