How to Understand pH In Your Garden Soil
In many gardening related articles you will be asked to adjust your soil pH to a certain range depending on the plant you are trying to grow. But what does pH really mean and what do I do with that information?
For plants to grow properly they need nutrients from two sources – nutrients from the atmosphere such as oxygen, carbon and hydrogen, and nutrients from the soil, such as nitrogen, phosphorus, sulfur and potassium (there are roughly 12 more nutrients that can be found in the soil).
pH relates to those nutrients and their availability in the soil.
pH is the numeric scale from 1 to 14 to measure the acidity or basicity (alkalinity) of a solution that contains water. Acidity is defined as anything lower than 7.0 and basicity is defined as anything above 7.0.
Under acidic conditions, many soil nutrients dissolve increasing the concentration of metal ions (such as aluminum, manganese and iron) to toxic levels which inhibit plant growth.
Under alkaline conditions, the solubility of minerals decrease causing nutrient deficiencies which also affect plant growth.
Our goal as gardeners is NOT just to manage soil pH levels but rather to make sure that there are no toxic metals in the soil and that nutrient availability is at its maximum – and that is usually achieved when soil pH is between 5.8-6.5. However, each plant requires a specific pH level - these are the required pH levels for each plant.
Many home gardeners do soil pH tests before the growing season to make sure their soil is at the required pH level. In fact soil test are done in a couple of locations in the garden because pH levels can vary even within your garden. Farmers conduct soil tests before, during and after the growing season so that optimal pH conditions are maintained throughout the growing season.
Soil pH can be adjusted depending on how acidic or how alkaline your soil is. In general limestone is used to raise pH level and sulfur is used to lower it. Howver, only precise pH analysis (by doing soil test) will tell you what needs to be done to properly adjust soil pH.