Hard layer under sandy soil #732663 - Ask Extension

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Hard layer under sandy soil #732663

Asked October 30, 2020, 7:24 AM EDT

Hello! I have planted a persimmon tree in Wilmington and at the bottom of the hole I dug there was a layer of very hard brown soil which I think is old peat based on my Google depth of knowledge. It was about 30 inches down and I planted this young Rossyanken persimmon on top of it. It is keeping me awake at night worrying about it! That layer appears to be throughout my yard but should I find a way to break through it or dig the hole deeper? Thank you!

New Hanover County North Carolina

Expert Response

Hello,
Yes, we often refer to that soil as a hardpan. This type of soil compaction can lead to poor water infiltration, increased water runoff and soil erosion, restricted root growth, reduced nutrient uptake, and ultimately poor plant growth.  Hardpans do not allow water to drain so it oftentimes is a hole that holds water. Does water sit in this area after rain? If so how long?
One way to handle a drainage problem is to raise the height of the soil. Elevate the site by adding 10-12 inches of well-drained topsoil, compost, or other organic matter to raise the planting zone. The amendment should be tilled into the soil to provide a homogenous medium for the plants. The root zone of the tree is then adequately above any poor internal drainage. Otherwise, you would have to find a tree that can tolerate wet soils.  Be sure you till a large area for the tree and mulch around it.  At a minimum, the bed should be 3' x 3'.  You will want to plant the tree slightly higher or level with the ground.  If you dig the hole deeper I am afraid the tree will sink and then succumb to death from being planted too deep. 
As a last resort you can score the sides of the hole with a shovel.  This may help with drainage.  You could also do a little experiment.  Dig a 1' x 1' size hole and fill it with water.  Time how quickly it takes for it to completely drain.  If it is less than 12 hours the plant should be okay.  
Good luck,
Susan Brown 
Susan Brown Replied October 30, 2020, 9:34 AM EDT

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