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Management, Topographical, and Weather Effects on Spatial Variability of Crop Grain Yields

^a Dep. of Crop and Soil Sci., Michigan State Univ., East Lansing, MI, 48824-1325
^b W.K. Kellogg Biol. Stn. and Dep. of Crop and Soil Sci., Michigan State Univ., Hickory Corners, MI 49060-9516

View larger version (88K): [in a new window]   Fig. 1. Layout of the first five replications (blocks) of the experimental site with locations of the elevation measurements, locations of the experimental plots from the four treatments used in the study, and the 15- by 15-m interpolated elevation map. The plots are labeled with the last two letters from their treatment names and respective replication numbers, e.g., T2-R1 is the plot from Replication 1 that received treatment NoTillConv-T2. Inclusion represents an example of yield data points collected from each experimental plot via combine monitor.

View larger version (25K): [in a new window]   Fig. 2. Average daily precipitation values for the period March–June of the studied years.

View larger version (12K): [in a new window]   Fig. 3. Example of a general relative variogram calculated for the 1996 corn yield data from the Replication 3 plot of ChiselNoChem-T4 treatment. Variogram slope near origin (0.0191) was obtained by fitting linear regression line (solid line) to the variogram values at the first three lag distances. Variogram value at the shortest lag distance (Var1.5) is marked with an open circle.

View larger version (111K): [in a new window]   Fig. 4. Coefficient of variation for crop yields (yijk) as a function of terrain slope (T) and average daily precipitation in April–June (W) in (a) ChiselConv-T1, (b) NoTillConv-T2, and (c) ChiselNoChem-T4. The results were not significant for ChiselLow-T3 (not shown). Effect of terrain slope (T) was not significant for NoTillConv-T2 and hence is not included.

View larger version (20K): [in a new window]   Fig. 5. General relative variograms for 1998 wheat yield from the five experimental plots of ChiselConv-T1 treatment and six experimental plots of the ChiselNoChem-T4 treatment.

View larger version (46K): [in a new window]   Fig. 6. Integral scale(yijk) as a function of terrain slope (T) and average daily precipitation in April–June (W).