Which of the following factors is NOT required for denitrification to occur?

Denitrification is a critical process in the nitrogen cycle, where nitrate is reduced to nitrogen gas or other nitrogen oxides, which are then released into the atmosphere. This process generally occurs under anaerobic conditions, meaning that the soil must be saturated with water, limiting the availability of oxygen.

Organic matter plays a significant role in denitrification as it provides the necessary carbon source for denitrifying bacteria. Nitrate nitrogen is also essential, as denitrification specifically involves the transformation of nitrates into nitrogen gas.

Chelated metals, however, are not a necessary component for denitrification to take place. While specific metal ions can sometimes facilitate microbial processes, they do not directly contribute to the fundamental biochemical reactions involved in denitrification. Therefore, the correct choice is that chelated metals are not required for denitrification to occur.