Site-specific management zones based on soil electrical conductivity in a semiarid cropping system

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 (ECa). Eight fields were individually partitioned into four management zones based on equal ranges of deep (ECDP) and shallow (ECSH) ECa (approximately 0-30 and 0-90 cm depths, respectively). Previous experiments documented negative correlations between ECSH and soil properties indicative of productivity. The objectives of this study were to examine ECSH and ECDP relationships with 2 yr of winter wheat (Triticum aestivum L.) and corn (Zea mays L.) yields and to consider the potential applications of ECa based management zones for SSM in a semiarid cropping system. Within-zone wheat yield means were negatively correlated with ECSH (r = -0.97 to -0.99) and positively correlated with ECDP (r = 0.79-0.97). Within-zone corn yield means showed no consistent relationship with ECSH but positive correlation with ECDP (r = 0.81-0.97). Equal-range and unsupervised classification methods were compared for ECSH; within-zone yield variances declined slightly (0-5%) with the unsupervised approach. Yield response curves relating maximum wheat yields and ECSH revealed a boundary line of maximum yield that decreased with increasing ECSH. In this semiarid system, ECSH-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.