Why does humus tend to increase with the clay content of soil? A. As the clay content increases, the amount of plant lignin in the soil increases. B. As the clay content increases, there is more surface area in the soil for organic matter to adsorb to, which increases the rate of decomposition. C. As the clay content increases, the permeability decreases, which increases the rate of decomposition. D. As the clay content increases, there is more surface area in the soil for organic matter to adsorb to, which decreases the rate of decomposition.

Answer: B. As the clay content increases, there is more surface area in the soil for organic matter to adsorb to, which increases the rate of decomposition.

Explanation:

Clay is a finely grained material obtained from the weathering of the natural rock. It is mixed with the valuable materials such as metal oxides, organic matter, quartz which are mostly composed of phyllosilicate minerals that contains a variable amount of water trapped minerals. The clay in any type of soil increases the surface area for the absorption of water and organic matter. The increase in the organic matter in the soil will increase the abundance of soil microbes which increases the rate of decomposition of the dead and decaying matter like shed leaves, dried grasses and animal dung. This helps in formation of humus in the soil and keeps the soil fertile.