Using Sampling and Testing to Prescribe Fertilization

Soil and foliar sampling are great tools for understanding a tree’s health. Soil sampling will determine the nutrient content of the soil. Foliar sampling will show which nutrients the plant absorbs and the quantity. Accurate metrics allow arborists to determine how to address plant deficiencies or health.

The Soil Sampling Process

Soil sampling can be at a specific location, such as your backyard, or over larger areas, such as crop fields. The size of the plot and the degree of tests will determine the number of samples collected. For most homeowners, 4-7 samples should suffice. The soil is taken from various depths, mixed in a container, bagged, and labeled using a soil probe or spade.

The samples are then taken to a laboratory, weighed and dried in an oven, measured and weighed again depending on the test, and then tested with physical and chemical means. The results are then recorded. Some standard soil tests include:

• pH levels

• Organic matter content

• Chemical testing for nutrients

• Cation Exchange Capacity (CEC)

• Moister content to determine how well the soil drains

The soil analysis report above provides valuable insight. In this report, the macronutrients nitrogen (N), potassium (P), and phosphorus (K) were deficient. The report includes a fertilizing concentration recommendation and the application rate per acre. These analyses can pinpoint corrective actions if your solid has nutrient deficiencies.

How Foliar Analysis Works

Foliar sampling analyzes plants to determine which nutrients they can access. As with soil, foliar sampling methods vary depending on the reasons for sampling. Agricultural sampling can consist of hundreds of samples taken over acres of crops. Single tree samples taken for plant nutrient levels can be sample sizes of a single tree. The plant tissue is again collected, bagged, and labeled. Common reasons for foliar testing include:

• Determine current nutrient levels and fertilizing needs

• Determine levels of metal in the foliar tissue

• Determine the bioavailability of nutrients in the soil

The sample analysis identifies the levels of macro and micronutrients that plants need to thrive. The bar graph allows a quick interpretation of which nutrients are deficient, abundant, and absent. Combined with a soil analysis, this helps determine how much of the available nutrients the plant can absorb. Besides knowing which metals are present in a plant’s tissue, foliar analysis determines fertilizing needs beyond a standard soil analysis.

Is Testing Right For My Tree?

In conclusion, soil and foliar sampling give us insight into the soil’s nutrients. These insights also provide scientific guidance when making fertilization recommendations. If you would like a soil analysis, contact us for a consultation. We will collect, analyze, and interpret the results so you can make science-based tree care decisions!