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Site-Specific Management Zones Based on Soil Electrical Conductivity in a Semiarid Cropping System

^a USDA-ARS, 120 Keim Hall, Lincoln, NE 68583-0934
^b Dep. of Crop and Soil Sci., Pennsylvania State Univ., 116 ASI Building, University Park, PA 16802

View larger version (125K): [in a new window]   Fig. 1. Experimental layout superimposed on the March 1999 shallow (approximately 0–30 cm depth of measurement) apparent electrical conductivity map of the 250-ha site. Field numbers, followed by cropping treatments—winter wheat (W), corn (C), proso millet (M), and fallow (F)—for 1998 and 1999 (in parenthesis) are shown in the upper left-hand corner of each field.

View larger version (152K): [in a new window]   Fig. 2. A gray-scale shallow (approximately 0–30 cm depth of measurement) apparent electrical conductivity map for (A) Field 1 and (B) following unsupervised classification and recoding into four electrical conductivity management zones. Variations in color, from dark to light, correspond to increasing conductivity, and symbols represent selected soil-sampling sites.

View larger version (192K): [in a new window]   Fig. 3. Classified apparent electrical conductivity (ECa ) map (applying the unsupervised classification method to 0–30 cm depth of ECa measurement) and soil-sampling scheme for the 250-ha experimental site.

View larger version (26K): [in a new window]   Fig. 4. Mean wheat and corn yields for 1999 and 2000 within management zones based on unsupervised and equal-size classification of shallow electrical conductivity (ECSH) (approximately 0–30 cm depth of measurement) regressed against mean ECSH within ECSH zones. The error bars represent the standard error of the mean.

View larger version (27K): [in a new window]   Fig. 5. Wheat yield frequency distributions for shallow (approximately 0–30 cm depth of ECa measurement) apparent electrical conductivity classes with unsupervised and equal-size classification methods. The black arrows indicate mean yield within ECa classes.

View larger version (17K): [in a new window]   Fig. 6. A) Scatter plot of 1999 winter-wheat yield as a function of shallow (approximately 0–30 cm depth of measurement) apparent electrical conductivity. B) Potential winter wheat yield as a function of shallow apparent electrical conductivity.