Crop Yield Interpretation for North Dakota: II. Field Questionnaires—A Delphi Approach

Abstract

A two‐stage Delphi survey was used to evaluate soil productivity indexes currently used for Hard Red Spring (HRS) wheat (Triticum aestivum L.) in North Dakota. Experienced field soil scientists estimated the relative productivity of several soils having a wide range of properties. Mean productivity index for most soils changed little between the first and second questionnaires, but coefficient of variation (CV) decreased an average of 20 and 17% for wheat and sunflower, respectively. Soils with the highest yield variability for both wheat and sunflower were Entic Haploborolls and Typic Ustorthents on upper slopes, Natriborolls, and coarse‐textured or loamy soils with sand and gravel substrata. Results were compared to current productivity indexes and effects of slope, paralithic beds, and argillic horizons evaluated. The Delphi technique proved useful for accessing a source of information based on years of field observation. Relative yield estimates from field soil scientists were particularly useful in evaluating the yield potential of soils for which research data were not available. Delphi surveys should be viewed as a subjective method of investigating soil‐crop yield relationships and used only to supplement quantitative data.

Crop Yield Interpretation for North Dakota: I. Sequential Sampling

“…Results generally support field observations by soil scientists (Ulmer and Patterson, 1988b) and current USDA‐SCS productivity indexes (Tables 2 and 3).…”

Crop Yield Interpretation for North Dakota: III. Long-Term Empirical Models

“…Use of sequential sampling and field questionnaires to collect crop yield data for development of soil productivity indexes were previously discussed (Ulmer and Patterson, 1988a, 1988b). Experiment station research plots represent another source of data useful in yield interpretation.…”