Soil testing and examining the soil is crucial to growing healthy plants. Quite simply, plants won’t survive without good, healthy soil. Good soil can support plant growth because it contains the right amounts of nutrients plants need. Also, healthy soil has the right consistency to support root health and development. When the roots are growing rapidly, healthily, and happily, you can grow the healthiest plants.
That’s why soil testing is so important. Soil testing is checking for all the qualities of good soil: structure, compaction, ease of use or workability, the presence of natural organisms, plant development, water infiltration, and soil pH.
Here are some practical soil testing techniques.
Soil Testing for Structure
You can’t tell if your garden soil is dry or wet just by looking at the surface. Dig a small hole about 10 inches deep and place the soil in a small tray. Try to take an intact soil sample and break it apart with your hands. Check if the soil is granular, dry, cloddy, or powdery.
Healthy soil should contain crumbs of different kinds that can hold shape even when slight pressure is applied. If you need to use a lot of pressure to break soil apart, your garden soil is very hard. (And that’s not good.)
Soil needs to be porous and just the right consistency so that water can freely move through it. Also, oxygen, which is required by plant roots, will be able to reach the roots when soil is porous or well-aerated.
Checking for Soil Compaction
Very compact soil can significantly affect the growth of roots. The delicate roots won’t grow freely and anchor the plant in place in compact soil. Also, water and natural organisms such as earthworms won’t push through if the soil is too compacted.
To test for compacted soil, use wire flags. Plunge the wire in different areas of the soil. Check the depth until the wire starts to bend. If the wire bends early, then the soil is very compact. The ideal depth of the non-compacted soil is about one foot from the surface.
Soil Testing for Overall Soil Workability
Another part of soil testing is checking to see how workable the soil is. Workable garden soil allows water to efficiently move through to a plant’s roots. Also, workable soil is not susceptible to compaction. If the soil is not workable, then a lot of problems can show up later.
To test for soil workability, dig or till the soil using a small hand-held rake. If you produce plate-like soil clumps or cloddy dirt, then your soil has low workability. In extensive scale farming, farmers judge the soil’s workability by the amount of fuel that their tractors use. So, if you have to really work at digging the soil when using a hand tool, then the soil workability needs to be improved. Try mixing some organic compost into the soil.
The Presence of Natural Soil Organisms
Natural organisms—such as earthworms, invertebrates, and fungi—thrive in healthy soil. These organisms are very useful in fertilizing soil, and they can also help aerate it. Earthworm castings also help provide soils with organic matter, nutrients, bacteria, and enzymes. To test for natural organisms’ presence, make random visual checks on your garden soil.
Dig at least 8 inches deep, remove the soil and place it on a tray. Count the number of organisms you find. Use a stick to probe the soil particles. If you count more than 10 or 15, your soil is healthy. If you find less than 10, you may need to fortify your soil with compost.
To examine for earthworms, dig around 6 inches deep and count the earthworms you see. Three to five means you have good soil. No earthworms probably means your soil has little organic matter for earthworms to eat.
Note: If you live in a place where the climate is hot, then don’t expect to find earthworms near the soil surface. These creatures prefer cooler soils, so they tend to dig deeper into hot soils.
Checking For Plant Health and Vigor
An easy way to test for soil health is to check the overall health and development of plants growing in it. Look for uniform plant health, size, and color. For flowering plants such as the Top 10 Roses, flower production is a great way to monitor the health of the plants.
Healthy and vigorous plants indicate that the soil has good structure, good water retention, drainage, and a good population of helpful organisms. Having healthy plants also means that the roots are well-developed and are receiving the water and nutrients they need from the healthy soil.
Soil Testing to Evaluate Water Infiltration
Good soil must allow water to enter the surface and move through it. Excess water can drain out quickly. To test for water infiltration, water the ground until you have a small pool on the surface. Check the time it takes for the soil to absorb the water. Usually, it only takes a few minutes for healthy soil to absorb a pool of water, leaving the ground moist. If it takes more than 30 minutes, then the soil may be compacted.
Another way to test water infiltration is to use an empty can with the top and the bottom removed. Push this can cylinder through the soil until only a few inches of the body is above the surface. Fill the exposed part of the can with water and check the absorption rate. If only one-half to one inch of water per hour absorbs into the soil, your soil is compacted and needs to be amended.
Soil Testing for pH Level
A pH soil testing kit measures the acidity of the soil. Most plants grow best in a pH range from 6.0 to 7.5. (That’s why most commercial garden soils fall into that pH range. A soil pH of 7.0 is considered neutral–neither acidic nor alkaline.) Some plants prefer acidic soil. Blueberries, for example, like to grow in acidic soil with a pH rating from 4.5 to 5.5.
Knowing the acidity or the alkalinity of soil will help you grow healthy and productive plants. Gardening experts including Weekend Gardener recommend testing soil pH using special testing equipment like a pH tester. A good tester is easy to use, and it will help you test your soil anytime you want.
Do you have a lawn? Read 5 Lawn Care Tips for Greener Grass.
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