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Fluid Journal : Fluid Journal 2008-2009
limit yield differences due to different genetics. Identification of zones. A bare soil image (Figure 2) can show differences in soil type and drainage. A prior yield map (Figure 3), can show yield and traffic patterns, locations of headlands, end rows, irrigation systems, and also provides elevation data used to create a topographic map. In-season satellite and aerial images, digital soil maps, GPS soil tests, and tile drainage maps can further delineate management zones. Research design/layout. This research approach uses blocks or "stamps." The stamp placement is determined by evaluating the available spatial layers. The location of the research should be targeted **to provide an even representation from low, medium, and high-performing areas in the field. These stamps are assigned to areas approximately 300 feet long and twice the width of the applicator, with each typically half to one acre in size. The length needs to be adequate to allow the rate controller sufficient time to change from the previous rate and provide a sufficient amount of data points. Selecting a stamp width twice the applicator boom width provides a measure of assurance in case the chosen A-B line of the application equipment does not match up with the intended alignment of the stamp (Figures 4 and 5). The decision to use six stamps in this experiment protocol limited the economic loss to the farmer due to yield reduction in the N-omission areas while providing a statistical amount of data points to develop the yield response function. As-applied data. The actual applied rate of fertilizer can vary from the intended rate of fertilizer prescribed. As mentioned above, this can be due to equipment limitations such as driving too fast for the desired rate, rapid changes in speed or direction, skips, overlaps, machine breakdown, and product flow issues. For these reasons the as-applied map is a vital element in validating the amount of product applied. The difference between the target rate and the actual rate can be used after harvest as a means to select the yield data points matching the desired fertilizer rate. In-season considerations. In-season aerial photography can identify yield-limiting events that have occurred which are beyond the control of the farmer. The imagery can be an important link used to explain unusual crop responses when analyzing the yield data. The imagery can be used to identify weed pressure, storm damage from hail or wind, and drought or flood effects. If an in-season crop protection product is needed such as a fungicide, herbicide, or insecticide, it should be applied to all of the research stamps evenly to eliminate it as a source of variability. Harvest. At the start of each harvest season there are routine adjustments and maintenance for the combine. While making these initial adjustments, it is a good idea to harvest other non-research fields. Calibration loads should be conducted when Figure 5. Overlay of as-applied. Figure 6. Response functions at each site.
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