TY - JOUR
T1 - Apparent soil electrical conductivity
T2 - Applications for designing and evaluating field-scale experiments
AU - Johnson, C. K.
AU - Eskridge, K. M.
AU - Corwin, D. L.
N1 - Funding Information:
The authors wish to acknowledge the University of California Kearney Foundation of Soil Science and the University of California Salinity-Drainage program for the funds that supported the chemical analyses of the soil core samples. Ceil Howe, Jr., and Ceil Howe III provided the site. The authors thank Nahid Vishteh and Harry Forster for their analytical technical support, James Wood for his help in collecting soil core samples, and especially acknowledge the conscientious work and diligence of Clay Wilkinson and Derrick Lai who performed the preparation and chemical analysis of the soil samples. Thanks are also extended to Scott Lesch for technical expertise and assistance with EC a classification of the Westlake Farms site.
PY - 2005/3
Y1 - 2005/3
N2 - On-farm field-scale research has become increasingly common with the advent of new technologies. While promoting a realistic systems perspective, field-scale experiments do not lend themselves to the traditional design concepts of replication and blocking. Previously, a farm-scale dryland experiment in northeastern Colorado was conducted to evaluate apparent electrical conductivity (ECa) classification (within-field blocking) as a basis for estimating plot-scale experimental error. Comparison of mean-square (MS) errors for several soil properties and surface residue mass measured at this site, with those from a nearby plot-scale experiment, revealed that ECa-classified within-field variance approximates plot-scale experimental error. In the present study, we tested these findings at a second and disparate experimental site, Westlake Farms (WLF) in central California. This 32 ha site was ECa mapped and partitioned into four and five classes using a response-surface model. Classification based on ECa significantly delineated most soil properties evaluated (0-0.3 and/or 0-1.2 m) and effectively reduced MS error (P ≤ 0.10). The MS's for several soil properties evaluated at the site were then compared with those of an associated plot-scale experiment; most MS's were not significantly different between the two levels of scale (P ≤ 0.05), corroborating results from the Colorado experiment. These findings support the use of within-field EC a-classified variance as a surrogate for plot-scale experimental error and a basis for roughly evaluating treatment differences in non-replicated field-scale experiments. This alternative statistical design may promote field-scale research and encourage a reversal in research direction wherein research questions identified in field-scale studies are pursued at the plot-scale.
AB - On-farm field-scale research has become increasingly common with the advent of new technologies. While promoting a realistic systems perspective, field-scale experiments do not lend themselves to the traditional design concepts of replication and blocking. Previously, a farm-scale dryland experiment in northeastern Colorado was conducted to evaluate apparent electrical conductivity (ECa) classification (within-field blocking) as a basis for estimating plot-scale experimental error. Comparison of mean-square (MS) errors for several soil properties and surface residue mass measured at this site, with those from a nearby plot-scale experiment, revealed that ECa-classified within-field variance approximates plot-scale experimental error. In the present study, we tested these findings at a second and disparate experimental site, Westlake Farms (WLF) in central California. This 32 ha site was ECa mapped and partitioned into four and five classes using a response-surface model. Classification based on ECa significantly delineated most soil properties evaluated (0-0.3 and/or 0-1.2 m) and effectively reduced MS error (P ≤ 0.10). The MS's for several soil properties evaluated at the site were then compared with those of an associated plot-scale experiment; most MS's were not significantly different between the two levels of scale (P ≤ 0.05), corroborating results from the Colorado experiment. These findings support the use of within-field EC a-classified variance as a surrogate for plot-scale experimental error and a basis for roughly evaluating treatment differences in non-replicated field-scale experiments. This alternative statistical design may promote field-scale research and encourage a reversal in research direction wherein research questions identified in field-scale studies are pursued at the plot-scale.
KW - Agricultural systems
KW - Classified management maps
KW - Geographic information systems
KW - Soil electrical conductivity
KW - Statistical analyses
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U2 - 10.1016/j.compag.2004.12.001
DO - 10.1016/j.compag.2004.12.001
M3 - Article
AN - SCOPUS:13844320985
SN - 0168-1699
VL - 46
SP - 181
EP - 202
JO - Computers and Electronics in Agriculture
JF - Computers and Electronics in Agriculture
IS - 1-3 SPEC. ISS.
ER -