When you get a soil test, you should specify the plants you want to grow. Then they give recommendations on what you should do. The most important things with rhododendrons and azaleas is drainage and acidity. Acidity should be around a pH of 5.5 to 6.

From: http://cnal.cals.cornell.edu/faqs/index.html#3

Does Cornell offer fertilizer recommendations?

Yes, Cornell provides nutrient recommendations for commercial farmers and home gardeners but the laboratory analyses are conducted by Agro-One. Samples and payment should be submitted directly to Agro-One. Questions about the nutrient recommendations should be brought to the attention of your local Cornell Cooperative Extension office or crop consultant.

Here is a link that might be useful: http://cnal.cals.cornell.edu/faqs/index.html#3

Here's a photo of my test results.

Beside being low in phosphorus, it looks like my major issue is high pH. If I do the math on the N-P-K requirements, it comes out to only about 1/10 of an ounce of each for a 4 square foot area, which would be the area where my azalea is planted. I also have some Espoma soil acidifier which is 30% sulfer......18% combined, and 12% free. How much of this should I add to the soil around the plant? The instructions call for 2 1/2 cups.

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Rhododendrons and azaleas are members of the Ericaceae, or "lime-hating" plants. They are commonly called acid loving, but they can't tolerate too much acidity any better then alkaline soil. These plants typically want a pH between 5 and 6.

Your pH is 7.3 which is alkaline (not acidic). Hence the lime recommendation is zero. If you want to grow rhododendrons and azaleas you could alter the pH with powdered sulfur. Your report doesn't say this but a Clemson Extension report (http://hubcap.clemson.edu/%7eblpprt/lowerpH.html) recommends using 4.0 pounds of elemental sulfur per 100 square feet in your situation. This is 1.5 tablespoons per square foot.

Your Espoma Soil Acidifier is elemental sulfur and gypsum. This is a good product for rhododendrons and azaleas. Since it is only effectively 20% sulfur, you would need to use 5 times as much of this as powdered sulfur or 20 pounds per 100 square feet. I can't give a tablespoon equivalent since the percent numbers are based on weight and not volume.

Your magnesium levels are good which is beneficial.

Your nitrogen levels aren't stated, but the recommendation is fairly normal since Nitrogen must be added periodically. With rhododendrons and azaleas, nitrogen is obtained by replentishing the organic mulch periodically. Since you are building up the soil, don't use any nitrate fertilizer. Nitrates are common in nitrogen fertilizer but suppress Mycorrhizae which are fungi that help the roots take in nutrients, especially phosphorus which your soil is sadly deficient in.

Your potassium levels are normal.

Your phosphorus levels are very low. Rhododendrons and azaelas require normal levels of phosphorus for general health and flower production. Fortunately phosphorus levels can be raised with rock phosphate.

The N-P-K levels on fertizers are percent by weight. So 20 pounds of 5-10-5 fertilizer is 1 pound nitrogen, 2 pounds of phosphorus, and 1 pound of potassium. 20 pounds of 5-10-5 fertilizer per 1000 square feet would be ideal, or 2 pounds per 100 square feet.

Espoma's Holly-Tone fertilizer is a good rhododendron and azaleas fertilizer, but it is only a 4-3-4 fertilizer. You would need to augment it with phosphorus. You could use 25 pounds of Holly-Tone per 1000 square feet, or 2.5 pounds per 100 square feet AND 30 pounds of Espoma Rock Phosphate per 1000 square foot or 3 pounds per 100 square foot.

Alternatively you could use a raised bed. This is much easier to manage since it is independent of the native soil underneath. In areas with alkaline soil, this is the most common way to go. When preparing a raised bed use good garden soil mixed with conifer bark dust and peat moss to get a good acidic soil with lots of organic matter and good drainage.

Another worry, if your soil is alkaline, is your water alkaline also. If it is, then you best irrigate with rain water. This can be accomplished by collecting rain water from downspouts from a roof.

I hope this helps.

Here is a link that might be useful: How to grow rhododendrons and azaleas.

rhodyman, thanks! I had about 3 pounds of the Espoma Soil Acidifer left in the bag, so I just mixed it into a plie of double ground pine bark that I had, and used it for a mulch around the azalea, and also a hydrangea, which was also doing poorly. I also added a little balanced fertilizer into the mix. I don't do much watering by hand, but if I do, I add vinegar. Our rain water has a pH of 6.4. Thanks again for your help and suggestions. I'll let you know what happens. Ed