The impact of Soil PH on your Lawn

Let’s begin with the basics. PH stands for Potential Hydrogen. This makes sense when you learn the PH of the soil is impacted positively or negatively by the amount of hydrogen (H+) ions it is holding. Some soils are naturally higher in H+ ions (Clay) and some soils are naturally lower in H+ (Sandy loam), which gives them a natural deviation from the neutral PH of 7.

The PH impact of a soil regulates its ability to pass nutrients stored in the soil to the plants growing in it. Not all nutrients are created equal and therefore nutrients flow through the soil at different rates based on the soils PH. When PH moves too far away from a neutral PH, the soil can “lock up” the nutrients (see exhibit 1), therefore starving the plant from critical nutrition. The goal of soil management is to move the soil PH to an appropriate level based on the plants that are growing in it. Plants such as blueberries like acidic soil between 4.5-5; where Daylilies prefer a PH of 8, home lawns prefer 6.0-6.5 PH. These plants grow best at these levels because the nutrient availability in the soil is optimal for them. Blueberries love iron and iron is highly available in 4.0-5.0 PH soils.

Adding calcitic lime to our lawns, gardens and natural areas has several positive impacts, one of which is adjusting the soil PH. Please note that lime does not create a permanent change to the soil PH, only organic amendments such as compost, biochar and increased soil biology can create a permanent change to the soils PH. Lime adds significant amounts of Calcium and Calcium Carbonate to the soil which attracts hydrogen (H+) ions and bonds with them, subsequently removing their impact in the soil and raising soil PH. Calcium is an essential macro nutrient for plants, but also plays a massive role in soil structure. Calcium ions position themselves between the soil platelets, like cartilage, inhibiting the platelets from collapsing while creating space within the soil for air, water, and nutrient movement. Calcium leaches from our soils through natural processes. When this happens and the calcium level in soil can become deficient and the soil collapses and becomes compacted.

In Charlotte, we have heavy clays which hold a lot of nutrients and readily uptake calcium and calcium carbonate into the soil. Providing your soil calcitic lime as part of your regular soil maintenance can greatly increase the nutrient availability within the soil, the soils structure and improve the effectiveness of any fertilizer additives. Lime is a slow-moving application (see exhibit 2) and therefore needs to be planned annually to ensure your soil is optimized for the growing season.