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Garden Soil pH Testing Methods, Techniques, Ideas

Garden Soil pH Testing Methods

Let us discuss today the garden soil pH testing procedure. Let us get into  Garden soil pH testing methods, techniques, and ideas: As home gardeners, you must have come across a common suggestion to test for your garden’s soil pH and grow plants accordingly soil pH is one of the key factors that that affects the growth and productivity of your garden. Plants can access nutrients from the soil only if the soil pH is within a favorable range. If the soil is outside of that range, when if you can add all the fertilizer that your plants desire and it will never make it into your plants. Our gardener friends often write us about problems they face while raising their home gardens, like the appearance of yellowish green foliage due to iron deficiencies triggered due to the alkalinity of garden soil as iron is readily available to plants in 5 to 6.5 range of soil pH. Garden soils are usually described as acidic or alkaline but the meaning of these terms and their relationship with the plant growth is not clearly understood by some gardeners and unfortunately, they end up choosing wrong plants for soil with different pH levels.

So, today as promised we have another stock of information for successful home gardening, we will discuss what is soil pH and Easy pH testing methods for garden soil.

Every home gardener must have knowledge about garden soil pH testing methods for successful gardening.

What is soil pH?

pH simply stands for “potential of hydrogen”, in chemistry it is often defined as, the negative common logarithm of the activity of hydrogen ion in solution mathematically written as  pH= ─Log(H⁺). In simple words, we can define pH as, a measure of the relationship of hydrogen ions (H⁺) to hydroxyl ions (OH). It is a mathematical expression to measure the number of hydrogen ions present in the soil. For a gardener’s purpose, pH indicates how acidic or alkaline the soil is. The pH measurement is a logarithmic scale that varies from 1 to 14. Something with a pH of less than 7 is acidic; 7 is neutral and anything higher than 7 is grouped as alkaline. Because it is a logarithmic scale, each value increases by 10 times. For instance, a pH of 8 is 10 times more alkaline than a pH of 7. For the home gardening needs, it is sufficient to know whether your soil is alkaline or acidic for the reason that certain nutrients can only be accessed by plants when the soil pH falls into an acceptable range and no amount of fertilizer can improve plant’s health until the soil pH has adjusted.

Read: How to Grow Carrots in Pots.

 Role of soil pH in home gardening:

Generally speaking, when taking round in your home garden if your plants are growing healthy, with no signs of serious problems then your soil pH is probably in an acceptable range. However if your plants are looking stressed, discolored, or not growing vigorously, one of the primary thing you should do is test your soil pH.

Your garden soil’s pH can have a deep effect on what nutrients are available to your plants. This is especially significant for those who prefer using synthetic fertilizers to feed your crops. If you are already using compost and working with manures you might find the pH of your soil adjusting to perfection without your efforts. Knowing your soil pH is the key to understand if essential minerals will be readily available to the hungry roots of your plants. Most of the plants thrive best in neutral soil or in soil that is slightly acidic. If your soil is acidic or too alkaline, then your plants will not grow to their full potential.

The good news is, in spite of what soil your plants are growing in, you can always modify the soil pH level so that your plants can thrive. Another choice is to select plants that you know will thrive best in the soil that you already have. While most plants can adapt to any soil pH in the neutral range of 6.0 to 7.5, some plants have distinct preferences such as Blueberries and Azaleas prefer very acidic soil, and Lilacs and Clematis can grow in more alkaline soil.

Soil Acidity:

The lower the pH of the soil, the greater will be the acidity. Soil pH should be maintained at above 5.5 in the topsoil and about 4.8 in the subsurface. In broad-spectrum soil, acidity is a major environmental and economic concern. If remains untreated, acidity will become a problem in the subsurface soils, acidic soils cause significant losses in production and the choice of the plant will be restricted to acid-tolerant species and varieties hence opportunities to grow a variety of crop may be reduced.

Effects of soil acidity

Plant growth and most soil reactions, including nutrient availability and microbial activity, are favored by soil with a pH range of 5.5 – 8.

Acid soil, chiefly in the subsurface also restricts root access to water and nutrients.

