Soil and Water Testing

A well equipped lab is available to diagnose the soil fertility status of the district and to emphasise the importance of soil analysis to farmers. So for nearly 15000 soil and water samples are analyzed

Importance of Soil
Soil is the basis for food, feed, fuel and fibre production and for services to ecosystems and human well-being. It is the reservoir for at least a quarter of global biodiversity, and therefore requires the same attention as above-ground biodiversity. Soils play a key role in the supply of clean water and resilience to floods and droughts. The largest store of terrestrial carbon is in the soil so that its preservation may contribute to climate change adaptation and mitigation. The maintenance or enhancement of global soil resources is essential if humanity’s need for food, water, and energy security is to be met.
Soil needs to be managed in a sustainable way. This will be achieved when the supporting, provisioning, regulating, and cultural services provided by soil are maintained or enhanced without significantly impairing either the soil functions that enable those services or biodiversity.
Human pressures on soil resources are reaching critical limits, inherently reducing or eliminating soil functions critical to human well-being. Soil degradation is a pervasive process that in its various forms affects all regions. One third of all global soils are already degraded, affecting mainly smallholders and family farmers, who are responsible for 80% of the food production in value terms
How to Keep Soil Healthy
Healthy soil is important. It gives your plants food and water and helps them grow and give higher yield with less effort. Good soil is dark-colored and crumbly when you feel it with your fingers. To keep your soil healthy, remember to:

  • Use well-drained soil
  • Avoid soil erosion
  • Stay off wet soil
  • Add compost to improve your soil
  • Have your soil tested
  • Apply recommended fertilizer and lime rate

Well drained soil
A well-drained soil dries fast and permits timely field operations. In well-drained soil oxygen is able to reach the root zone to promote optimal root health. Optimal root growth happens best in soils without drainage problem.
Stay off wet soil
Driving on wet soil will pack soil down and push out the air and water will not pass through the soil. There will not be enough space for the roots to grow. Soil that is too packed will not give good crop yield. Wait until the ground is dry before you till it or start planting.
Add compost to your soil
Compost is a mixture of plant wastes or residual and roots and leaves. Adding compost to your soil will improve soil nitrogen and plants give more yields. If your soil is heavy clay, adding compost will help the soil drain water. If your soil is sandy, adding compost will help the soil hold more water. Adding compost brings earthworms and other living things that help plants and roots grow strong and healthy.
Have your soil tested
Soil testing is the base for management decisions about fertilizer requirements. It involves the estimation and evaluation of the available nutrient status and acidic reaction of a sample of soil. After testing, a fertility map is prepared where the available nitrogen, phosphorous and potassium is marked as low, medium or high. Areas of sufficient and insufficient nutrients are marked out and nutritional requirements are determined. Fertilizers such as NPK, lime or gypsum are recommended to improve soil fertility. Fertilizer addition, which is based on soil testing, usually leads to an increase in yields and profits by providing the correct amounts of needed nutrients. It also leads to uniform application of nutrients in a field. As nutrient availability becomes less variable, the crop growth is more uniform. Regular soil testing also contributes to environmental sustainability as the use of excess fertilizers can be avoided.
How to collect soil sample

  • Collect the soil sample during fallow period.
  • In the standing crop, collect samples between rows.
  • Sampling at several locations in a zig-zag pattern ensures homogeneity.
  • Fields, which are similar in appearance, production and past-management practices, can be grouped into a single sampling unit.
  • Collect separate samples from fields that differ in colour, slope, drainage, past management practices like liming, gypsum application, fertilization, cropping system etc.
  • Avoid sampling in dead furrows, wet spots, areas near main bund, trees, manure heaps and irrigation channels.
  • For shallow rooted crops, collect samples up to 15 cm depth. For deep rooted crops, collect samples up to 30 cm depth. For tree crops, collect profile samples.
  • Always collect the soil sample in presence of the farm owner who knows the farm better


  • Divide the field into different homogenous units based on the visual observation and farmer’s experience.
  • Remove the surface litter at the sampling spot.
  • Drive the auger to a plough depth of 15 cm and draw the soil sample.
  • Collect at least 10 to 15 samples from each sampling unit and place in a bucket or tray.
  • If auger is not available, make a ‘V’ shaped cut to a depth of 15 cm in the sampling spot using spade.
  • Remove thick slices of soil from top to bottom of exposed face of the ‘V’ shaped cut and place in a clean container.
  • Mix the samples thoroughly and remove foreign materials like roots, stones, pebbles and gravels.
  • Reduce the bulk to about half to one kilogram by quartering or compartmentalization.
  • Quartering is done by dividing the thoroughly mixed sample into four equal parts. The two opposite quarters are discarded and the remaining two quarters are remixed and the process repeated until the desired sample size is obtained.
  • Compartmentalization is done by uniformly spreading the soil over a clean hard surface and dividing into smaller compartments by drawing lines along and across the length and breadth. From each compartment a pinch of soil is collected. This process is repeated till the desired quantity of sample is obtained.
  • Collect the sample in a clean cloth or polythene bag.
  • Label the bag with information like name of the farmer, location of the farm, survey number, previous crop grown, present crop, crop to be grown in the next season, date of collection, name of the sampler etc.

After your soil is tested, you will get the results in the form of soil health card and will be sent through mail as well. These results will tell you if your soil needs more nutrients. Then you can decide to add more compost or to use fertilizer.
Be careful with fertilizer
Fertilizers can hurt plants if they are used wrong. The right amount and the right kind of fertilizer make your soil good and healthy without wasting fertilizer or money. Use only what you need. If you do not understand the directions, call your Agricultural Officer.
 Soil fertility refers to the ability of a soil to sustain plant growth, i.e. to provide plant habitat and result in lasting constant yields of high quality.
The natural fertility of soil depends on several factors.  The composition of the soil, the slope of the land, which affects drainage, the climate and local weather and the ease of cultivation all affect the natural fertility of the soil.
Traditionally, shifting cultivation where the land is cleared, crops grown until the yields become too poor and then another plot of land is cleared has been a method of restoring and maintaining fertility.  Bushes help improve soil structure because their roots open up the soil so that water can infiltrate more easily.  Continual plant cover helps prevent water and wind erosion
A fertile soil has the following properties:

There is very little or indeed nothing that a farmer can do about these factors.  However, good soil management can improve the soil conditions and build up soil fertility.  The Government of India and Government of Tamil Nadu are taking lot of steps through farm scientists and extension officials to maintain soil healthy for healthy life by distribution of soil health card to individual farmers so as to improve the agricultural productivity and income of the Indian farmers.  Maintaining Healthy soil will also lead to ever green revolution and sustainable agriculture development in India.