Levi Hilton and Dr. Byron Adams, Microbiology
A geographic information system (GIS) is a powerful tool for correlating information that has a spatial component. This technique has been used in many different ways from organizing major corporations and services to building intricate maps. We used a GIS to help determine if there was a certain type of soil that can be correlated to specific nematode species which are used as organic pesticides in agriculture.
Dr. Byron Adams and his colleagues from Florida University proposed the hypothesis that certain entomopathogenic nematode species would show specificity according to soil type. In the summer of 2001 they set out collecting hundreds of soil samples from many citrus groves and their surrounding sites. These sample sites were documented and a geographic reference point was taken at each using a GPS system. It was hoped that these sample sites would contain the nematode species Steinernemia and Heterorabditis. These two species are the most commonly used entomopathogenic (parasitic towards other plant parasites) species commercially. If a spatial correlation could be found it would prove beneficial to the farming community that employs this technique.
This is where my part came in. I had the task of organizing and creating a GIS that plotted the sites out on a map that showed the different soil types of Florida. The program we used was called ArcView from the company ESRI. It took me a while to become proficient enough to use the program; I had some help from the geography department at BYU.
There were many initial attempts at creating a useable map that failed. I had a really hard time getting the points to match up over the right map. Our big break came when Dr. Adams contacted a fellow colleague that does a lot of GIS work. He directed us to the USDA where we obtained a map of Florida, already in a GIS format, that outlined the different types of soils in the state. Using this map we had to get the two to layout on top of each other correctly. Using tools and databases provided by ArcView the two were correctly correlated and the following figure was obtained Fig 1.
This is a specific area of the map that was the most statistically significant. Most of the other soil specific areas only had one or two sample sites and weren’t statistically interesting. There appears to be a significant contrast between the soil type designated by the color blue and the neighboring soil type in green. The blue had two hits out of eighteen sample sites whereas the green area had eight out of twelve hits. This is very statistically interesting especially since these two soil types are so close to each other. We tried to establish which soil types these two were but the USDA was charging an amount for the information that was beyond the scope of this project. Regardless, this leads us to believe that nematodes might have a soil type affinity.
This project was only a preliminary step in determining whether or not entomopathogenic nematode species show affinity for certain soil types. The next step will be to go back to Florida and further test these statistically interesting sites. My research was presented at the Society of Nematology annual conference summer 2004. Some of my results are currently being published in a paper by Dr. Adams and his associates. I feel that this has been a major stepping stone in my academic and professional career. Hopefully this research will aid in developing more effective means of crop production and application of nematodes as a pesticide.