Submitted to: Agronomy Abstracts
Publication Type: Abstract Only
Publication Acceptance Date: October 7, 1999
Publication Date: N/A
Technical Abstract: Current variable-rate fertilizer strategies rely mainly on maps made from grid-soil sampling. Many other non-nutrient factors also impact crop productivity. The objective of this research was to develop and validate an improved method for site-specific fertilizer recommendations. Variable-rate N, P, K, and lime plans were developed for two claypan soil fields in Missouri. Fields were yield mapped, grid- soil sampled, topography surveyed, and topsoil-depth surveyed (using electromagnetic induction) in 1995-96. Evaluation of measurements was conducted on sub-field areas delineated by relative elevation and EM-sensed topsoil depth to develop fertilizer recommendations. This approach uses apparent plant-available water capacity and landscape water redistribution as the predominating factors influencing crop productivity. Fields were planted using site- specific management (SSM), with embedded strips of conventional management (CM) for comparison. Corn yields from SSM have generally been similar to yields from CM where topsoil was shallow. Where topsoil was greater than 60 cm, SSM significantly out-yielded CM. Soybean yield variation has not been different between the two management systems.