(180ax) Cellulose Nanofiber/Dolomite Clusters for Improving Soil Structure and Function

Understanding the structural and physicochemical changes that occur in soil during acidification and liming remains limited, largely because of the soil’s uniquely complex natural system, shaped by spatial heterogeneity, particle–pore arrangements, order–disorder patterns, and microstructural dynamics. To address this, we explore the potential of clay/cellulose nanofiber-based composite clusters as multifunctional soil modifiers. SEM micrographs revealed that biomass-derived cellulose fibers and finely ground dolomite (70:30 wt% ratio) formed a cellulose nanofiber/dolomite cluster (CNFDol) composite with a uniform distribution of fibers and clay particles, indicating effective integration. The UV/Vis spectra further confirmed coordination and hydrogen-bonding interactions among the components. These interactions could promote uniform spreading of clay particles within the cellulose matrix and suppress agglomeration, resulting in a more homogeneous and compact composite.

We found that CNFDol-treated model soil exhibited a wide particle size distribution while maintaining a uniform arrangement of components, creating a complex yet ordered–disordered system. The model soil, composed of sand (70%), kaolin (20%), and montmorillonite (10%), was systematically designed to approximate natural Ultisols—highly degraded soils characterized by strong acidity, intense weathering, and nutrient depletion—thus providing a complex but reproducible soil system. Within this structure, finer clay particles and cellulose fibers promoted aggregate formation, while coarser sand particles contributed to the structural framework. This effect was confirmed by a fourfold increase in mean weight diameter (MWD) of CNFDol-treated soil (9.7 mm) compared to untreated model soil (2.5 mm), as measured by wet sieving method. By contrast, soils treated with cellulose alone and dolomite alone showed smaller MWD values of 6.1 mm and 4.2 mm, respectively.

Similarly, CNFDol treatment significantly enhanced water absorption and retention. CNFDol-amended soils exhibited a 2.5-fold increase in water-holding capacity compared to untreated soils, surpassing both cellulose- and dolomite-only treatments. Over a three-week experiment, CNFDol-treated soils retained three times more water than untreated soils by day 7 and maintained 41% moisture after two weeks, whereas untreated soils had completely dried. Remarkably, CNFDol soils continued to retain water for over 20 days. We attribute this property to the enhanced porosity of CNFDol-treated soils, which allows greater water storage while reducing evaporation during drying. In addition, the high charge density of clay/cellulose clusters likely strengthens hydrogen-bonding interactions with water, contributing to the superior retention relative to pristine dolomite or cellulose.

Furthermore, pH measurements over 30 days showed that CNFDol gradually adjusted soil pH to an ideal range of 6.0–6.5, suitable for most crops. In contrast, calcite- and dolomite-treated soils exhibited a rapid rise to ~8 within a few days, creating undesirable alkalinity. We attribute the moderated pH adjustment in CNFDol soils to two factors: (i) negatively charged hydroxyl groups on cellulose acting as buffering agents, and (ii) slow release of Ca and Mg ions from DOPAC clusters, where binding to cellulose hydroxyl groups delays their availability. This slow-release mechanism not only prevents sudden alkalization and modifier loss through runoff, but also supports a more controlled nutrient cycling. In conclusion, the developed novel CNFDol complex composite showed promise as a low cost alternative to regenerate structure and properties of degraded soil by correcting pH, enhancing aggregate stability, and water retention capacity. Additional experimental data will be presented in detail at the conference.

Keywords: Cellulose nanofiber, Microstructure, Moisture retention, Soil acidity

References

Situ G., et al. 2022. Sci. Total Environ, 847, 157460

Gentile R., et al. 2011. Plant and Soil, 338, 1