Question

Usable forms of nitrogen can intentionally be increased in the soil by

planting more trees.
planting more trees.

allowing organic matter to decompose.
allowing organic matter to decompose.

lightning.
lightning.

planting fewer beans.

Answer 1

Usable forms of nitrogen in the soil can be intentionally increased by:

1. **Planting more trees** - Trees can contribute to nitrogen levels through processes like nitrogen fixation and leaf litter decomposition.

2. **Allowing organic matter to decompose** - Decomposition of organic matter releases nitrogen as it breaks down, making it available for plant uptake.

3. **Lightning** - While not intentional, lightning converts atmospheric nitrogen into usable forms (nitrates) that are deposited in the soil through rain.

4. **Planting fewer beans** - This is not a method to increase usable nitrogen. In fact, beans and other legumes can fix nitrogen in the soil, so planting fewer beans could lead to a decrease in nitrogen levels.

To summarize, the two methods that intentionally increase usable nitrogen are **planting more trees** and **allowing organic matter to decompose**.