Crop Yield Variation Associated with Coastal Plain Soil Map Units

Abstract

AbstractVariation among soil map units needs to be quantified so farmers can implement more economically and environmentally acceptable production practices. We conducted a 4‐yr field study at an 8‐ha research site near Florence, SC, to quantify yield variation for a southeastern Coastal Plain field. Nineteen soil map units, classified as Ultisols and representing seven soil series were identified by Soil Conservation Service cooperators. Corn (Zea mays L.) was grown in 1985, 1986, and 1988, while in 1987 wheat (Triticum aestivum L.) and grain sorghum [Sorghum bicolor (L.) Moench] were double‐cropped. All soils received conventional disk tillage, fertilization based on soil‐test recommendations, and uniform planting rates. Crop yield was measured by harvesting transects throughout the field and subsequently identifying soil map units for each plot. Average corn yield among soil map units ranged from 3.7 to 8.0 Mg ha−1 in 1985, 0.1 to 2.8 Mg ha−1 in 1986, and 1.1 to 5.0 Mg ha−1 in 1988. Yields were lower in 1986 because of severe drought. Wheat yield ranged from 3.5 to 6.2 Mg ha−1, while sorghum yield ranged from 1.7 to 5.2 Mg ha−1 in 1987. Extractable P, K, Ca, Mg, Mn, and Zn; soil organic matter and pH; and depth to an argillic horizon (Bt) were measured to identify causes for yield variation among soil map units. Depth to Bt had the best statistical relationship between crop yield and soil map unit, but yield variation within an individual map unit was almost as large as variation between map units. Our results demonstrate how measurements of crop yield by soil map unit can be determined and used to study soil variation. They also provide a data base that can be used to evaluate plant growth and soil management models for individual soil map units.