How Do Newly-Amended Biochar Particles Affect Erodibility and Soil Water Movement?—A Small-Scale Experimental Approach

Steffen Seitz,Sandra Teuber,Thomas Scholten,Philipp Goebes,Christian Geißler

doi:10.3390/soilsystems4040060

Abstract

Biochar amendment changes chemical and physical properties of soils and influences soil biota. It is, thus, assumed that it can also affect soil erosion and erosion-related processes. In this study, we investigated how biochar particles instantly change erodibility by rain splash and the initial movement of soil water in a small-scale experiment. Hydrothermal carbonization (HTC)-char and Pyrochar were admixed to two soil substrates. Soil erodibility was determined with Tübingen splash cups under simulated rainfall, soil hydraulic conductivity was calculated from texture and bulk soil density, and soil water retention was measured using the negative and the excess pressure methods. Results showed that the addition of biochar significantly reduced initial soil erosion in coarse sand and silt loam immediately after biochar application. Furthermore, biochar particles were not preferentially removed from the substrate surface, but increasing biochar particle sizes partly showed decreasing erodibility of substrates. Moreover, biochar amendment led to improved hydraulic conductivity and soil water retention, regarding soil erosion control. In conclusion, this study provided evidence that biochar amendments reduce soil degradation by water erosion. Furthermore, this effect is detectable in a very early stage, and without long-term incorporation of biochar into soils.

Highlights

Biochar is charcoal obtained by thermal decomposition of biomass through pyrolysis [1,2].Similar to black carbon derived from the incomplete combustion of vegetation during wild fires, the carbon-enriched solid matter is known to improve, for example, cation exchange capacity or base saturation, as soils of the Amazon Basin indicate (“Terra Preta do Indio”; [3,4])
Biochar amendment led to improved hydraulic conductivity and soil water retention, regarding soil erosion control
Biochar had a significant effect on substrate losses in both silt loam and coarse sand treatments, but the effect was stronger with silt loam (Table 2)

Summary

Introduction

Biochar is charcoal obtained by thermal decomposition of biomass through pyrolysis [1,2].Similar to black carbon derived from the incomplete combustion of vegetation during wild fires, the carbon-enriched solid matter is known to improve, for example, cation exchange capacity or base saturation, as soils of the Amazon Basin indicate (“Terra Preta do Indio”; [3,4]). Biochar was introduced to other environments as a soil amendment. Its addition to topsoils can lead to significant changes in soil characteristics [1]. Its persistence in topsoils lasts longer than any other form of organic matter that is commonly used in agriculture. The effect of biochar generally relies on specific influences on the equilibrium between release (e.g., desorption) and fixation (e.g., adsorption) mechanisms in substrates [1,9]. Physical effects between soil and biochar are reported (e.g., [13,14]), which can affect soil texture and, erodibility of substrates, and the transport and storage of water within them [15,16,17,18,19,20]

Methods

Results

Conclusion