Location: Soil, Water & Air Resources ResearchTitle: Hydraulic deep-core sampling impacts bulk density and carbon stock measurements
|DOLD, CHRISTIAN - Orise Fellow|
|Sauer, Thomas - Tom|
|WACHA, KENNETH - Orise Fellow|
Submitted to: Agricultural and Environmental Letters
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/13/2018
Publication Date: 4/12/2018
Publication URL: https://handle.nal.usda.gov/10113/6557424
Citation: Dold, C., Hatfield, J.L., Sauer, T.J., Cambardella, C.A., Wacha, K.M. 2018. Hydraulic deep-core sampling impacts bulk density and carbon stock measurements. Agricultural and Environmental Letters. 3:180007. Available: https://dl.sciencesocieties.org/publications/ael/pdfs/3/1/180007.
Interpretive Summary: Soil samples taken with hydraulic samplers are prone to be compacted or have gaps, which affects bulk density. Bulk density is an important value to calculate total carbon stock, and also is important to evaluate soil quality. We compared bulk density measurements (0–120 cm) from hydraulic samples with soil pit samples within a corn and soybean rotation field in Central Iowa. Although bulk density samples among both methods varied substantially, especially in the subsoil, the samples were statistically not different, and carbon estimation was not impacted. Correcting bulk density with measurements of the sampling hole depth statistically underestimated bulk density from hydraulic samples, and is not recommended. Calculating carbon in soils with another approach using soil dry weight instead of bulk density, showed good results for the topsoil, but underestimated subsoil carbon. This study did not account for different field conditions, which can equally impact bulk density. Further studies are needed to investigate the impact of hydraulic sampling induced errors. This work is a first step to understand the impact of frequently used hydraulic samplers in soil sampling. It helps researchers to understand the impact of sampling induced errors on bulk density and soil carbon estimation.
Technical Abstract: Hydraulic sampling can induce artificial compaction or gaps in soil cores, which affects bulk density (BD) and carbon (C) stock estimation. We compared BD (0–120 cm) from hydraulic samples (BDhs) with soil pit samples (BDpit) within a corn (Zea mays, L.) and soybean (Glycine max) rotation field in Central Iowa. Although BDhs varied substantially compared to BDpit with RMSE of 0.15 g cm-3 and with increasing soil depth, this difference was not significant and did not significantly impact C stock estimates. Correcting for sampling hole depth significantly underestimated BDhs, and is not recommended. Calculating C stocks on a mass-based approach, thus avoiding BD effects, showed good results for the topsoil, but underestimated subsoil C. This study did not account for different field conditions, which can equally impact BDhs. Further studies are needed to investigate the impact of hydraulic sampling induced errors.