Previous Year Question
Consider the following agricultural practices :
Contour bunding
Relay cropping
Zero tillage
In the context of global climate change, which of the above helps/help in carbon sequestration/storage in the soil?
1 and 2 only
3 only
1, 2 and 3
None of them
Correct Answer: B
Detailed Solution
Carbon sequestration/storage means capturing atmospheric carbon through plants and retaining it for a relatively long period in the soil-organic-carbon pool.
1. Contour bunding — Incorrect
It involves constructing earth or stone embankments along lines of equal elevation.
Its primary functions are to slow runoff, control soil erosion and improve soil-moisture retention on slopes.
It may reduce the removal of carbon-rich topsoil, but contour bunding alone does not necessarily produce a net and assured transfer of atmospheric carbon into the soil.
2. Relay cropping — Incorrect
Relay cropping means sowing the succeeding crop before the standing crop has been harvested.
It can maintain vegetation cover for a longer period and may add organic matter through roots and crop residues.
However, the actual carbon outcome depends upon crop species, residue retention or removal, tillage and overall land management.
Relay cropping by itself, therefore, does not guarantee soil-carbon sequestration.
3. Zero tillage — Correct
Under zero tillage, soil is not extensively turned or ploughed before sowing.
Reduced soil disturbance limits the exposure of soil organic matter to air and can slow its oxidation and decomposition.
Consequently, the loss of carbon as carbon dioxide may be reduced.
Surface residue retention also supplies organic matter and improves aggregate stability, thereby favouring carbon retention, particularly in surface soil.
The actual result varies with climate, soil, crop rotation, residue management and measurement depth; nevertheless, among the given practices, zero tillage is the accepted answer.