What percentage of the air is made up of nitrogen?

What is nitrogen gas in the air converted to?

What is used to convert nitrogen gas into nitrate compounds?

What also converts nitrogen gas in the air to nitrate compounds?

What process converts nitrogen gas into ammonia?

What is ammonia converted to?

What is used to convert ammonia to nitrates?

Where is nitrifying bacteria found?

What absorbs nitrates from the soil?

What do plants use nitrates for?

What is animal protein?

What are decomposers?

What returns nitrogen back to the soil?

How is nitrogen returned to the soil?

Once ammonia is returned to the soil, what is it converted to?

What is used to convert ammonia to nitrates when returning it to the soil?

What can denitrifying bacteria also to?

When does denitrifying bacteria return nitrogen gas back to the air?

What process reduces the amount of nitrogen gas returned to the air?

What does improving drainage do?

How can farmers increase the nitrate content of soil?

How can farmers increase the nitrate content of soil?

What is the definition of crop rotation?

Which of the following is an example of a natural fertiliser?

Which of the following is an example of a natural fertiliser?