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 procedure through which elements, such as potassium, phosphorous, sodium, magnesium, calcium, copper, manganese, sulphur, and zinc, are chemically removed from their 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 has many advantages, some of which are listed below:

• Soil analysis enables more informed fertilizer decisions, minimizing risks associated with soil erosion, infertility, and degraded lands, while enhancing long-term farm profitability.
• It identifies yield-limiting nutrients in the soil.
• It shows the amount of plant-available macronutrients in the soil and the location of these nutrients within the soil profile.
• It offers a basis for variable rate application (VRT) according to the soil and crop.
• It monitors the properties of soil health, such as EC, pH, and OC, which affect nutrient availability to crops, and thereby help enhance yield and profitability.
• It provides improved knowledge of soil types within the farm to select the ideal crop for your farm and enhances management options.
• Soil analysis supports decisions about fertilizer rate, placement, timing, and product.
• It helps enhance in-season responsiveness.

How to collect the 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

• You need to collect the soil sample during the fallow period. In case of standing crops, you should collect the samples between rows.
• You should 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.
• You need to 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.
• You should 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

• Fields should be divided into different homogenous units according to visual observations and the experience of farmers.
• 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 present, use a spade and make a V-shaped cut to a depth of 15 cm in 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 and remove the foreign materials, such as stones, roots, and gravel.
• Minimize the bulk to about half to one kg by quartering or compartmentalization.
• Dividing the mixed sample into four equal parts is known as quartering. You need to discard the opposite two quarters and remix the remaining two quarters and repeat the process until you get the desired sample.
• Spreading the soil over a clean, hard surface and 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?

After collecting soil samples, you can get your soil tested at a soil-testing laboratory, any garden centers, or a local cooperative extension office. Various types of tests are done to determine the overall characteristics of the soil, which are discussed below:

Soil Moisture Testing

This test determines moisture content in the soil sample. It involves high-temperature moisture evaporation from samples. You can calculate the moisture rates in the samples by comparing their mass before and after evaporation.

Soil Salinity Test

This test determines whether the farm is suitable for agriculture or not. 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

It is a chemical test used to determine 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 involves testing the level of pesticides present in the soil and scheduling 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, with lower values indicating acidity and higher values indicating 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

Soil testing is an important component of soil resource management. It helps farmers understand the characteristics of their farm soil, including soil properties and nutrient norms, so they can adjust their concentration accordingly. The Indian government has also 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 be aware of their soil condition so that they can use an adequate amount of fertilizers for better yield and keep the soil healthy. You can also explore Tractorkarvan to learn more about different types of soil in India.