Aluminum toxicity
  • When soil pH drops, aluminum becomes soluble. A small drop in pH can result in a large increase in soluble aluminum. In this form, aluminum retards root growth, restricting access to water and nutrients.
  • Poor crop and pasture growth, yield reduction and stunted growth as a result of inadequate water and nutrition.
Nutrient availability

In very acid soils, all the major plant nutrients (nitrogen, phosphorus, potassium, sulfur, calcium, manganese and also the trace element molybdenum) may be unavailable, or if available will be in inadequate quantities. Plants can show deficiency symptoms despite ample fertilizer application.

Microbial activity

Low pH in topsoil may influence microbial activity, most notably decreasing legume nodulation. The resulting nitrogen deficiency may be indicated by reddening of stems and petioles or yellowing and death of oldest leaves on grain legumes.

Causes of soil acidity

Soil acidifies because of the concentration of hydrogen ions in the soil increases. The main cause of soil acidification is an inefficient use of nitrogen, followed by the export of alkalinity in produce.

Ammonium-based fertilizers are major contributors to soil acidification. Ammonium nitrogen is readily converted to nitrate and hydrogen ions in the soil. If nitrate is not taken up by plants, it can leach away from the root zone leaving behind hydrogen ions thereby increasing soil acidity.

Read: Garden Mulching Process.

Management of acidic soils

  • Soil testing: Knowledge of how soil pH profiles and acidification rates vary across the garden will assist in effective soil acidity management.
  • Liming: Liming is the most economical method of managing soil acidity. The amount of lime required will depend on the soil pH profile, lime quality, soil type, farming system, and rainfall.
  • Complementary management strategies: If soil pH is low, using tolerant species/varieties of crops and pasture can reduce the impact of soil acidity. Although this is not a stable solution because the soil will continue to acidify without liming treatment.
  • A number of management practices can reduce the rate of soil acidification. Management of nitrogen fertilizer input to reduce nitrate leaching is most important in high rainfall areas.

Alkaline Soil

If you live in an area that has little rain throughout the year, coupled with heavy clay soil, there is a bright possibility to have a highly alkaline garden.

  • Zinc and Copper Deficiencies

The elements zinc and copper play great roles in plant metabolism but are markedly scarce in alkaline soils. Zinc is a key nutrient that forms chloroplasts for photosynthesis. Deficiencies causes delayed or stunted vegetative growth. During the summers, lack of copper within the soil is evident across the plant’s leaves and stems; copper is a must have for proper metabolism especially for plant enzyme production. Leaves and shoot tips become stunted and scorched as the plant shows signs of dieback.

  • Iron Deficiency

Iron is a chief element required for chlorophyll, it is one micronutrient that should be available to plants on a constant basis. Without a proper supply of iron in alkaline soils, the plant cannot absorb the sun’s energy for the plant’s food production. Iron deficiency manifest as leaf chlorosis in which green foliage turns pale and yellow. If the deficiency continues, the whole plant succumbs to dieback since it cannot photosynthesize for energy and food. 

  • Manganese Deficiency

Also used in chlorophyll synthesis and functioning, manganese is another important micronutrient. Its reduction in alkaline soils also contributes to chlorosis in plants. Some plants may exhibit gray stripes or spots across the leaf structures as a result of low manganese concentration.

  • Presence of excess salts in the soil retards the germination of seeds and growth of seedlings. Plants die before bearing fruits.
  • Alkali salts in the soil also affect the plant growth by reducing the size of leaves in alkali soil, plant roots remain superficial, and the bark of stem turns brown or black, green tissues are less developed.

Factors which make the soils alkaline:

These are:

  1. Poor drainage in an arid region,
  2. Rapid evaporation of alkaline soil solution, and
  3. Excess uptake of alkaline salts and little percolation.

Management of alkali soils:

Chemical method: Application of calcium sulfate (gypsum) in the soil reduces alkalinity to a great extent and makes the soil fertile.

Mechanical practices such as improving drainage and leaching, the mechanical shattering of clay pans, and scrapping. The alkali salts are removed by:

(1) Scraper or by rapidly moving streams of water,

(2) Deep plowing of the land which reduces the alkalinity and makes the soil more permeable.

(3) Application of green manures has been found most successful in the reclamation of alkali and saline soils.

(4) Spreading of straw and dried grasses and leaves on the alkaline soil.

