importance of carbon dioxide and importance of ammonia
Read, read, read, and take good notes.
http://www.google.com/search?q=importance+of+carbon+dioxide+in+agriculture&oq=importance+of+carbon+dioxide+in+agriculture&aqs=chrome..69i57.8344j0j7&sourceid=chrome&espv=210&es_sm=122&ie=UTF-8
http://www.google.com/search?q=importance+of+ammonia+in+agriculture&oq=importance+of+ammonia&aqs=chrome.4.69i57j0l5.3481j0j7&sourceid=chrome&espv=210&es_sm=122&ie=UTF-8