Testing Moisture In Plants: How To Gauge Soil Moisture In Plants

Testing Moisture In Plants: How To Gauge Soil Moisture In Plants

By: Mary H. Dyer, Credentialed Garden Writer

Adequate moisture is critical for growing plants successfully. For most plants, too much water is more dangerous than not enough. The key is to learn how to gauge soil moisture effectively and to water plants only when they need it, not on a set schedule.

Checking Plant Moisture

When it comes to testing moisture in plants, the feel of the soil is the best guide. As a general rule, a potted plant in a container measuring 6 inches (15 cm.) in diameter needs water when the top 2 inches (5 cm.) of soil feels dry to the touch. A larger container measuring 8 to 10 inches (20-25 cm.) in diameter is ready for water when the top ½ to 1 inch (1.25-2.5 cm.) of soil feels dry.

Insert a trowel into the soil, then tilt the trowel to check the moisture of garden plants. You can also insert a wooden dowel into the soil to determine the depth of soil moisture. If the dowel comes out clean, the soil is dry. Damp soil will cling to the dowel.

In most cases, the soil should be damp to the root zone – 6 to 12 inches (15-30 cm.). However, sandy soil drains quickly and should be watered when the soil is dry to a depth of 2 to 4 inches (5-10 cm.).

Remember that the need for water also varies widely depending on the plant. For example, most succulents require dry soil and infrequent watering while some plants, such as columbine, prefer consistently moist soil. However, nearly all plants require air circulation around the roots and are prone to rot in poorly drained, waterlogged soil.

Soil Moisture Tools

Soil moisture monitoring can also be achieved with specific tools. A variety of simple, inexpensive soil moisture meters are available in garden centers and nurseries, and many are suitable for both indoor and outdoor growing. The meters, which tell you if the soil is wet, moist, or dry at the root level, are especially effective for large potted plants.

Other soil moisture monitoring tools, often used for agricultural applications, include tensiometers and electrical resistance blocks, which indicate the moisture tension of the soil. Although both are accurate and easy to operate, they are more expensive than simple probes.

Time Domain Reflectometry (TDR) is a newer, more expensive method that measures soil moisture quickly and accurately. However, the sensor often requires recalibration and the data tends to be relatively difficult to interpret.

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7 Best Soil pH Tester Reviews: Grow Strong and Healthy Plants in Perfect Soil Conditions

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A soil pH tester is a valuable tool for any gardener. Whether you grow flowers, fruit, vegetables, or herbs, a soil pH tester accurately measures the condition of the soil so that your plants have the perfect environment where they can flourish.

Create Perfect Soil Conditions with an Accurate Soil pH Tester Meter

Cultivating perfectly pH balanced soil is incredibly important for your plants’ health. A soil pH tester shows you the accurate pH level of the soil in your garden beds or plant pots. It will tell you if the soil is too alkaline or acidic. When the soil has the right pH balance, your plants will thrive.

One of the most versatile gardening gadgets, a soil pH tester, or soil pH meter, can be used for home gardens, urban gardens, fruit tree orchards, farming, or other types of commercially-grown plants. So whatever type of garden you have, the amazing soil tester should always be the first step in your plant-caring regime.

Before you choose the right plant food, which provides beneficial nutrients, as well as the sun and rain, your soil pH tester accurately measures the condition of the soil. After you have determined the acidity or alkalinity level of the soil, you can confidently plant your flowers, fruits, vegetables, or herbs which will produce beautiful foliage and a bountiful harvest.

Best 3-Way Meter: Hydro Crunch 3-in-1 Soil Moisture Meter

If you’re looking one device to give you a more in-depth picture of soil conditions, consider a 3-way moisture meter that is also capable of measuring light and pH levels. This 3-in-1 moisture meter from HealthyWiser uses a metal probe to determine moisture levels on a scale from 1 to 10 and also registers pH on a scale from 3.5 to 8. A photovoltaic cell on the front of the device measures how much light is received in any given location, indoors or outdoors.

Gardeners have appreciated that the pH value helps to optimize soil conditions for citrus plants along with other fruit plants. This 3-way moisture meter can also help you to determine the best spot in your garden for a plant-based on its needs—for example, more acidic soil and a shady spot for hydrangeas. Many users find this tool to be an indispensable ‘gardener’s helper’ and use it to maintain optimal conditions for their plants.

Luster Leaf Rapitest Soil Tester

Luster Leaf Rapitest Soil Tester is a traditional chemical test process and we like it, back to basics. This economical soil test kit for testing soil pH, Nitrogen (N), Phosphorus (P) and Potash (K) is simple and reliable.

The kit contains 4 pH test capsules and 2 each of N-P-K. I have always enjoyed this type of test kit and the children usually like to get involved as its a little bit reminiscent of the chemistry experiment’s they do at school. So if you don’t need ultra-accurate results, and if you don’t need to perform lots of repetitive tests, then this type of kit is always very cost effective and fun.

How to use: Take a sample of soil preferably from around 3″ deep. Mix it with water and shake. Transfer some of the solution to the soil comparator as a benchmark. Mix in the capsule and shake again. Match the solutions color to the color chart to get your reading.

Customer Reviews: Customers who used this product gave it an overall score of 4/5, with a general appreciation of the accuracy. Some user found the test difficult to read due to the solution color looking muddy from the soil.


  • Cost effective is you only need one or two tests
  • Fun to use and get the children involved


Conclusions and recommendations

Although the need for good and appropriate measurements of water status is well recognized for studies of water movement in the soil–plant system and in crop physiology, such measurements are often not made in more molecular studies. An associated problem is that the drought treatments imposed in many molecular studies are often rather unrealistic so that the results may have little relevance to the common objective justification of the work to ‘improve agricultural production’. It would seem that enhanced inputs from environmental plant physiologists could benefit experimental design and enhance the value of the molecular studies for agricultural purposes. In general, although any measure of water status is better than none, a choice of measures including both the environmental stress and the plant water status will substantially enhance the information obtained. What is required for future experiments is a greater use of repeatable protocols that allow researchers to identify specific genes explicitly related to key processes involved in drought tolerance for incorporation into new varieties.

Part of the work described here was supported by the UK Department for the Environment, Agriculture and Rural Affairs under project HH3609TX.