Designing field studies in soil science

Abstract

Field research in soil science ranges from modal profile descriptions in support of soil survey to elaborate manipulative experimental designs. All of these field approaches make a valuable contribution to soil science, but researchers who do not use either classical manipulative experimental or geostatistical designs have little guidance (or encouragement) available to them. Well-designed field research of any type requires a clear definition of the research question; a thorough review of the literature to establish the state of knowledge; definition of the population under study and the elements that comprise it; and choice of appropriate scales for sampling support, spacing, and study extent based on an understanding of the underlying processes. For studies where hypothesis testing is appropriate, the hypotheses should be based on sound biological or physical reasoning, and sufficient replicates should be taken to ensure a reliable test. The major challenge in field research design is the development of landscape-scale research designs to examine complex interactions among hydrological, climatic, chemical, and biological processes at scales relevant for environmental management. Key words: Research design, landscape-scale , soil genesis, pattern studies, hypothesis testing, spatial statistics, sampling, cesium

Advances in landscape-scale soil research

“…The scale at which this research should be conducted is malleable -the main consideration is that the scale of the study must correspond to the scale of the lateral transport processes being considered (Pennock, 2004;Veldkamp et al, 2001). For example, tillage translocation results in widespread surface modification of soils but the transport distances are often short and little if any off-field deposition occurs; hence the continuum of loss and deposition can be examined within a single field.…”

Nutrient concentrations in roots, leaves and wood of seedling and mature sugar maple and American beech at two contrasting sites

“…We studied sugar maple and American beech in two adjacent catchments in the Adirondack region of New York State, USA, which differ in parent material and soil chemistry, but are similar in other environmental factors affecting tree growth (Christopher et al, 2006). This experimental design allows us to compare tissue chemistry by species between our two sites, but not to test whether differences between the sites are due to any particular factor, because the site factors are not replicated (Eberhardt and Thomas, 1991;Pennock, 2004).…”

Towards optimum sampling for regional-scale N2O emission monitoring in Canada

“…The key principle underlying the definition of the area and duration of the study is that the spatial extent (or area) of the study and the temporal extent (or duration) of the sampling program must match the scale of the process under study (Pennock 2004) -in this case agriculturally related N 2 O emissions.…”

“…Clearly the selection of sample numbers should be made on the basis of sound statistical analysis appropriate for the design selected for the study. Manipulative designs (which involve imposed treatment levels) will typically have lower variation among treatments than the comparative mensurative (Pennock 2004) designs that are used for the type of regional sampling program discussed in this study. Hence a smaller sample size may be appropriate for manipulative designs than for sampling of strata in regional-scale studies.…”

“…The spatial and temporal extent of the study must match the scale of the process under study (Pennock 2004), but our knowledge of the main N 2 O emitting processes continues to expand. For example, recent work by Wrage et al (2001) and Müller et al (2002Müller et al ( , 2004 has highlighted emission processes that are not as strongly controlled by soil water status as, for example, denitrification-related emissions.…”