Over that last several decades, university researchers have studied how soil conditions affect the growth of many different kinds of plants. The result is a collection of information about the optimum soil pH and nutrient levels required by many different plants. This information should be properly regarded as approximate, rather than definite, since soil is too complex to be characterized with precision.
Aspects of Soil Fertility
Most garden plants grow well when the pH of the soil is in the neighborhood of 6.2 to 6.6. There are a few garden plants that thrive at a lower pH, such as, potatoes, strawberries and raspberries. A partial list of recommended pH's is shown below.
Nitrogen, phosphorus and potassium
The macronutrients are used in large quantities by plants, and they are most often supplemented. Nitrogen require special attention since it is readily leached from the soil by percolating rain water. Typically, nitrogen fertilizer is applied every year as a matter of standard practice.
Calcium, magnesium and sulfur
The secondary nutrients are required in smaller amounts than the macronutrients, and they need to be supplemented less often. Any deficiencies can be addressed by amending the soil with lime, dolomitic lime or gypsum.
Deficiencies in boron, iron, manganese, copper or zinc are uncommon and problems generally only occur in areas with unusual soil conditions.
Organic matter improves the soil's water- and nutrient-holding capacity, and improves the soil texture. It also acts as a slow-release reservoir of nutrients. High levels of organic matter can reduce or eliminate the need for artificial fertilizers. However, excessive organic matter can lead to excessive amounts of nitrogen being released into the soil. This can lead to increased vegetative growth in plants such as tomato, at the expense of fruit production.
Using the Soil Test Report
The garden soil test report is customized based on the garden crop(s) you choose on the sample submission form. A graph shows how the level of each nutrient in your soil measures up to the recommendations for your crop. The quantities of lime and fertilizer required per 100 square feet of garden area are also reported. Please note that lime reacts slowly and it may take 6 months to a year for pH to reach the target level. An additional page of information is included that describes how to correct any soil problems identified.