Rebuilding soil organic carbon on an Indian farm

Carbon is the property everything else rests on

Soil organic carbon is not one soil property among many. Structure, water-holding, cation exchange and biological activity all track it. When carbon falls, each of those degrades together, which is why a soil can pass a nutrient test and still perform badly.

This is also why adding more fertiliser to a low-carbon soil returns less each year. The nutrients are supplied; the soil's ability to hold and release them is not.

Why it fell

Intensive cropping with residue removed or burned takes carbon out every season and puts little back. Repeated tillage accelerates the loss by exposing organic matter to oxidation. Over decades, that is a large withdrawal from a slow-refilling account.

• Residue removed or burned rather than returned
• Continuous cropping with short or no fallow
• Repeated deep tillage
• Little or no organic amendment applied

What recovery actually looks like

Organic carbon rises slowly. A measurable change in a laboratory figure usually takes several seasons of consistent addition, not one application. What growers notice earlier are the working symptoms: the soil breaks up more easily, water goes in instead of running off, and beds stay moist longer.

Be sceptical of any supplier promising a dramatic carbon jump in one season. The chemistry does not move that fast, and a claim that big is a reason to check everything else they have told you.

A workable programme

Apply organic matter every season at a rate you can sustain, return crop residue where practical, reduce unnecessary tillage, and keep the soil covered when you can. Compost is the most controllable input in that list. It is the one you can order to a schedule and apply at a known rate.