Submitted to: Soil Science Society of America Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: December 12, 1997
Publication Date: N/A
Interpretive Summary: Farmers and agricultural managers need methods to characterize the spatial variability of soil properties and to know how this variability affects crop yield. Farmers can now map crop yield in great detail but it is difficult to interpret those maps without other information. Techniques are needed to interpret yield maps in terms of soil variability and develop site-specific management practices based on the variability. In this study we intensively sampled corn grain yields on a hillslope in Central New York over a period of three years. We also measured elevation. We found that yield variability was most strongly related to surface undulations in the topography and rooting depth. We calculated a value for surface curvature using elevation data that indicated whether the slope was concave (positive curvature) or convex (negative curvature). Yields were related to this value of curvature. Variability in grain yield from year to year was largest where the land surface was strongly concave or convex. Curvature affected yield through its influence on water availability. Yields were also related to the depth to a root restricting layer where lower yields were associated with more shallow depths. We found little relationship between the spatial variability of phosphorus and potassium, and corn grain yield. We concluded that factors that influence water availability have a greater impact on the variability of corn yield than fertility in a well fertilized field. Based on the results of this work elevation maps can be useful in delineation of management zones on a complex hill slope by separation of areas with low curvature from areas with high curvature.
Crop yields can now be mapped in detail and techniques are needed to interpret yield maps in terms of soil variability, and to develop site-spec management practices based on the variability. Soil properties and crop yields can be highly variable on complex hillslopes. The purpose of this study was to examine the temporal and spatial variability of corn grain yield on a typic Fragiochrept soil on a hill slope. Corn (Zea Mays L.) grain yields were intensively sampled during 3 growing seasons from a field that measured 280 X 150 m. Soil surface elevation, soil organic matter, P, and K contents were also measured. Grain yield data and topography were analyzed by statistical methods designed to analyze space series. Yield variability was most strongly related to surface undulations in the topography and the value of surface curvature was found to be a useful measure of small scale variations in topography. The year to year variations in yield were largest where the curvature was large. Where the curvature was small, the patterns of the yield variation along transects were similar for the two years. Yields did not correlate with soil chemical properties but did correlate with depth to fragipan and percentage organic matter. The yield maps did not show consistent variation from year to year except for one or two locations possibly due to the scale at which the yields were measured. Yield maps may only be useful when used with associated information on soil water holding properties and when dense measurements are collected. Elevation maps, however, can be useful in delineation of management zones on a complex hill slope by separation of areas with low curvature from areas with high curvature.