What a GREAT Question! My name is Tracy Ostrom and I am a GLOBE partner and scientists with the University of California at Berkeley. I work iwth students such as yourself in GLOBE investigations and I work with their teachers as well. Your research is incredibly thorough and thank you for your in-depth analysis of fertilizers and crop growth. I did my undergraduate studies in Ohio at Heidelberg and this was a big research topic for us back in the 80s. Nitrogen is so important to the success of our agriculture. Do you know how nitrigen helps plants grow? It's pretty intersting and one reason why fertilzers have so much nitrogen in them. Crop rotation techniques also put nitrogen back into the soil....perhaps a longer addition to your research? I think your presentation of data was very well done, your graphs were very clear and easy to follow. Thank you for taking the time to present your work to us. Soil science is a great way to tie in planst, animals and nutrients. Bravo!