Which practice is effective to increase soil carbon?

• A. Increased tillage
• B. Pesticide-only management
• C. Cover crops
• D. Frequent irrigation

Answer: (C)

This question focuses on how different farming practices affect soil carbon storage. Cover crops increase soil carbon by providing continual inputs of organic matter to the soil. While growing, these plants add biomass that becomes residue after termination and, crucially, their roots continuously deposit carbon-rich compounds into the soil. This sustained input helps build soil organic matter and stabilizes carbon in soil aggregates, especially when the soil is kept covered and biological activity is active.

In addition, cover crops protect the soil surface from erosion, reduce disturbance, and promote a healthier soil structure, all of which help retain carbon that would otherwise be lost with bare soil or during frequent tillage. Over time, this leads to higher soil carbon stocks compared with practices that leave soil bare, disrupt it with tillage, or fail to provide ongoing organic inputs.

Increased tillage tends to release stored carbon by exposing organic matter to air and speeding its decomposition, so it generally reduces soil carbon. Pesticide-only management doesn’t add organic matter or soil inputs that build carbon. Frequent irrigation can alter soil moisture and microbial activity in ways that don’t necessarily increase soil carbon and can even promote losses under some conditions.

So, cover crops are the most effective option for increasing soil carbon because they continually supply carbon inputs, protect the soil, and enhance conditions that stabilize and retain carbon in the soil.