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Alkaline Soil

The pH reading for alkaline soil falls above 7 in a soil test result. Caused due to the presence of sodium carbonate and minerals in large amounts, this soil is treated with specific chemicals. This article explains what this soil is, what it's caused by, and the various treatments for it.
Gardenerdy Staff
In previous times, farmers tasted the soil to check its condition. With this simple trick, the farmer could easily conclude whether it was suitable for growing crops or not. Even though soil tasting is not a precise or safe method, it helps in quick evaluation of the soil. A sweet taste signifies near neutral soil pH, a sour taste means acidic soil, and a bitter taste is an indication of alkaline soil.

What is it?

The acidity and alkalinity of soil is tested by a simple technique called the soil pH test. It can be further divided into different types based on the procedures. The measurement of hydrogen ions in the soil sample is common. A reading of 7 on the soil pH scale indicates neutral soil, lower than 7 is acid soil, and higher than 7 is alkaline soil. As compared to other types of soil, a highly alkaline soil has less solubility and low infiltration capacity. Both these factors negatively affect the growth of plants.

What Causes it?

The main cause for soil alkalinity is the presence of sodium carbonate in high percentage. Other minerals that may be detected in high amounts are calcium, magnesium, and sodium. Generally, areas that receive low amounts of rainfall every year tend to have alkaline soil. This is because the mineral salts that contribute to the alkalinity tend to retain in the soil in the absence of water. Mostly caused due to natural processes, increased pH levels could be brought about by long-term cultivation. For example, using hard water for watering plants may lead to increased alkalinity.

Treatment

Just like water, sunlight and nutrients affect the overall growth of plants. Soil acidity or alkalinity plays an important role in a plant's life. A major gardening issue faced is reduced availability of some essential plant nutrients such as copper, iron, and magnesium to the plants growing in the area. In addition, the microorganisms in the soil responsible for breaking down the nutrients remain in a dormant state at higher pH levels, thus reducing soil fertility.

Neutral pH soil which is moist and well-drained is preferred for growing healthy plants. If your garden soil pH reading is high or alkaline, you have two main approaches for treating it: one is lowering the soil pH, which is not very easy, and the other option is growing plants that can survive in alkaline soil. Methods for correcting the soil involve supplementing it with chemicals like sulfur, aluminum sulfate, iron sulfate, manganese, or borax. However, this method requires close monitoring and soil pH tests at regular intervals until you get a near stabilized pH range.

Alkaline Soil Plants

There are a certain group of plants that thrive well in higher soil pH levels, i.e., within the alkaline range. Whether you are planning to grow flowers, vegetables, vines, shrubs, or trees, you will get a large variety. It is important to understand soil science and choose plants after checking their required growth conditions. A simpler option is to ask your local horticulturist about the list of plants that adapt in this soil. Some alkaline soil plants are:

Herbs and Vegetables
  • Goldencup
  • Kenilworth ivy
  • Goosefoot
  • Dandelions
  • Baby's breath
  • Japanese anemone
  • Persian rockcress
  • Sweet pea
  • Common bean
  • Chickweed
  • Queen Anne's lace
  • Hydrangeas
  • Chicory
  • Yams
  • Asparagus
  • Parsley
  • Okra
Shrubs and Trees
  • Japanese honeysuckle
  • Chilean jasmine
  • Daphniphyllum
  • Feathery cassia
  • Japanese quince
  • Heather
  • Littleleaf boxwood
  • Silverthorn
  • Cassina
  • Lavender
  • Holly oak
  • Japanese plum
  • Asian persimmon
  • Olive tree
  • Cedar elm
You can also consider organic amendments for alkaline soil. Effective choices are peat moss, sphagnum moss, and pine straw. These supplements will take a longer time for bringing down the garden soil pH to desirable levels, but they are better alternatives to using chemicals in garden soil.
Unripe persimmon & fresh green
Leaf and fruit of the Daphniphyllum
Asparagus plants
Yam planting
Blue chicory flowers
Hydrangea Macrophylla
Chickweed flowers close up
The stems of peas
white Flower
Quinoa plant
Kenilworth ivy or birdie, Cymbalaria muralis
Golden-cup St. John's Wort