Interpreting Your Soil Test Results for Lawns and Gardens

Published: March 7, 2016

Soil testing is an important tool for growing healthy lawns and gardens. To get reliable results and appropriate fertilizer and lime recommendations, it is important that you submit a representative soil sample from your lawn or garden. For guidelines in taking a representative sample and submitting to the lab for testing, visit MU Soil and Plant Testing Lab’s website at http://soilplantlab.missouri.edu/soil. Once the soil test is conducted and the results are available, the ability to interpret the results is an important consideration in correcting the deficiency or imbalance.

Example of Soil Test Report from MU Soil Testing Labs for Lawns and Garden Fertility Test:

Comments:
*** Fertilizer rates are given in pounds of actual nutrient per 1000 sq. ft to be applied
*** The soil needs additional organic matter for gardens and crops other than lawns. See MU Publication G6950, "Steps in Fertilizing Garden Soil" and G6956, "Making and Using Compost".
*** Lime takes two to three months to react with the soil. Apply lime three to six months before planting.
*** For blueberries soil needs to be treated with 50 lbs of elemental S per 1000 sq. ft to acidify the soil. It takes 3 months for S to react with the soil and acidify the soil.
--- The soil should be tested every 2 to 3 years to determine the effects of your fertilization practices and to develop a new set of fertilizer and limestone guidelines.

Explanation of Soil Test Report Form:

“Sample ID”: This is information you provided upon submitting your sample. The fertilizer suggestions are based on this.

“Ratings” indicates how high or low your soil is considered in each category.

“pHs” is an indication of the acidity or alkalinity of soil. A pH of 7 is neutral, while values below 7.0 are acidic and values above 7 are alkaline or basic. Vegetables and flowers grow best from pHs of 6.0 to 7.0. Most lawns grow well in pHs range of 5.5 -7.0. However, acid loving plants like azaleas, rhododendrons, blueberries and raspberries prefer pH below 5.5.

“Phosphorus, potassium, calcium, and magnesium” tests results are listed in lbs/a in the next four lines. These are some major essential elements required for plant growth. However, these numbers have little meanings for home owners. The ratings, however, indicate if these nutrients are considered low or high.

“Organic Matter” is the percent of organic matter found in your sample. Soil organic matter is essential in the formation of soil structure, reducing compaction, and for retaining plant nutrients. It helps in improving the water holding capacity of the soil, aeration, and tilth. While soil organic matter levels between 2% and 3% are fine for lawns, 4% to 6% is better for vegetables and flowers.

“Neutralizable Acidity (NA)” is a measurement of reserved acidity in soil and reported in mille- equivalents per 100 grams of soil (meq/100 g soil). This number along with pHs is used in calculating the lime requirement in soil.

Cation Exchange Capacity (CEC) is the ability of the soil to withhold positively charges nutrients and is reported in meq/100 g soil. While soils with high CEC values can retain more nutrients, low CEC soils can only retain fewer nutrients.

“Fertilizer and Limestone Recommendations” indicates how much nitrogen, phosphate, and potash (potassium), Zinc, Sulfur and lime your soil needs. This is the most important part of the report for home owners. These rates are in pounds needed per 1000 square feet. Depending on the garden size specific amount of nutrient requirements needs to be calculated and fertilizers to be selected accordingly.

“Comments” The soil test reports have comments at the end of the reports with notes on soil test in general, with additional notes for specific recommendations for your soil.