Pine bark can be used as a soil conditioner. I use it in all my containers.
"Pine Bark Benefits
Commercial pine bark products are usually made from the byproducts of milled wood. Finely ground pine bark works well as a soil conditioner because it helps the soil retain moisture, and adds “pore space” into the soil, through which oxygen and nutrients can filter. Pine bark soil conditioner also adds nutrients, such as sources of nitrogen, potassium, phosphorous, iron, magnesium and other minerals to the soil. Pine bark can be acidic, so if you use a large amount as a soil amendment or regularly apply it in your garden, you should monitor pH levels so that they do not fall below the desired level for the plants you’re growing."
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