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March 23, 2006
Geospatial Applications: Learning About Variable-rate Fertilizer Application
Judging from the number of telephone calls and e-mail requests I receive for information about how to make fertilizer prescription maps, it is likely an increasing number of farmers are varying the amount of fertilizer applied across fields this year. Farmers use the global positioning system (GPS), coupled with other technologies, to refine their crop fertility practices. Instead of applying a uniform fertilizer rate throughout a field, with the use of GPS and variable-rate application equipment, farmers are experimenting with spatial management practices and varying crop yield goals within fields. Given the historically high nitrogen fertilizer prices, these farmers are attempting to make more efficient use of the fertilizer applied to each field by dividing fields into management zones. Farmers starting to use variable-rate fertilizer application have several tasks to accomplish before they get to the field. Acquiring equipment capable of varying fertilizer inputs, although the most expensive step, is usually not the most difficult task. The most common questions I receive relating to this technology are how to make variable rate maps, how to get those maps in a format that the equipment controllers will accept and how to work between brands of equipment. Making variable maps requires a geographic information systems (GIS) computer program and valid information to reliably divide fields into zones for variable-rate application. GIS programs are used to combine information to develop management zones and variable rate application maps (often called prescription maps). Prescription maps are used in fertilizer application controllers, which are really computers, installed in the tractor cab. These onboard computer/controllers send map and GPS information to the variable-rate controller on the fertilizer application equipment. The equipment then varies the amount of fertilizer applied at different locations across the field. This process requires a computer GIS program and the skills to use it. Some fertilizer supply companies sell this service on a per-acre basis. Several GIS computer programs, including general GIS programs such as ArcView, MapInfo and Farm Works, are available to make variable-rate application maps. Most of the major agricultural equipment companies sell GIS programs that are specifically written for farm applications. I recommend using one of the GIS programs specifically developed for farms. I encourage individuals to take the time to learn what kind of GIS programs are available, the costs involved and the skill required to use them. The NDSU Extension Service regularly schedules GIS workshops across North Dakota. Anyone interested in more information or training opportunities can contact their county Extension office to ask staff to assist in scheduling training in your area. Other agencies also provide training in this technology. The Upper Midwest Aerospace Consortium (UMAC) at the University of North Dakota is providing training to farmers, ranchers, crop consultants and others who want to learn more about geospatial technology applications in agriculture. These daylong training programs are scheduled for March 24, 29 and 31.The training includes presentations by farmers who are successfully using the technology and a hands-on computer lab tutorial using imagery of participants’ land where possible. A $25 registration fee covers breakfast and lunch charges. The training sessions will be held from 8:30 a.m. to 5 p.m. in Streibel Hall, Room 107, at the UND Aerospace complex on University Avenue and Campus Road in Grand Forks. For more information about the UND seminars or to register, contact UMAC administrative secretary Kathy Ebertowski at (701) 777-2940 or e-mail kaeberto@aero.und.edu. The companies and individuals selling variable-rate application equipment are the best source for technical support for their brand of equipment. However, many farmers use more than one brand of equipment and find that moving maps and digital data from one brand to another often presents problems. Farmers need to ask these technical representatives what kind of map file formats each brand will accept. The most common map file type for exchanging maps between brands is a shapefile, although some equipment controllers will not accept this format, either. The file extension for shapefiles is .shp. It is important to resolve the digital problems before using the equipment in the field. ### Source: John
Nowatzki, (701) 231-8213, jnowatzk@ndsuext.nodak.edu |
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North Dakota State University |
