Nitrogen is an essential component of all living things. However, atmospheric nitrogen is unavailable for organisms to use. Through various processes and chemical changes, nitrogen moves through the biosphere, atmosphere, and geosphere in different forms, making it available for all organisms. Atmospheric nitrogen is deposited in the soil and surface waters primarily through precipitation. Once in the soil, microorganisms break down the nitrogen into different forms, which is then taken up by plants. Nitrogen eventually makes its way back into the atmosphere.

Question

What would happen within the nitrogen cycle if a bactericide, a substance that kills bacteria, was added to the soil?

More nutrients would be added to the soil, increasing the amount of nitrogen available to plants.

The rate at which nitrogen is broken down would increase, resulting in faster absorption by plants.

Microorganisms would not be present to break down the nitrogen into a usable form for plants.

Nitrogen would be blocked from entering the soil, making it unavailable for plants to use.

Answer 1

If a bactericide, which kills bacteria, was added to the soil, the outcome would primarily be that microorganisms would not be present to break down the nitrogen into a usable form for plants.

Bacteria play a crucial role in the nitrogen cycle, particularly in processes such as nitrogen fixation, nitrification, and denitrification. These processes convert nitrogen into forms that plants can absorb and utilize. If a bactericide kills the bacteria responsible for these processes, nitrogen in the soil would remain in forms that are unavailable to plants, thereby disrupting the nitrogen cycle and potentially limiting plant growth due to insufficient nitrogen.

The other options presented are incorrect:

• Adding more nutrients would not occur; instead, the availability of nitrogen would decrease.
• The rate at which nitrogen is broken down would not increase; in fact, it would decrease due to the loss of bacterial activity.
• Nitrogen would not be blocked from entering the soil; rather, its conversion to usable forms would be inhibited.