Investigators: Lloyd Murdock, Ken Wells, Tom Mueller, Paula Howe, and Bill Craddock

Yield monitors have made it possible for farmers to measure yield variability of corn and soybeans within specific field boundaries. Attempts to date to relate such yield variability to fertility variation in the surface 10 to 15 cm (4 to 6 inches) layer of soil have not been successful, implying that soil factors other than surface fertility level variation may be exerting more influence on yields. Therefore the objective of this study is to more precisely map soil morphological characteristics, both on a horizontal scale and a vertical scale, and then determine if such variability is associated with yield variability of corn and/or soybeans. This information should be useful in identifying management changes that might improve yields or reduce production costs in low-yielding areas of a field.

This work will be conducted on farm fields where at least three years of yield maps are available. Two sites will be selected, one representative of the Western Pennyroyal Area, and one representative of the Outer Bluegrass Area. Soils on these landscapes are widely used for production of corn, wheat, and soybeans. Specific fields at each site will be identified from existing three-year yield map history where yield variability has been consistent in the same areas of the field from year-to-year. Once identified, USDA-NRCS soil scientists will prepare detailed soils maps of appropriate areas within the fields. These maps will provide detailed soil type information such as horizonation types and thickness, texture, internal drainage, rooting depth, and any other notable characteristics that may affect plant growth. Additionally, soil samples will be taken, as appropriate, to measure acidity, nutrient, and organic matter levels. The database developed from this three-dimensional definition of soil characteristics will be used to develop GIS maps that can then be layered over existing corn and/or soybean yield maps to determine the relationship between yields and soil characteristic variability.

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