title: Soil Parameter Mapping and Ad Hoc Power Analysis to Increase Blocking Efficiency Prior to Establishing a Long-Term Field Experiment.
abstract: The spatial heterogeneity of soil and weed populations poses a challenge to researchers. Unlike aboveground variability, below-ground variability is more difficult to discern without a strategic soil sampling pattern. While blocking is commonly used to control environmental variation, this strategy is rarely informed by data about current soil conditions. Fifty georeferenced sites were located in a 0.65 ha area prior to establishing a long-term field experiment. Soil organic matter (OM) and weed seed bank populations were analyzed at each site and the spatial structure was modeled with semivariograms and interpolated with kriging to map the surface. These maps were used to formulate three strategic blocking patterns and the efficiency of each pattern was compared to a completely randomized design and a west to east model not informed by soil variability. Compared to OM, weeds were more variable across the landscape and had a shorter range of autocorrelation, and models to increase blocking efficiency resulted in less increase in power. Weeds and OM were not correlated, so no model examined improved power equally for both parameters. Compared to the west to east blocking pattern, the final blocking pattern chosen resulted in a 7-fold increase in power for OM and a 36% increase in power for weeds.
authors.affiliation: Center for Sustaining Agriculture and Natural Resources, Washington State University, 2606 W Pioneer, Puyallup, WA 98371, USA.
authors.forename: Doug
authors.initials: D
authors.lastname: Collins
authors.affiliation: Washington State University Extension, 1000 N Forest Street, Suite 201, Bellingham, WA 98225, USA.
authors.forename: Chris
authors.initials: C
authors.lastname: Benedict
authors.affiliation: Washington State University Crop and Soil Sciences, 2606 W Pioneer, Puyallup, WA 98371, USA.
authors.forename: Andy
authors.initials: A
authors.lastname: Bary
authors.affiliation: Washington State University Crop and Soil Sciences, 2606 W Pioneer, Puyallup, WA 98371, USA.
authors.forename: Craig
authors.initials: C
authors.lastname: Cogger
mesh_terms: D000383:Agriculture / Q000379:methods*; D009930:Organic Chemicals / Q000032:analysis; D057685:Plant Weeds / Q000737:chemistry; D012987:Soil / Q000737:chemistry*; D013223:Statistics as Topic; D013997:Time Factors
chemical_list: D009930:Organic Chemicals; D012987:Soil