Researchers face a number of challenges in the construction of soil columns which can affect the outcome of their experiments. The use of intact soil cores closely mimics actual field conditions. However, the excavation of large intact soil cores is a time-consuming, labor-intensive process and may lead to soil compaction that would influence the solute transport behavior of the soil column. Repacked soil columns are used as an option to circumvent these challenges of intact soil cores. However, repacked soil columns also have their limitations and introduce other challenges. Here, we present a step by step procedure for the design of repacked soil columns to achieve a realistic bulk density, prevent preferential flow paths, and ensure hydraulic connectivity between soil layers. This protocol will be beneficial to Soil Scientists, Hydrologists and other Environmental Scientists utilizing repacked soil columns.
Soil columns play important roles in experimental set up for monitoring the fate and mobility of solutes such as contaminants and nutrients. They are also used in evaluating solute transport models. Soil columns are used widely in studies on the fate and transport of nutrients, pesticides, microbes, and heavy metals (Lewis and Sjöstrom, 2010).
Specifically, soil columns have been used in several studies including leaching of pharmaceuticals (Oppel et al., 2004), response of root growth to soil compaction levels (Tracy et al., 2012), dissolved organic carbon and nitrate fluxes (Eykelbosh et al., 2015), fate of organic micropollutants (Banzhaf and Hebig, 2016), and modelling of micropollutants to simulate riverbank filtration (Bertelkamp et al., 2016).
The experimental setup has a great influence on the outcome of soil column studies (Bromly et al., 2007). Therefore, it is very vital to design soil columns in such a way as to overcome associated challenges and minimize any potential source of bias (Weihermuller et al., 2007). The purpose of this protocol is to provide a step-by-step guidance in the construction and use of repacked soil columns to obtain reproducible experimental outcomes.
Materials and Reagents
PVC pipes (e.g., sewer pipes having a thickness of 4.1 mm)
Silicon sealant and gun
Coarse textured Sandpaper
35-micron nylon mesh
Measuring tape
Syringe (10 ml)
Measuring cylinder
Collection trays
Supporting trays
Rhizon MOM (from Rhizosphere.com, catalogue number 19.21.21F )
Buckets
Ryegrass (or the plant of your interest)
Soil
100 seeds of perennial ryegrass (Lolium perenne)
Water
Equipment
Hand drill with various size bits (e.g., 0.5 mm, 1 mm)
Saw
3.35 mm mesh size sieve (depending on the purpose of the experiment)
Ikoyi, I. O. and Schmalenberger, A. (2021). Design and Construction of Repacked Soil Columns for Measuring Solute Transport, Plant Growth and Soil Biota. Bio-protocol 11(2): e3884. DOI: 10.21769/BioProtoc.3884.