Concept:Fallow land is left uncultivated so natural processes can restore lost plant nutrients in the soil.
Explanation:During the fallow period, weeds, grasses, and bushes grow freely on the land.
When this vegetation dies and falls to the ground, it decomposes over time.
Decomposition adds organic matter to the soil.
This organic matter breaks down further and releases essential nutrients like nitrogen, phosphorus, and potassium.
These nutrients become available for the next cropping season.
Thus, nutrient restoration during fallow is mainly through the accumulation of soil organic matter.
Answer:B. accumulation of soil organic matter