Wish to make your plants thrive? Ever tried testing the pH of your soil? If you’re worried about the stunted growth of your plants, maintaining healthy soil is the first step towards rectifying it. And you can proceed with maintenance only when you know what’s exactly wrong with your soil. That is when chemical soil testing comes into action.
Be it optimizing crop production, protecting the environment from contamination by runoff, leaching of excess fertilizers, or improving the nutritional balance of the growing media, soil testing is essential for a plethora of reasons.
This all-encompassing blog will guide you through soil testing and can be especially beneficial for those who are just starting out.
What is Soil Testing & Analysis?
Soil analysis typically refers to a set of varied chemical processes that determine the number of accessible plant nutrients within the soil.
The nutrients include nitrogen (N), phosphorus (P), and potassium (K), which are the most important nutrients for crops. Secondary nutrients to examine are calcium (Ca), sulfur (S), and magnesium (Mg). An extended test also includes minor elements like iron (Fe), manganese (Mg), boron (B), molybdenum (Mo), and others
pH, Humus content, accessible lime, organic matter, total sulfur, total CaCo3, and a plethora of physical characteristics.
What are the Objectives of Soil Testing?
Soil testing is done for several reasons:
- Increase knowledge about the soil condition and how to improve it
- Evaluating the fertility and nutrient status of the soil helps to determine an index of nutrient availability or supply in each soil
- To minimise fertiliser expenditures
- Determining the acidity, salinity, and alkalinity problems
- Providing a recommendation on the amount of fertilizer and manure based on crop and soil test value
- Ensuring environmental safety by avoiding excess use of fertilizers
- Evaluating the suitability of the soil for the plants
- Restoring the soil fertility
- Predicting the probability of obtaining a profitable response to fertilizers
- To promote plant health and Nutrient management.
When is the Right Time for Soil Analysis?
This is one of the most significant aspects to consider when analyzing soil quality. Make sure that you take the sample soil after the harvest. This allows farmers sample time to plan fertilization management. And, when it comes to perennial crops, the best time for soil analysis is during the dormancy stage.
If you wish to achieve higher yields, you must focus on maintaining quality and balanced soil. So, it is recommended you collect soil samples frequently (once every 2-3 years). This will help you detect any changes that could affect your crop yield.
When growing annual crops, it is suggested that you practice soil analysis after every third crop in rotation.
How to Take a Soil Sample for Analysis?
If you think that taking a soil sample is all about taking a patch of dirt to a soil testing lab, you might be much farther away from the facts. For getting the most accurate soil test results, you must make sure that the sample you collect is from an accurate dissection of your field. Taking samples by the probe is the best way to do that.
You can use a shovel as well; in case the probe is not available. However, for doing that, you must follow a specific procedure:
- Dig a pit
- Dig out the soil vertically along the pit wall
- Pull out the shovel properly so that the soil does not slip off it.
- Remove approx. 5 cm of soil to the left and right of the shovel
- Collect the soil as your sample that remains longitudinally along the middle of the shovel
Once you’ve collected the sample, it is placed in a plastic bag with the following information:
- Name of owner and an address
- Depth of sampling
- The name of the crop sown for which soil samples are taken
- Date of sampling
- Sampler Name
- Sample Qty
Now, that we know what soil analysis is and how the sampling is done, let’s talk about the most common test, pH, Salt Concentration (Electrical Conductivity)
What is pH?
pH as a measurement helps you determine how acidic or basic your soil sample is. When you are testing pH in any soil, you’re measuring the number of hydrogen atoms carrying a positive charge.
The higher the concentration of hydrogen ions is, the more acidic your soil sample is, and vice versa. If the pH is between 0 and less than 7 on the pH scale, the soil will be considered acidic. And, if it comes between more than 7 and 14 on the scale, the soil will be considered basic and 7 pH soil will be considered as neutral.
pH Rating of Soil
Less than 4.5 Extremely Acidic
4.6 to 5.2 Strongly Acidic
5.3 to 6.0 Moderately Acidic
6.1 to 6.5 Slightly Acidic
6.6 to 7.0 Neutral
7.1 to 7.5 Slightly Alkaline
7.6 to 8.3 Moderately Alkaline
8.4 to 9 Strongly Alkaline
More than 9 Extremely Alkaline
Factors Affecting Soil pH
Here are a few things that can affect soil pH to the greatest extent. Let’s discuss them in brief detail.
Climate and Weather
This is one of the most prominent factors that influence soil pH. Be it temperature, precipitation, sunlight, and seasonal weather changes, every climatic factor affects the pH of the soil. For instance, high precipitation tends to wash essential nutrients out of the soil. As most of the nutrients are basic, they make the soil acidic when they leave.
When decaying material in the soil gets washed off by water, it also causes the pH to drop. This is because decaying material releases carbon dioxide. And, when this CO2 is mixed with water, acids are formed.
Plants
Local ecology and native plants tend to determine the pH of your soil to a great extent. While the soil under the grasses is usually less acidic, the ones under trees tend to be more acidic.
Soil Type
The parent materials from which the soil in your region is made affect its nature to a great extent. Areas with a lot of limestones are more basic and areas rich in shale are more acidic.
Nutrient Availability
If the soil pH is too low or too high, plants cannot absorb nutrients. When pH is not up to the mark, certain nutrients like calcium and phosphorus will bind up with other things in the soil. Plants will not be able to take in what they need to thrive when the nutrients become bound up.
If the pH is too high, nutrients like iron become bound. If the plants are not able to take in adequate iron, they’ll lose their chlorophyll and start to turn yellow. Molybdenum poisoning occurs generally in soils with alkaline pH.
What is Electrical Conductivity of Soil?
Conductivity is a measurement of current carrying capacity, which gives idea about the soluble salts (Ex – Ca, Mg, Na, K, N) present in soil samples.
Air-dried soil is extracted with water at 25°C at an extraction ratio of I:2 (m/v), to dissolve the electrolytes. The specific electrical conductivity of the suspension extract is measured with the help of electrical conductivity meter. Normally reported in dS/m or milimhos/cm and the value gives information on the total amount of the soluble salts present in soil, i.e., on the degree of salinity.
Ratings: EC in dS.m–1
0 to 1 Good soil
1 to2 poor seed emergence
2 to 4 Harmful to some crops, e.g., Pulses.
Above 4 Harmful to most of crops.
The Bottom Line
Soil testing and analysis might seem like an unnecessary hassle but attempting to amend existing soils or replacing them altogether can be even more challenging. We recommend you get the soil tested for avoiding issues like stunted plant growth and soil contamination.
Trust our qualified and experienced experts for thorough soil quality testing and analysis. Our fast turnaround time and precise test results make us stand out. Count on our tailor-made solutions for getting all your testing needs fulfilled.
If you have any queries or are thinking of getting your soil tested before taking on a new project, feel free to get in touch with us.
Citations:
https://blog.hannainst.com/soil-ph-testing
https://krishijagran.com/agripedia/soil-testing-purpose-of-doing-soil-analysis-how-to-do-it/
https://www.harvestogroup.com/post/soil-testing-importance-and-benefits
https://www.agrivi.com/blog/why-successful-farmers-practice-soil-analysis/
Singh, Dhyan, Chhankar, P.K. and Pande R.N., 1999, Electrical Conductivity in Soil, Water analysis Method Manual, IARI, ICAR, New Delhi, 1 : 4.2 (b) 14-16.