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soil amendments atlanta commercial landscapeIt’s that time of year again in north Georgia: The temperatures are warming; flowers are blooming; birds are chirping. It’s time for springtime landscape installations, and for many involved in landscape maintenance, that means time for soil amendments.

Common assumption holds that our red Georgia clay is horrible for landscaping, so we amend the soil. And if some amendment is good, then more is better — right? Well, if you’ve ever dug a hole, put in a plant and backfilled the hole with nothing but soil amendment, you’ve probably noticed it didn’t yield great results. After a few weeks, plants start declining. So what gives?

Georgia Soil Isn’t As Bad As You Think

soil amendment atlanta commercial landscapeFirst, let’s clear up the assumptions about our native soil: Georgia soils are actually pretty good for gardening. Clay soils have higher nutrient- and water-holding capacities than other soil types — in fact, the only soil type that has higher nutrient holding capacity are organic soils, which drain very well.

That’s why Georgia topsoil is so important: High concentrations of organic material provide high nutrient-holding capacity and good drainage. (It’s also where the bulk of plant roots are.) Clay soils have the smallest soil particles, which helps them hold nutrients and water — but they also work against us because they’re easily compacted, making it difficult for water to move through. Georgia clay soils are also composed of mostly minerals with very few organics.

Most developed sites have the topsoil layer completely removed and are compacted from heavy construction equipment, resulting in poor drainage and stifled roots.

So we amend the soil to improve it — but there are wrong and right ways to do this.

Soil Amendments: The Wrong Way

The most common (and also the least expensive) way to amend soil is “pocket planting.”

All too often, people mix too much amendment in the backfill or backfill with straight amendment. This can lead to two problems”

  • The amended soil around the root ball is more porous, soaking up water like a sponge, which can actually create a bathtub effect that results in root rot, ultimately killing the new plant.

  • The new roots can actually end up growing in circles in the new planting pit. Over time the circling roots can strangle the plant and lead to decline or death.

When pocket planting, dig a hole twice as wide as the root ball and mix soil amendment in with the native soil. Then, backfill the hole with the amended native soil — about 25 percent amendment to 75 percent native soil.

Soil Amendments: The Right Way

The best way to amend new plants is to amend the entire planting bed.

Put down 3 inches of amendment down and till it into a depth of 12 inches. (Avoid tilling near existing tree roots, as the process can damage trees.)

Tilling the amendment all the way through the soil profile creates a uniform soil layer with increased nutrient holding capacity — but it doesn’t cause drainage issues like pocket planting can.

This process mimics the topsoil layer found on an undisturbed site.

Not All Soil Amendments Are Created Equal

When selecting a soil amendment it’s important to recognize that not all soil amendments are created equal. Some can actually be detrimental to new plants.

A good soil amendment should increase organic matter in the soil profile and improve soil drainage. However, it is important to make sure the organic material is highly composted. Otherwise the microbes that break down the compost can actually steal the nitrogen in the soil from your new plants.

Let HighGrove Help!

We’ve established that there’s a wrong way and a right way to amend your soil — but the best way to amend your soil is to rely on the professionals to get the job done right. Start the process by contacting HighGrove Partners about a soil assessment and consultation for your Atlanta commercial property.

Call us at 678-298-0550, or fill out the form to the right to schedule your complimentary consultation. For more Atlanta commercial landscape insights, subscribe to the HighGrove blog.

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Last modified: March 20, 2014