Using Electrical Conductivity Classification and Within-Field Variability to Design Field-Scale Research

• Published in: Agronomy journal 2003-05, Vol.95 (3), p.602-613
• Main Authors: Johnson, C.K, Eskridge, K.M, Wienhold, B.J, Doran, J.W, Peterson, G.A, Buchleiter, G.W
• Format: Article
• Language: English
• Subjects: agricultural soils; Agronomy. Soil science and plant productions; Biological and medical sciences; crop rotation; electrical conductivity; estimation; experimental design; experimental error variance; field experimentation; fields; Fundamental and applied biological sciences. Psychology; Generalities. Biometrics, experimentation. Remote sensing; Generalities. Information. Documentation. Research; Panicum miliaceum; spatial variation; Triticum aestivum; variance; winter wheat; within-field variance; Zea mays
• ISSN: 0002-1962; 1435-0645; 1435-0645
• DOI: 10.2134/agronj2003.0602

Agronomic researchers are increasingly accountable for research programs and outcomes relevant to producers. Participatory research--where farmers assume leadership roles in identifying, designing, and managing on-farm field-scale research--addresses this directive. However, replication is often unfeasible at this level of scale, underscoring a need for alternative methods to estimate experimental error. We compared mean square errors to evaluate: (i) within-field variability for estimating experimental error (in lieu of replication) and (ii) classified within-field variability, using apparent electrical conductivity (ECa), for estimating plot-scale experimental error. Eight 31-ha fields, within a contiguous section of farmland (250 ha), were managed as two replicates of each phase of a no-till winter wheat (Triticum aestivum L.)-corn (Zea mays L.)-millet (Panicum miliaceum L.)-fallow rotation. The section was ECa-mapped (approximately 0- to 30-cm depth) and separated into four classes (ranges of ECa). Georeferenced sites (n = 96) were selected within classes, sampled, and assayed for multiple soil parameters (0- to 7.5- and 0- to 30-cm depths) and residue mass. Within-field variance effectively estimated experimental error variance for several evaluated parameters, supporting its potential application as a surrogate for replication. Comparison of data from the field-scale experimental site to that from a nearby plot-scale experiment revealed that ECa-classified within-field variance approximates plot-scale experimental error. We propose using this relationship for a systems approach to research wherein treatment differences and their standard errors, derived from ECa-classified field-scale experiments, are used to roughly evaluate treatments and identify research questions for further study at the plot scale.