ANALYTICAL SERVICES
Soil sample analysis
Soil Samples
Soil analysis gives the background knowledge on the chemical, physical and biological status of a soil that we need in order to properly manage our soils and crops.
Soil being the main medium for cultivation of crops, provides mechanical anchoring, support and being live is a home for numerous microbes which are beneficial for crop production and also is a Store House for many essential plant nutrients. The soil across the globe is not the same and shows varied characteristics which are unique to its formation and weathering process and is termed as Edaphic Factors! Soil has its own physical, chemical and biological properties derived from the parent material during weathering process and are very dynamic in nature which poses a challenge for cultivation of crops. Hence it becomes imperative to seek for soil sample analysis intermittently. Based on the soil analysis report, the fertilizers package of practices, manuring pattern, soil rectification measures and such other aspects could be handled well.
Why use soil analysis?
- It provides accurate and timely diagnosis of soil fertility related problems and enables to take decision on proper nutrient management strategy.
- It removes the guess-work and ad-hoc application of fertilisers; and provides scientific basis for choosing right product at right time with right rate of application.
- It helps to restore soil health in long term – since it advocates application of balanced nutrients and thus arrests soil mining.
Overall, it is a very efficient decision-making tool regarding nutrient management for all types of crops grown in various agro-climatic conditions.
What to analyse?
It takes considerable money and effort to collect and send a proper soil sample to the laboratory; besides the cost of analysis. Once the sample has arrived at the laboratory, there are a wide range of tests that can be conducted. Hence it makes sense to get as much information as possible from the sample analysis.
The type of sample to be collected depends on the objective and the type of crops.
(a) For study of soil genesis, soil sampling has to be done as per soil horizon in a profile.
(b) For studying soil fertility, sampling has to be done in the depth of ploughing layer.
(c) For shallow rooted crops like (paddy, tomato, sorghum etc.) sample has to be collected from the plough layer 15cm.
(d) for perennial crops (like Mango, areca nut, coffee, coconut, pomegranate and other fruit crops)- sample has to be collected from the depth of 45-52cm at the point away from the tree trunk.
Steps to be followed
1. Walk around the field in zig zag manner and mark the sub-sample points depending upon the size of the field. i.e., 15-20 sub-sample points for 5 acres (2.5Ha) of land.
2. Avoid places like compost pit, sloppy land, bunds and water leakage areas while taking soil samples.
3. Taking soil samples when field is completely wet should be avoided.
4. The surface should be scrapped to remove litter, stones etc., and collect samples into a bucket from each spot up to the required depth by making a ‘V’ shaped cut using a spade and a slice of soil is taken from both the sides. Around 250 – 350 gm from each sample points should be collected.
5. Such collected entire lot is placed on a plastic sheet / clean surface and mixed well by removing stones, roots and other plant residue.By following quartering method, the soil sample is reduced to 500 – 750 gm quantity and then the soil sample is then placed in a clean polyethylene bag by adapting quartering technique (as referred in the diagram)
Factors to be considered while soil sampling
1 | Size of area | 1 composite sample for every 2 ha (5A) |
2 | No. of sub samples | 15 to 20 sub samples per every 2 Ha |
3 | Depth of soil sampling | Shallow rooted crops: 0-15 cm (plough depth) Deep rooted and horticultural crops: Sample may be taken from different depths depending upon the root penetration (45 – 55 cm) |
4 | Frequency of sampling | Once in 2 years for dry land crops.Once after 2 crops in irrigated areas. |
5 | Time of sampling | Ideal time is one month before sowing/planting of seasonal crop. For perennial crops, immediately after the harvest of the crop, so that for the upcoming crop, the fertilizer schedule could be calculated. |
6 | Sampling in standing crop | Plantation/ fruit crops: On the canopy circumference |
Precautions to be taken while soil sampling
a) Avoid collecting soil sample near bunds, near roads, near FYM/ compost pits, below the trees, near buildings, near nalas/ streams/ ponds/ wet spots, irrigation canals and drainage lines and other unrepresentative spots.
b) Avoid collecting the soil sample immediately after application of fertilizers, manures and amendments. There should be minimum one month gap after application of fertilizer manures and amendments.
c) Avoid tools made of iron, copper and brass. Use only stainless steel, wooden, aluminium and plastic tools. If the soil sample has to be analysed for micronutrients.
d) Do dry the soil sample under shade before sending to laboratory, when the collected sample is wet. Avoid drying near fertilizer/chemicals/Pesticides go downs
e) Any sort of contamination should be avoided either through sampling tools or storage bags.
Soil test – based crop recommendation (STCR) provides accurate usage of fertilizers and manures, gives optimum yields & increases the Cost: benefit ratio & enhancing the Soil Health status year after year and crop after crop.
Category | Parameters | Purpose |
S-2 | Soil sample analysis pH, EC, Organic Carbon (%), C:N ratio, Sodium, Chloride, Avail. Nitrogen, Phosphorus, Potash, Exchangeable. Calcium, Magnesium. | For understanding the soil and its potential To know how good or how bad the soil is? |
S-3 | S2 + CEC + Total Calcium carbonates + Available Sulphur + Micronutrients – Trace elements (Iron, Manganese, Zinc, Copper, Molybdenum, Boron) | For understanding the yield potential |
S- 4 | S3 + Heavy metals analysis in Soil (Lead, Cadmium, Chromium). On request, any other Heavy metal of interest would be analysed. | For detection of heavy metal contamination in the soil. |