Submitted to: Agronomy Abstracts
Publication Type: Abstract Only
Publication Acceptance Date: October 7, 1999
Publication Date: N/A
Technical Abstract: Measurement of nutrient availability in precision agriculture has focused primarily on grid-based soil sampling. This study investigated the relationship of spatially-variable grain nutrient concentrations to soil and landscape properties, and compared nutrient removal using yield map data and either spatially-measured concentrations or a soil-specific constant value. Grain phosphorus (P) and potassium (K) concentrations were determined on corn (Zea maize [L.]) and soybean [Glycine max (L.)] crops grown on claypan-soil fields and plots. Spatial structure was evident for both grain P and K concentrations. P concentrations ranged from 2.2 to 3.1 g/kg, while K concentrations ranged from 2.4 to 3.7 g/kg. K removal from a field was over-estimated by as much as 30% using the soil-specific constant value approach. Plot studies revealed pH, topsoil thickness above the claypan, and elevation as the soil and landscape parameters that most consistently helped explain variation in corn grain P and K concentrations Reliance on yield mapped data to predict nutrient removal and subsequent fertilizer applications is questionable on claypan soils without considering spatial variation in grain nutrient concentrations.