How Alkaline Level Affects Plant Growth
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Testing Alkalinity
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The alkaline level in garden soil plays a crucial role in how well plants grow. It regulates the availability of vital nutrients that many plants need to thrive. It also can inhibit, or encourage, plants' ability to absorb those nutrients.
Alkalinity and acidity levels in soil are measured on a pH (potential of hydrogen) scale of 1 to 14. Soils with pH levels of 7.5 or higher are considered to have elevated alkaline levels. Soils with pH levels of 5.5 or lower are deemed acidic.
Soil pH
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Too much alkaline content in soil prevents vital nutrients from dissolving enough for plants to fully absorb them. Gardeners who can maintain alkaline levels in a moderate (6.0 to 7.5 pH) range can expect positive growth results. All other sun and moisture needs still apply.
Some flowering shrubs, like azaleas and rhododendrons, grow best in acidic soils, and will not fare well with high alkalinity. Most annuals, perennials, fruits and vegetables will grow better in soil with a moderate pH level that encourages absorption of key nutrients and allows plants to absorb them freely.
Some soils may require amendments such as sulfur (if pH levels are 8.0 or higher) or lime (if the soil's pH is 5.5 or lower). -
Soil pH and Nutrients
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Garden soil with elevated alkaline content can deprive plants of: the nitrogen needed to help green growth; the phosphorous that helps plants mature; the potassium that promotes health; the calcium that strengthens plant cells; the sulfur that builds immunities; the copper and boron that promote propogation; and the zinc that regulates plants' appetites. Highly alkaline soil can deplete its nutrient supply, and deficient alkaline content clogs the soil with more nutrients than plants can consume. Composted plant matter helps stabilize soil's alkaline content over the long term. However, changing pH levels in garden soil too quickly can do more harm than good.
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- Photo Credit flickr/diytinkerguy
