Impact of lignocellulosic and hemicellulosic biochar on soil moisture in low clay soils

Abstract

Investigation of post‐amendment biochar impact on low clay soil moisture provides agriculture professionals with much needed data. While laboratory testing is available, we propose inexpensive containers, tools and measuring devices to enable agriculture professionals to directly assess biochar impact on gravimetric water content, shrinkage, and release at point of soil rupture. Sandy loam, silty loam and loamy sand soils are amended (10% ) with lignocellulosic (oak) and hemicellulosic (cardboard) biochars in cup, plug and roll experiments. Cups with oak and cardboard biochar addition produced 76.32% and 75.72% H2O retention respectively, compared to 67.75% (67.75 g H2O 100 g−1 H2O) for controls. Cardboard and oak biochar limited diametric shrinkage to 2.95% (1.29 mm) and 3.75% (1.65 mm) respectively; controls shrunk 6.96% (3.06 mm). Oak and cardboard biochar limited depth shrinkage to 2.95% (0.38 mm) and 2.99% (0.38 mm) respectively; control depth shrinkage is 3.64% (0.47 mm). In roll tests, cardboard and oak biochar treatment yielded 28.07% (1.37 g H2O), and 26.69% (1.3 g H2O) moisture at rupture, respectively, compared with 11.98% (0.58 g) for controls. Significant (p ≤ 0.001) differences in moisture retention, shrinkage and available moisture at rupture confirm biochar contributions to improved moisture performance. Physico‐chemical analyses complemented experimental findings. We find study methods suit the needs of agricultural professionals to measure moisture while working with biochar to amend soils.

Pyrogenic Carbon Increases Pitch Pine Seedling Growth, Soil Moisture Retention, and Photosynthetic Intrinsic Water Use Efficiency in the Field

“…Retort PyC (Mitchell et al, 2016;Licht et al, 2017) was produced in an Adam-style retort (Sullivan Farm, Sullivan, New Hampshire USA). To gauge production temperature, a built-in retort probe and data logger continuously recorded temperature ever 6 h (reported in Licht et al, 2017) achieving T max in the 590-615 • C range. The T max results were consistent with experiments described by others (Mitchell et al, 2013;Ghorbel et al, 2015).…”

“…Identical volume samples (175 mL) were extracted and dried at 100 • C for 2 days, then placed in a 300 mL plastic cup to which 70 mL of H 2 O was added. These were measured for gravimetric moisture retention on a wet basis utilizing the Shields method to conduct these experiments as in Licht et al (2017). Net moisture retention as a subset of soil moisture evaporation (ψ g ) was determined over a 10 week period as net evaporative loss or adsorption to surfaces (Qi et al, 2018).…”

“…Repeated analyses of 240 mL volume samples were performed to determine inorganic and organic chemistry of pyrolysis charcoals. Tests were conducted using Modified Morgan digestive analysis following the procedure of Licht et al (2017). Due to low sample size, these data were not analyzed using the statistical methods indicated below, but results indicate that soil Ca, P, Mg, K, and Zn all tended to increase following PyC amendments (Table 4).…”

“…However, we suspect long-term moisture holding capacity over the length of the study increases as carbonates from anthropogenic PyC mineralize, resulting in increased total P sorption (Chintala et al, 2014) and C coalescence into pools (Preston and Schmidt, 2006). Researchers find forest soils react quickly to PyC dispersal based on substantial soil surface area (Sigmund et al, 2017)-exponentially greater than bare soilwhich accommodates greater nutrient uptake and improves soil moisture retention (Licht et al, 2017). Where wildfire is no longer experienced, such as in coastal sand plain pitch pine forests (Lee et al, 2018), and prescribed fire is employed, there is a need to determine if alternative sources may be found to replicate positive impacts of prescribed fire PyC.…”

“…PyC efficacy is measured in terms of soil moisture sorption and retention (Licht et al, 2017), which influence growth potential. Forest PyC has been found to temporarily disrupt water holding capacity in O a -A b horizon soil pores as a function of short-term hydrophobicity (Mikita-Barbato et al, 2015).…”