Healthy soil is a combination of minerals, rock, water, air, organic matter (plant and animal residue), microorganisms, including bacteria, fungi and protozoa and a variety of insects and worms. This intricate web carries out a process that continually replenishes the soil and maintains long-term soil fertility.
For sustained growth, plants require macro-nutrients and trace elements. Macro-nutrients include, nitrogen (N), phosphorous (P), potassium (K), calcium (Ca), magnesium (Mg) and sulfur (S). Trace elements include, iron (Fe), manganese (Mn), copper (Cu) and zinc (Zn). For optimum plant growth, soil must be capable of storing these nutrients and transferring them to the root surface for uptake by plants.
Various Procedures of Soil Sampling
Soil sampling is the most vital step for analysis. Soil sampling is done in order to find out the quantity of essential nutrients available to plants and other relevant physio-chemical properties which influence plant growth such as water retention, acidity, alkalinity etc.
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.