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Interpretive Summaries:
Assessment of Alfalfa Yield Monitoring Technology to Improve Nutrient Use Efficiency, 2011
Yield mapping has been beneficial by demonstrating the degree of yield variability in areas much smaller than whole fields. Although growers recognize this variability, it is difficult to measure and map without a yield monitor. Grain crops have led the way with yield monitoring technology, which is not widely used or is still under development for many other important crops. In other crops like alfalfa the technology has not even existed until recently. Using bale sampling and tissue testing and then noting the bale locations with a GPS, hay quality and crop nutrition status can be linked with yield data for specific locations in the field. Overall, we expect that the use of yield monitoring data can significantly increase fertilizer use efficiency by meeting specific crop needs, increase hay yield and quality, and reduce potential P and K losses to the environment.
In order to assess the accuracy of an experimental yield monitor, biomass samples were collected from three windrows and weighed during the fifth cutting of one alfalfa field, and compared with yield monitor values. Management zones were created based on the previous cutting yield maps, where high yielding and low yielding zones had been established. The comparison of biomass samples and yield monitor values consisted of comparing sections of the alfalfa windrow to the closest bale weight from the yield monitor.
Although the alfalfa yield monitor was simple to install and operate, a considerable amount of data was lost during the baling processes due to different reasons related to equipment malfunction. Of the three fields monitored, we were unable to collect whole field data for any of them for all the five cuttings during the 2011 growing season. This fact made it difficult to advance to the next step of the project: defining management zones and assess the yield monitor accuracy.
Overall, the yield maps created with the yield monitor were able to show clear yield differences in different parts of the fields, which were confirmed by the grower. However, the biomass weight comparison between the yield monitor and the tarp method showed an unacceptably large difference in dry yield (over 30%). Therefore, we expect to investigate the possible causes of the yield monitor’s lack of accuracy during the 2012 growing season and attempt to meet the original objectives. CA-30
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