Consider the following agricultural practices: In the context of global climate change, which of the above helps/help in carbon sequestration/storage in the soil?

Answer: (c) 1, 2 and 3 only

All three help build or keep soil carbon.

Statement by statement

1. ✓ YES Bunds stop topsoil (and its carbon) from washing away.

2. ✓ YES Keeping crops on the field year-round adds more roots and residues to the soil.

3. ✓ YES Not ploughing leaves soil carbon undisturbed and residue on the surface.

The idea

Soil carbon is the dead roots, leaves and other organic matter in soil. Soil loses it in two ways: ploughing exposes it to air and microbes burn it up, and erosion washes it away. Soil gains it when more roots and residue are added. Each of the three practices does one of these jobs.

Contour bunding → stops topsoil from washing away → carbon stays → Relay cropping → field is never bare → more roots and residue → Zero tillage → soil is not turned → carbon is not exposed to air

The trap

Contour bunding sounds like erosion control only — which is exactly how it keeps carbon.

Also know

Relay cropping means sowing the next crop before the standing crop is harvested. Zero tillage is used for sowing wheat into rice stubble with the Happy Seeder, which also avoids stubble burning. The world’s soils hold more carbon than the atmosphere and all vegetation together. The “4 per 1000” initiative launched at COP21 aims to raise soil carbon by 0.4% a year.