(C) Cultural method (growing salt tolerant plants) Some plants are resistant to alkali salts such as Barley, wheat, oats, grapes, and sugar-beet is best suited to grow in alkaline soil.

In India, Dr. Neel Ratan Dhar (1935) succeeded in reducing the alkalinity of the soil with the application of molasses and press-mud. The molasses is fermented by soil microbes and as a result of fermentation organic acids are produced which lower the alkalinity and increase the availability of phosphates and other important salts. The press- mud contains Ca which forms calcium salts that reduce the content of exchangeable sodium. Phosphate helps in the microbial fixation of nitrogen into nitrogenous compounds in the soil which ultimately fixes fertility of the soil.

How to test garden soil pH at home: easy ideas

You have some easy options when it comes to testing your soil’s pH. There are many do-it-yourself testing kits available in local garden centers and you can easily locate soil testing laboratories for more precise and reliable results. But here are few do-it-yourself ideas for testing soil pH

Materials required:
  • A handful of gardens soil without any plant material twigs or leaves
  • Garden spade or shovel
  • Bucket to mix soil
  • 2 containers
  • Measuring cup
  • Tablespoon
  • White vinegar
  • Distilled water
  • Baking soda
  • pH test strips, also recognized as litmus paper
Step 1: Collecting Soil Samples

A flat spade works greatly for the collection of soil samples.  Scooping out soil from only the top layer will not give you a precise result.  You need to get soil exactly from where the roots of your plants will be getting nutrients.  According to your preference, each location can be tested separately. To get a good sample, dig down at least 6-8 inches and make a hole. Now position the spade 2 inches back from the opening and go down to the depth of the hole.  Obtain about a ½ cup soil from the length of the spade.  This is the soil that you will use as your soil sample.

Put the sample into the bucket or container that you will be using.  Do this in several different areas of your garden and then mix the samples together well for eliminating any error due to biasness of area.

Step 2: Testing the Soil

Testing for Alkalinity

  1. Take a soil sample from 4 to 6 inches below the surface of your garden. If you have a small garden, you can mix soil from three or four different samples from different locations. If you own a large or a spread out garden, it is preferred to test several samples separately.
  2. Remove stones, twigs, or other foreign debris from the soil, and break up any large soil clumps.
  3. Put about 1 cup of soil into a clear glass container.
  4. Add enough water to turn the soil into mud.
  5. Add 1/2 cup of vinegar and stir slightly.

If you observe fizzes, foams, or bubbles, your soil is alkaline. If not, you can test it for acidity.

Testing for Acidity
  1. Take a soil sample from 4 to 6 inches below the surface of your garden. Do not attempt this second test on the soil you poured vinegar on.
  2. Remove stones, twigs, leaves, or other foreign debris from the soil, and break up any large clumps.
  3. Put about 1 cup of soil into a clear and clean glass container.
  4. Add an adequate amount of water to turn the soil to mud.
  5. Add a 1/2 cup of baking soda and stir.

Another rather easy method for testing soil pH is using litmus paper test

To get an actual pH measurement of the soil you can use pH test strips, also known as litmus paper, with the full range of readings from 1.0 to 14.0.   For this mix, some of your soil with distilled water until it is the consistency is like a milkshake wait until the soil particles settle. Once the liquid clears, put a strip in the mixture for about 20-30 seconds, and then dip in distilled water to clean off the mud.  Now compare the color of the strip with the color codes furnished with the test strips where its color indicates the pH.

How to correct  garden soil pH

It takes time to change the pH of the soil, often months, and it will need to be a consistent process. Left alone, the soil will sooner or later revert back to its natural pH. However, you won’t have to adjust all your soil, except it is extremely acidic or alkaline. You can regulate the areas where you are growing plants that need a different pH.

Mainly, the pH of acidic soil is raised by the addition of lime. While the pH of alkaline soil is lowered by adding some form of sulfur. How much to amount is to be added depends on current soil pH, the texture of soil (clay, sand, loam) and what you will be growing.

Once you have brought your soil pH into an acceptable range, you will need to reapply either lime or sulfur on a regular basis, to keep it there. This is best done in the offseason, so that the amendment has time to work its way into the soil slowly, without harming plant roots. It’s also a good idea to re-evaluate your soil about every 3 years, to see if adjustments have to be made.

That’s all folks about garden soil pH testing procedure.

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