A Comprehensive Guide on Soil Testing in India: Benefits & Process

Table of Contents

• What is Soil Testing?
• What are the Benefits of Soil Testing in India?
• How to Collect Soil Sample?
  • Materials Needed for Soil Sampling
  • Points to be Considered for Soil Sampling
  • Method to be Followed for Soil Sampling
• How is Soil Tested?
  • Soil Moisture Testing
  • Soil Salinity Test
  • Soil Nutrient Testing
  • Soil Testing for Pesticides and Contaminants
  • Soil Acidity Test (pH)
  • Physical Soil Testing for Texture and Structure
• How to Read a Soil Test Report?
• Conclusion

What is Soil Testing?

Soil testing is the process of determining the physical, chemical and biological properties of soil. It is a procedure through which elements, such as potassium, phosphorous, sodium, magnesium, calcium, copper, manganese, sulphur, and zinc, are chemically removed from the soil and measured for their available content within the soil sample. It is an important diagnostic tool for knowing the nutrients for crops.

What are the Benefits of Soil Testing in India?

Soil testing provides many benefits to farmers in India, some of which are listed below:

• Soil testing reduces farmers' input costs and enables them to make informed decisions about buying the right fertilizers, thereby minimizing the risks associated with soil erosion, infertility, and degraded land while enhancing long-term farm profitability.
• Soil testing helps determine the right amount of nutrients for the soil, which improves yields.
• It provides improved knowledge of soil types on the farm to select the ideal crop and enhances management options.
• Healthy soil is resistant to drought and floods, which ensures stability in uncertain weather.
• Soil testing also helps prevent overfertilization.
• It helps enhance in-season responsiveness.
• Applying the necessary nutrients also reduces the risk of environmental contamination, promoting sustainable farming practices.

How to Collect Soil Sample?

The collection of soil samples involves different steps. Let’s discuss them in detail:

Materials Needed for Soil Sampling

• Sampling bags
• Khurpi
• Spade or auger (screw or tube, or post hole type)
• Core sampler
• Plastic tray or bucket

Points to be Considered for Soil Sampling

• Collect the soil sample during the fallow period. In case of standing crops, you should collect the samples between rows.
• Collect samples in a zigzag pattern at several locations, as it ensures homogeneity.
• Farms with similar appearances, production, and post-management practices can be grouped into a single sampling unit.
• Collect separate samples from farms that vary in slope, color, drainage, past management practices, such as fertilization, gypsum application, liming, cropping system, etc.
• In case of shallow-rooted crops, you need to collect samples up to 15 cm deep. In case of deep-rooted crops, the samples should be collected up to 30 cm deep. In case of tree crops, you need to collect profile samples.
• Avoid sampling in dead furrows, areas near the main bund, wet spots, manure heaps, trees, and irrigation channels.

Method to be Followed for Soil Sampling

• Divide the field into homogeneous units based on visual observations and farmers' experience.
• Eliminate the surface litter at the sampling spot.
• Operate the auger to a plough depth of 15 cm and draw the soil sample.
• Take at least 10–15 samples from each sampling unit and place them in a tray or bucket.
• If no auger is available, use a spade to make a V-shaped cut to a depth of 15 cm at the sampling spot.
• Remove thick slices of soil from the top to the bottom of the exposed face of the ‘V’ cut made through the spade and put it in a clean container.
• Mix the samples thoroughly, then remove any foreign materials, such as stones, roots, and gravel.
• Minimize the bulk to about half to one kg by quartering or compartmentalization.
• Dividing a mixed sample into four equal parts is called quartering. You need to discard the two opposite quarters, remix the remaining two, and repeat the process until you get the desired sample.
• Spreading the soil over a clean, hard surface, dividing it into smaller compartments and drawing lines along and across the length and breadth is known as compartmentalization. You need to collect a small amount of soil from each component and repeat the process until you obtain the desired sample.
• Put the sample in a polythene bag or a clean cloth.
• Label the bag with details, such as the farmer’s name, farm location, survey number, previous crop grown, crop to be cultivated in the next season, present crop, collection date, sampler name, etc.

How is Soil Tested?

Soil testing is performed in soil laboratories, garden centers, or local cooperative extension offices after soil samples are collected. Different types of tests are done to determine the overall characteristics of the soil, which are discussed below:

Soil Moisture Testing

Soil moisture testing determines the moisture content of a soil sample. It involves high-temperature evaporation of moisture from samples. You can calculate the moisture content of the samples by comparing their masses before and after evaporation.

Soil Salinity Test

This test determines whether the farm is suitable for agriculture. Soil salinity can be obtained through different methods, such as:

• The total soluble salts (TSS) evaporate from the groundwater extract.
• Measurement of saturated paste extract or a distilled water-earth dilution’s electric conductivity (EC).
• Testing electric conductivity in the field or in a laboratory.

Soil Nutrient Testing

This is a chemical test which determines the levels of primary, secondary, and minor elements in the soil. The primary elements include Potassium (K), Phosphorous (P), and Nitrogen (N). The secondary elements include Magnesium (Mg), Sulphur (S), and Calcium (Ca). The minor elements are Manganese (Mn), Iron (Fe), Molybdenum (Mo), and Boron (B).

Soil Testing for Pesticides and Contaminants

This test is needed to assess soil pesticide levels and to schedule subsequent crop treatments based on earlier field operations and productivity.

Soil Acidity Test (pH)

In this test, hydrogen ions are calculated in the soil by testing its pH, which goes from 0 to 14. The neutral pH value is 7; lower values indicate acidity, and higher values indicate alkalinity. Farms that are acidic or alkaline are treated differently.

Physical Soil Testing for Texture and Structure

This test examines the soil type and its physical features, such as texture, structure, and wetness, along with chemical content. The key components in this test are sand, clay, and slit, and their quantity determines the soil texture and its ability to hold nutrients and moisture.

How to Read a Soil Test Report?

A soil test report usually features the results on the specified parameters, and the volumes of the chemical elements present in the samples. Thus, it is crucial to know nutrient norms and adjust their concentrations correspondingly. The table below shows the rating charts for soil test data:

Soil Nutrient Content:

Soil pH:

Total Soluble salts (Conductivity in milli mhos/cm2):

Conclusion

For a sustainable future and agricultural growth, farmers need to address the challenges hindering soil testing. The best way for farmers to test their soil is to locate the nearest authorized soil-testing lab. Also, the Indian government has launched several schemes that help farmers get their soil tested and improve their farm’s yield. The Soil Health Card Scheme was launched by the government to help farmers understand their soil condition, so they can use an appropriate amount of fertilizers to improve yields and keep the soil healthy.