What is soil pH? Inshort, pH is a measure of the acidity of the soil and is based on a set of numbers from 1 to 14, universally recognized. It is a measure of the concentration of hydrogen ions in the soil solution. While the number 7 is the measure of the soil that is neutral, numbers above 7 indicate an alkaline soil and those below 7 are for acidic soil.
The Need to Lower Soil pH
Most plants grow best where the soil is slightly acidic, in the range of pH 6 to 7. While a few plants, such as azaleas, gardenias, and blueberries, grow best at lower pH levels, others such as centipede turf, camellias, and potatoes, grow well in a wide range of pH conditions, but seem to flourish in more acidic soils.
The other reason for lowering soil pH is its effect on the nutrient availability for plants. Soils with a pH of over 7.8, have a prevalence of iron, zinc, and phosphorus deficiencies. The high salt levels can lead to yellowing and poor growth of the plants.
The reason for high soil pH can be deemed to the arid climates, with the rainfall not leaching the calcium and other basic materials out of the soil, like the Black Belt prairie region of central Alabama. Sometimes, the high pH can be the result of gardeners inadvertently adding more lime to the soil than needed, without taking a soil test.
How You Can Lower Soil pH Level
The first step in lowering soil pH is to test the soil using a soil testing kit. There are two basic types of soil testing kits available. While one is a capsule that will change the color of the soil and water mixture, which is then viewed against a color-coded chart, the other is a fully reusable probe, with a simple-to-read meter at the top.
The next step includes the challenging and slow process of lowering the soil pH, using organic or inorganic soil amendments. Based on the pH, lime content, soil texture, and mineral and nutrient content, you can use any of the following methods to lower the soil pH.
➨ In the majority of the cases, soil pH can be lowered, simply by using fertilizers containing ammonium, like ammonium sulfate and sulfur-coated urea.
➨ You can also amend the soil by adding sulfur available in two forms, dusting sulfur and aluminum sulfate. Dusting sulfur may take several months but aluminum sulfate has an immediate effect. A costly but effective way to lower soil pH is using iron sulfate. While mixing sulfur, the soil must be moist, aerated and warm for fast bacteria growth.
➨ For those who prefer the more organic method, compost acts as a buffer to protect plants from unbalanced soil pH. You can use decayed vegetable matter, compost, stable manure, and straw to increase the acidity of the soil. This method allows the pH to be slowly lowered over time, while increasing microbial life and improving the structure of your soil.
It is important that before acidifying the soil, a gardener ascertains the reason as to why pH levels are high and the soil's type. A sandy soil would require less amendment than clay soil. Ensure that while applying the soil amendments, the correct amount of the product is added.
Soils that are over acidified should be limed to neutralize soil pH. Once the soil pH has been acidified to the desired level, it has to be monitored over time with regular sampling and soil analysis.