Why your soil test keeps saying low organic carbon

An analysis by the Centre for Science and Environment (CSE), published in October 2025, looked at about 1.3 crore soil samples tested under the Soil Health Card scheme in 2023-25. It found 48.5% of them low in organic carbon, and 64% low in nitrogen. If your own Soil Health Card says the same thing, you are not alone, and the number is worth understanding before you decide what to do about it.

What organic carbon actually does for your crop

Organic carbon is what lets soil hold water, release nutrients slowly instead of washing away, and support the microbial life that makes phosphorus and micronutrients available to roots in the first place. A field can test fine for nitrogen, phosphorus and potassium and still under-perform if the carbon that holds the whole system together has been depleted.

Why soil carbon runs low

Soil carbon is lost faster than it is put back when a field gets fertiliser but little organic matter in return. The habits usually blamed are heavy, unbalanced use of urea, burning crop residue instead of returning it to the field, and shorter crop rotations that give the soil less biological variety to work with. Which of these applies to your field is something only a look at your own history can tell you.

What a reading under 0.5% means for your next season

On the Soil Health Card, an organic carbon reading under 0.5% is rated low. At that level, a field typically holds water for less time after irrigation, responds less predictably to fertiliser (because there isn’t enough biological activity to make it available), and is more exposed to a bad monsoon in either direction: too little rain and it dries out fast, too much and nutrients wash straight through. It isn’t a one-season problem, but every season you wait, the gap gets a little more expensive to close.

Three ways to rebuild it

• Biofertilizer inoculation. Rhizobium, Azotobacter and PSB culture rebuild the microbial population that keeps nutrients cycling, without another synthetic pass.
• Biochar incorporation. A one-time, long-lasting improvement to water-holding and microbial habitat, worked in ahead of a season rather than reapplied every year.
• Reduced tillage and residue retention. The cheapest lever available: leaving more organic matter in the field instead of removing or burning it.

Which one is right for your field

The right starting point depends on what your own soil test says and what is grown there next. If you already have a Soil Health Card reading, look at the products for locked-up nutrients to match an input to the specific gap (phosphorus-locked, nitrogen-poor, or simply carbon-depleted) rather than defaulting to the same input every season.

Source

Centre for Science and Environment, analysis of Soil Health Card scheme data (National Mission for Sustainable Agriculture dashboard), 2023-25, released 27 October 2025: Indian soils severely deficient in essential nutrients.