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Screening Yield Monitor Data Improves Grain Yield Maps

Dep. of Agron. and Hortic., Univ. of Nebraska, P.O. Box 830915, Lincoln, NE 68583-0915

View larger version (34K): [in a new window]   Fig. 1. Algorithm for yield data screening in which six types of erroneous or uncertain values are deleted.

View larger version (22K): [in a new window]   Fig. 2. Effect of different grain flow shift values (delay time) on the ratio of surface area of a 3-d plot of the yield monitor data to projected area of the upper surface. Optimum selection of a grain flow shift value occurs when this ratio is at a minimum.

View larger version (40K): [in a new window]   Fig. 3. Grain flow measured by the yield monitor near the start or end of harvest passes. The different symbols show 15 harvest passes in each field, which were used to derive the values for start-/end-pass delays in Step 2 of the screening algorithm shown in Fig. 1.

View larger version (14K): [in a new window]   Fig. 4. Determination of local neighborhood outliers (Step 5 in Fig. 1). The dotted circle shows the yield data point xj being tested. An estimated yield is calculated by inverse distance interpolation from the yield points located within the local neighborhood and compared with the actual yield. Arrows indicate the direction of the different combine passes in this example.

View larger version (39K): [in a new window]   Fig. 5. Sequential removal of erroneous or uncertain yield data in the six screening steps: (1) header status up; (2) start-/end-pass delays; (3) grain flow, distance traveled, and grain moisture outliers; (4) minimum/maximum yield limits; (5) local neighborhood outliers; (6) short segments and co-located points. Values refer to irrigated and rainfed maize (Fields A and B, respectively) and irrigated and rainfed soybean (Fields C and D, respectively).

View larger version (76K): [in a new window]   Fig. 6. Yield monitor data before screening (left) and all removed points (right) in irrigated and rainfed maize (Fields A and B, respectively) and irrigated and rainfed soybean (Fields C and D, respectively).

View larger version (37K): [in a new window]   Fig. 7. Experimental semivariograms and fitted double-exponential variogram models of grain yield after primary and secondary yield monitor data screening. In each graph, fitted variogram parameters after primary screening are shown in the top left corner while those on the lower right corner show the variogram parameters after secondary screening.