| | What is precision farming?
It is a new method of farming that tailors inputs of fertilizer, pesticides, etc., to match the variations in growing conditions within a field. The practice is becoming known as Site Specific Management.
Benefits?
Precision farming allows for more efficient use of inputs than does current blanket applications. For example, why waste fertilizer on eroded knolls that don't yield in the best of times? Less fertilizer can also be used in low areas that are already high in fertility, reducing leaching. Not only is precision farming potentially more economical, it should reduce amounts of chemicals released into the environment.
How do you do it?
The idea behind precision farming is to vary fertilizer and pesticide inputs across a field in a predetermined manner. This requires: i) a map of a field which describes how much of an input to apply in various areas, ii) applicators which can vary input rates, and iii) equipment which allows you to know where you are in a field such as Differential Global Positioning Systems (DGPS).
Problems?
While equipment is available to "find yourself" in a field and automatically vary the application of fertilizers or pesticides, our knowledge of the amount of each input we should ideally apply at a specific location isn't yet up to the task. For example, exactly how does wheat on a certain knoll respond to decreased N? This is the most serious problem confronting precision farming. Yield maps are being investigated as a means of solving this problem. Yield maps simply locate where specific yields occur in a field. The idea is that by understanding how yields vary across a field you can determine how to vary the management (although more information than yield will be required to refine input management). One method of creating yield maps is by making use of yield monitors which measure grain flow through a combine, coupled with a DGPS system which creates a continuous stream of yield-position information which can be visually displayed.
Yield map errors
While creating yield maps from yield-position measurements, we've found errors that substantially influence our results. A "through-put" lag occurs between when a crop is straight-cut or picked up and when it registers on the monitor. The lag varies due to changes in combine speed and load. Even after correction for the average lag time it can result in mapped yields being "stretched" by up to 30 meters, although 20 m is more typical. Since adjacent harvest tracks have opposit direction of travel, yield areas can be "stretched" by up to 40m. Other errors include falsely low yields (from varied cutting widths, over-travel areas, and recycling through the tailings return elevator) and falsely high yields (from combine plugging). The result of these and other problems is that some areas of a yield map have more error than others, however, it is difficult to know which areas of the map are wrong. Errors may be "smoothed" out by a computer, but will multiply when used as a basis for management decisions.
Although we are able to trace and reduce many errors, this requires time-consuming processes which may be difficult for a farmer or consultant to accomplish. However, we expect to see improvements in yield monitor-position measurements and their mapping in the near future. In the meantime, the difficulties in knowing where the errors occur lead us to recommend the use of caution in interpreting yield map results, particularly for areas of less than about 40 meters along the combine track. Yield maps should also be compared from year to year to determine if low and high yielding areas are consistent. As precision farming and yield mapping are on the edge of technological improvements to farming, there are problems to work out, but their potential is promising.
For more information contact: Sheilah Nolan . |
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