The nutrients in topsoil that support plant growth come from a. pesticides used by farmers b. minerals trapped inside of rocks c. materials located below the earth’s outer crust d. plant and animal matter that is decaying

d. plant and animal matter that is decaying

Explanation:

The topsoil, also referred to as O Horizon, is the top layer of the soil. It is the soil that is the richest with nutrients, which of course is very welcomed by the plants, as they need those nutrients for growth.

The nutrients in this layer of the soil come from the decaying animal and plant matter. When an animal dies, or a plant dies or part of it, they start to decompose and release nutrients in the soil. This doesn't just happen on its own, but instead it is done by microbes.

The rate of decomposition depends a lot on the climate conditions though, so it can easily be noticed that the regions that have warmer climate with higher humidity have higher rates of decomposition, thus having bigger layers of topsoil rich in nutrients. The colder areas have much slower rates of decomposition because there are much less microbes present, while the hot and dry areas have rates that are too rapid for the bio-matter to pile up and make a layer.

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