Official soil sampling kits from the LSU AgCenter.

Home Soil Testing

Barry from Avoyelles Parish again called AHA on behalf of a friend at his church who wanted to do his own soil testing on his own landscape. This friend wants to test many sites on his landscape and seems to be interesting in mapping his soil’s quality. By the way, our modern farmers do map their fields with respect to both crop yields and to soil quality.

AHA complied with the request and found some online consumer blogs rating the best tests on the garden markets and then shared them with Barry. However, AHA added the caveat that accuracy of testing soils at home is uncertain.

Later AHA looked for conclusive information about the advantages and disadvantages of home testing of soil, and he found some useful online information from extension professionals at Montana State University and at the University of New Hampshire. Both extension webpages shared a couple of conclusions:

1. Results from home testing tend to be less accurate than results from a professional laboratory.
2. Some testing kits are very inexpensive but yield inaccurate results. Expensive kits produce more accurate results.
3. The results from home testing fail to make recommendations with regards to both liming and to fertility.

Soil sampling kits are available at local AgCenter office, and some garden centers will have these kits. These kits go to a professional test lab at the LSU AgCenter, and a gardener will usually receive test results with rates and formulations for lime and for fertilizer in one business week.

An azalea with fungal leaf spot. Photo: Melissa Harris, LaSalle Parish.

Azalea Leaf Spot

Melissa from LaSalle Parish emailed AHA with a picture of an azalea with leaf spots, “Can you ID what might be going on with these azaleas? They are in a home landscape and are 15-20 years old. Thank you!!”

Melissa has fungal leaf spots on her azalea. Several AgCenter articles mention using fungicidal sprays to prevent these infections, but these sprays fail to cure the infection once it is observed.

However, a gardener can use a fungicidal soil drench, an easier method of application than spraying. The process entails mixing the fungicide, per label directions, in a bucket and then pour the fungicidal solution around the base of the azalea. This treatment can be used for other ornamental plants for fungal protection and would be systemic and last longer than a spray.

The disadvantage of a drench would be the lag time because the plant will take of the fungicide through its roots and then the treatment will spread in the plant.

Here are products labeled for fungicidal soil drenching:

• Bayer Advance All-in-One Rose and Flower Care™
• Bonide Rose Rx Systemic Drench™
• Bonide Infuse Systemic Disease Lawn & Landscape™
• Ferti-Lome Halt Systemic Rose, Flower, Lawn Ornamental Fungicide™
• SA-50 Thiomyl Turf and Ornamental Systemic Fungicide™.

Again, always read and follow label instructions for safe and effective pesticide treatments.

A line from the results of a soil test. Image: Cindy Sakovich, DeRidder, LA.

Low Magnesium

Cindy sent an email with her soil test results, “Here is the soil sample. Do I need to add magnesium?”

Cindy’s analysis also had a pH of 5.35, a low level, for which liming can fix. Dr. Mary Helen Ferguson, an AgCenter horticulture agent, in her blog about fertilizers shares this recommendation, “When magnesium (Mg) is needed in the soil and soil pH is low, using dolomitic lime [or “mag” lime] – or lime that contains both magnesium carbonate and calcium carbonate – kills two birds with one stone. Dolomitic lime is generally 6 to 12% Mg.”

Carrot seedlings with a high germination rate. Photo: George Giltner, Advanced Master Gardener.

Successful Seed Germination

George, an Advanced Master Gardener, shared another success story about his vegetable seedlings, “This is a pot of carrots germinated in Garden Magic™ garden soil/compost with superior germination rate. The top coating is sand. I think the good results are from using an excellent compost with plenty of air spaces – aerobic [high oxygen] conditions. Also, the white object behind is a filter and dehumidifier. Compressed compost may lead to anaerobic [low oxygen] conditions that favor [disease] pathogens.

“I have the same great germination with pots of beets, radish, lettuce, and turnips, but they are grown in greenhouse conditions without freezes, wet days, and low humidity and extended/higher intensity lighting and air circulation.”