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SITE-SPECIFIC MANAGEMENT

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

^* Corresponding author (cjohnso2{at}bigred.unl.edu)

Received for publication November 14, 2001. Site-specific management (SSM) can potentially improve both economic and ecological outcomes in agriculture. Effective SSM requires strong and temporally consistent relationships among identified management zones; underlying soil physical, chemical, and biological parameters; and crop yields. In the central Great Plains, a 250-ha dryland experiment was mapped for apparent electrical conductivity (EC_a). Eight fields were individually partitioned into four management zones based on equal ranges of deep (EC_DP) and shallow (EC_SH) EC_a (approximately 0–30 and 0–90 cm depths, respectively). Previous experiments documented negative correlations between EC_SH and soil properties indicative of productivity. The objectives of this study were to examine EC_SH and EC_DP relationships with 2 yr of winter wheat (Triticum aestivum L.) and corn (Zea mays L.) yields and to consider the potential applications of EC_a–based management zones for SSM in a semiarid cropping system. Within-zone wheat yield means were negatively correlated with EC_SH (r = -0.97 to -0.99) and positively correlated with EC_DP (r = 0.79–0.97). Within-zone corn yield means showed no consistent relationship with EC_SH but positive correlation with EC_DP (r = 0.81–0.97). Equal-range and unsupervised classification methods were compared for EC_SH; within-zone yield variances declined slightly (0–5%) with the unsupervised approach. Yield response curves relating maximum wheat yields and EC_SH revealed a boundary line of maximum yield that decreased with increasing EC_SH. In this semiarid system, EC_SH–based management zones can be used in SSM of wheat for: (i) soil sampling to assess residual nutrients and soil attributes affecting herbicide efficacy, (ii) yield goal determination, and (iii) prescription maps for metering inputs.

Abbreviations: EC_a, apparent electrical conductivity • EC_DP, deep apparent electrical conductivity • EC_SH, shallow apparent electrical conductivity • GIS, geographic information system • SSM, site-specific management

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