As we learned in our first year, it is posible to use GPS rtk to map the exact path of the planter and to use that record to subsequently guide the cultivator to control weeds. In addition to accurately maping the path of each pass with the planter, we were able to use the GPS rtk to steer the planting tractor straighter and more precisely than we could do with all but the most skilled human operators. This use of GPS technology makes corn planter markers unecesary. Markers for planters ranging from 12 rows up are very expensive componenets that need frequent maintenance. We used Our GPS reciever to guide both an older tractor with trackball steering and a much newer one with internal autosteer.
The GPS rtk performed adequately on both tractors but worked much more smoothly and needed less tending on the tractor with internal steering valves. We encountered several serious problems while opperating the equipment on GPS rtk guidance. The biggest was the need to get immediate technical assitance whenever the GPS unit lost the signal or malfunctioned in any way. There was a period just at dusk each day, when the GPS would often lose its satelite signal and stop working. With prompt technical expertise, the signal could be restored and work resumed but that help was often not available when it’ was most needed. For GPS rtk to be an effective reliable tool for planting and cultivating opperations, at least one person would need to have the proper training and expertise to trouble shoot and fix technical problems with the equipment.
Our goals had been:
– to demonstrate a functioning GPS rtk controled cultivator that used maps recorded at planting to guide the cultivator for weed control operations.
– to use GPS rtk equipment for corecting and maintaning the locations of contour strip and field boundaries. Crop strips are very difficult to keep true from year to year and the edges of strips vary causing gaps and overlaps that waste inputs, lower yields, and result in more weed growth.
– maping/adjusting strip & field edges and sizes with GPS rtk to create field opperations plans that reduce wasted materials, machinery overlaps, and unproductive passes across fields.
While we could not meet our first goal in a way that we are satisfied with, I feel we learned valuable lessons about GPS technology’s limitations and potential. The capabilities of currently available equipment and software is not easily adapted to following the lines recorded from earlier opperations without glitches that are frequent enough to require a high level of technical expertise to be on call at all times. On the other hand, it is very reliable when guiding equipment to follow a theoretical plan such as is needed to keep strip boudaries within a close tolerance needed for eliminating overlaps and wasted trips across fields. The potential payback from reduced wasted iinputs including labor and fuel from GPS is substantial and reliable.
Impacts and Contributions/Outcomes
GPS rtk technology is somewhat like computers were 25 years ago, a powerful tool looking for the most advantgeous way to be used. Some of the first applications are now obsolete while many surprizing other uses have since been developed. Also, the power and capability of computers went up so fast that things that were initialy not possible or practical, are commonplace today. From our initial results, I believe that field mapping, equipment guidance from a planed design, and field operations planning are very profitable uses that currently available GPS technology is adequately developed and very well suited for. The paybacks from saved inputs, higher field efficiencies, and precision soil management are already well understood and can be realized with currently available equipment. Our cultivator guidance plan depends on two separate GPS units. One to guide the tractor acording to a predetermined plan and the other to record the true path of the planter which on rolling topogaraphy, can vary by more than 6 inches from the original plan. Then the recorded data is used to guide the cultivator.
We found that any interuptions or problems with the satelite signals (or the corection signal) even if they only invoved small areas of a field or if they only lasted for a brief period would stop the operation of the machine. If it occured during planting, we could switch to manual steering but that left a gap in coverage of the planting map. These interuptions, no matter how small, made the system too unreliable to depend on as the only guidance system that was used. It also makes it premature for us to recommend or to imply that we recommend the use of this technolgy to other farmers at this time. The general take away insight that we got from our experience is that while GPS rtk guidance of cultivators is possible, it is not yet reliable enough to fully depend on. We have also learned that there are other methods of cultivator guidance that may be closer to being field ready than GPS is at this time. One is a camera system sold by Garford in the UK, that unlike earlier camera systems, uses the recognition of geometric patterns to discern crop rows in the field. This system is already working successfuly on several farms in Europe and a few on the west coast of the US.
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