Spatial variability of soybean quality data as a function of field topography: II. A proposed technique for calculating the size of the area for differential soybean harvest

A growing demand for soybeans [Glycine max (L.) Merr.] with high protein and oil concentrations has raised interest in obtaining high quality soybeans using differential harvesting practice. Differential harvesting from the locations with soybeans with higher protein or oil concentrations would be beneficial for producers and for the public who would receive a higher quality product. However, sizes and locations of the areas with high protein or oil concentrations need to be determined prior to harvesting. In this study, we develop a procedure for calculating the size of the area for differential soybean harvesting based on the relationships between protein or oil concentrations and field topography. Range of significant spatial cross-correlation between protein or oil concentrations and elevation as determined by the experimental cross-correlogram is used to calculate effective correlation distance. The effective correlation distance is proposed as an estimate of the size of the area for potential differential harvesting. The effective correlation distance is calculated based on the experimental cross-correlograms between protein or oil concentrations and elevation. Comparison of the experimental cross-correlograms and elevation variograms has shown that the range of the significant spatial cross-correlation between protein or oil concentrations and elevation and, hence, the effective correlation distance, are related to the changes in shape of the elevation variograms. Therefore, the effective correlation distance or the size of the area for differential soybean harvesting can be approximated based on the shape of the elevation variogram.