How to Collect Samples and Interpret Results for Soil Testing

The quality of the farmland determines agricultural production, and a soil test may quickly identify issues with crop growth conditions. An examination of field suitability aids in selecting the right crops or determining how to use land for farming.

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In the end, routine soil testing is crucial for producers as well as for all other agribusiness participants, such as agri-coops, crop insurers, banks, input suppliers, or commodity dealers, since it may offer insightful information from the field. However, approved laboratories only provide information on the field’s existing characteristics. Therefore, it’s preferable to integrate lab reports with historical data from satellite imagery analytics when reviewing soil test findings for judgments on field amelioration.

Soil Testing: What Is It?

It is an investigation of farmland for a variety of factors, including salinity, pH, toxicity, chemical content, and earth-dwelling biota. In addition, these tests reveal details on various physical and chemical characteristics, humic or organic content, electric conductivity, cation exchange capacity, and chemical contamination.

Types Of Tests On Soil

The method of analysis chosen will rely on the field ground’s investigated components or features that might have a positive or negative influence on crop development. The most popular forms of analysis and measurement are:

mineral composition,

pH scale,

soil wetness,


insecticides and the pollution of chemicals,

composition, feel, etc.

Nitrogen Testing in Soils

In precision agriculture systems, precise fertilization to fulfill plant demands is made possible by valuable information on nutrient content. For this reason, the most used test for soil nutrients is the chemical test.

The three most crucial elements for crops—nitrogen (N), phosphorus (P), and potassium (K)—are the main subjects of soil test results. Sulfur (S), magnesium (Mg), and calcium (Ca) are secondary nutrients to look at. Minor elements such as iron (Fe), manganese (Mg), boron (B), molybdenum (Mo), and others are also included in an extended test.

A sample is added to an extractant solution and stirred (usually by shaking) to determine the nutrient content of the soil. The liquid content is then filtered and subjected to analysis to determine the amounts and existence of chemical constituents (converting it to dry matter). The soil-test index is the resultant number.

H (pH) Soil Acidity Test

For plants to be productive in the field, the pH level must be right; either too high or too low will have a negative impact on crop development. Calculating the hydrogen ions in soil requires testing its pH. The pH scale has values between 0 and 14. Seven is the neutral number; lower values indicate acidity, whereas alkalinities above seven are greater than that. Fields that are acidic or alkaline are handled appropriately. Lime, for instance, may be used to boost pH, and the right pH test can assist estimate how much is needed.

Soil Salinity Measurement

Plants under salty conditions experience osmotic stressors as a result of inadequate water uptake. Testing the salinity of the soil is one way to determine if a piece of land is suitable for farming. Analysis of field salinity can be done using:

the groundwater extract’s total soluble salts (TSS) evaporating;

determining a saturated paste extract’s or distilled water-earth dilution’s electric conductivity (EC).

Checking Soil for Contaminations and Pesticides

Pesticides aid in the management of any harmful organisms that ruin crops. Chemicals are useful in controlling agricultural diseases, controlling weeds, and eliminating pests. These toxins can contaminate the environment and harm creatures that are not their intended targets. Extremely harmful toxins damage people and animals, seep into groundwater, linger on the soil for years, and build up in food.

Testing the texture and structure of the soil physically

Agricultural soil testing examines the kind of soil as well as its physical characteristics, such as moisture, structure, and texture, in addition to its chemical composition.

The three primary constituents, namely silt, sand, and clay, determine the texture of the ground as well as its capacity to hold onto moisture and nutrients. A soil texture test aids in the precise planning of fertigation and irrigation since, for instance, sandy fields dry out more quickly than clay ones.

The size of the components and pore spaces in soil determines how air and water move through the soil. Smaller pore spaces and finer textures characterize clay fields. As a result, they need frequent aeration and are prone to compaction.

Testing for Soil Moisture

Plants require water to flourish, and without ground moisture, vegetation cannot grow as it should. Although the surface of the field can be seen to be dry, precise water rates are determined in a lab or using soil moisture sensors. A test for soil moisture content indicates whether plants are dehydrated or have access to water. The standard soil moisture test involves evaporating moisture from samples at high temperatures. The samples’ masses both before and after evaporation are used to calculate the moisture rates in the samples.

To achieve excellent yields, it’s critical to keep an eye on the field’s moisture levels both before and throughout the planting season. Remotely monitoring the root-zone and surface moisture levels is possible with EOSDA Crop Monitoring. Additionally, historical data indicates the moisture content at every stage of plant growth. Farmers are able to forecast the moisture deficit and make informed judgments by using this data. Furthermore, the EOSDA Crop Monitoring NDMI index aids in identifying important zones, and additional soil moisture measurement in these locations will reveal whether or not they are indeed dehydrated.

An association between soil moisture and NDVI is seen in the chart below. On loamy soil, 65% humidity is the ideal amount for growing sunflowers. You may reduce it by 40% and still maintain the highest payout. The NDVI shows that the humidity falls below the wilting point in June, which is 25%. In this instance, the model indicated that rather than the maximum probable yield of 3961 kg/ha of crop, the harvesting produced 2374 kg/ha of crop.