Using Regionalized Variables to Estimate Field Variability of Corn Yield for Four Tillage Regimes

In selecting an appropriate tillage system for a specific crop and field, it is desirable to choose one that maximizes yield for the field as a whole; however, various areas in a field often give different responses to the same tillage system. The theory of regionalized variables was used to evaluate corn [ Zea mays L.] grain yield response to the following four tillage systems (tandem disking, tandem disking followed by bedding, in‐row‐subsoiling and bedding, and chisel plowing). These treatments were randomized, replicated three times, and stripped across the 198‐m‐long field of Norfolk soil (Typic Paleudults), which had a tillage pan and variable depth to B horizon. Grain was harvested in adjoining 15.2‐m‐long plots in each strip. Analysis of directional semivariograms for relative corn grain yield in the along‐the‐row direction, showed a different variance structure for each tillage treatment. Because only three separation distances were available to compute grain yield semivariance values in the across‐the‐row direction, a composite directional semivariogram in this direction was developed by combining relative grain yield‐semivariance values for all four treatments. A global semivariogram was constructed for each tillage treatment by combining the specific along‐the‐row semivariogram specific for each treatment with the composite across‐the‐row semivariogram, and was used to krige the relative corn grain yield for the entire field for each tillage treatment. Patterns of the kriged yields were appreciably different throughout the field for each tillage treatment. Corn grain yields, estimated using jackknife kriging at each location in the field where grain was harvested, compared favorably with the measured yields for all treatments.