Soil Test Results: "What's Next?" Guide for Homeowners

All too often, digesting the results of a soil test can be challenging, to say the least, due to the analytical nature and results that are given. To make it more daunting, an action plan must be made to improve the soil to achieve positive results and optimum plant health. This guide can help develop an action plan in three easy steps to improve soil in the landscape and make the right "What's Next?" decisions. Visit Agricultural Analytical Services Lab online or on Facebook to connect and learn more.

Step 1. Nutrient Levels: Correcting/Improving Soil pH

Soil pH is a measure of the active acidity or alkalinity in soil. Most turf and ornamentals prefer a pH of 6.0 to 7.5. Certain acid-loving plants prefer a pH less than 6.0. Refer to the diagram to understand and compare the specific pH results.  

Action Task: In order to increase pH, apply calcitic limestone. This is quite common! Limestone can be purchased from a local source and can be incorporated into the soil or applied with a granular spreader. In order to lower pH, apply or incorporate sulfur (less common). Rule of thumb: to increase the pH by 1.0, apply 40 pounds of lime per one thousand square feet. Fact: One acre is 43,560 square feet. Example: For one acre, 43 bags would be needed to increase pH by 1.0.

Step 2. Nutrient Levels: Correcting Nitrogen, Phosphorus, Potassium

Perhaps confusing areas on a soil test result are the recommendations for nitrogen (N), phosphorus (P), and potassium (K). All too often, the application rates that are suggested along with the corresponding surface areas can be overwhelming after the first review. Here's a simple explanation of N, P, K, and guide for next steps based on the results and recommendations. First, understand that these primary macronutrients are necessary for proper plant health. As a result, it is important to know their basic functions from a plant lens.

Nitrogen

• Most important component for promoting plant growth
• Nitrogen makes up part of the chlorophyll in plants (that's why they are green!)
• Gives plants energy to grow

Phosphorus

• Essential for growth and cell division
• Essential for root growth and development
• Required for seed and fruit development

Potassium

• Increases ability of plants to withstand stress
• Essential for development of a healthy root system
• Promotes photosynthesis

Now what? Action Task: After reviewing the recommendations for N-P-K, understand that several types of fertilizers may be needed to improve deficiencies. First, the nitrogen needed will be written in pounds per 100 square feet. (example: 3.5 pounds of 5-10-10 per 100 square feet).  Proper surface area will need to be taken into consideration to determine total amount of fertilizer needed.  Fertilizers can be incorporated into the soil or applied with a broadcast spreader on desired areas.

Fertilizers: Synthetic vs. Biosolids?

Biosolids are generally an environmentally friendly source of N-P-K nutrients (when applied at the recommended application rate), allowing the user to apply less synthetic N-P-K fertilizer to the soil. Biosolids are a safe, excellent source of organic material which can be used to enhance soil structure and increase a soil's water holding capacity. Biosolids contain significantly fewer pathogens than straight animal manure so they are generally a healthier organic fertilizer choice for turf, ornamentals, and vegetable gardens.

Step 3. Cation Exchange Capacity: Correct as Needed

Don't let this scientific term scare you! A soil's "CEC" is a calculated value used to determine the relative nutrient-holding capacity of the soil. The question is: How effective is the soil at delivering positive results to the plant? This is very important and is a powerful data point that should not be overlooked! While there is no "perfect" CEC value that fits every plant variety, climate, and soil type, soil CEC values typically range between 12-25 for most well-performing plants. Soils with CEC values below 12 are generally considered to be poor at holding nutrients and struggle to hold water, which could lead to drought stress. Soils with CEC values above 25 are generally considered "excellent" at holding nutrients in place.

Action Task: If the soil CEC is less than 15, incorporate one inch of organic matter into the top six inches of soil. Sources for organic matter include manure, biosolids, compost, or peat moss. These soil amendments can be sourced from a local store, landscape supply center, borough, township, or county facility.

Chart adapted from Purdue University, "Soils and Fertility"

Pulling it all Together

In order to achieve positive outcomes for plants, utilizing a soil test and understanding the results can be a vital piece of knowledge that can bring insights from a soil science perspective. This information will allow for proper decision-making and act as a springboard for thinking about yet more "Next Steps."