The potential of recycling wool residues as an amendment for enhancing the physical and hydraulic properties of a sandy loam soil

Abstract

Purpose Climate change and global food demand in coming decades urge effective actions for more efficient uses of water and soil resources. This paper reports the preliminary findings of a study assessing the potential of sheep scoured wool residues (SWRs) as soil amendments to enhance the physical and hydraulic properties of a sandy loam soil under rain conditions. Methods Two different SWRs were used: scoured residues (white wool, WW) and carbonized scoured residues (black wool, BW) at different SWRs/soil ratios (0.0, 0.5, 1.0 and 2.0%). Soil bulk density (BD), total porosity (TP), aggregates stability, aggregate size distribution, saturated hydraulic conductivity, and water retention properties were determined under rain conditions, in addition to rainwater balance (storage, percolation and runoff). Results Both WW and BW, particularly at the high wool/soil ratio (2%), significantly reduced soil BD by 11.98% and 9.85%, respectively. Moreover, WW and BW increased TP by 16.45% and 13.57% and available water capacity by 6.5% and 18.1%, respectively. SWRs increased the formation of macro-aggregates and increased aggregate stability. The results of rainwater balance showed higher percolation percentages and less rainwater storage in the wool-treated soil. Conclusions The increase in water percolation is in line with the increased total porosity and the higher saturated hydraulic conductivity of wool-treated soil. Despite the high capacity of absorbing water, SWRs affected the water movement of the soil more than its water retention.

Assessment of Two Sheep Wool Residues from Textile Industry as Organic Fertilizer in Sunflower and Maize Cultivation

“…However, the prolonged direct contact to such materials, may have inferred on plant development because of soil acidity as found in the previous study (Abdallah et al 2019) or because of osmotic and ionic stresses (Flowers and Colmer 2008) due to an increase of salinity. Indeed, water evaporation during the experiment generated a visible abundant salt efflorescence on the soil surface ( Fig.…”

“…In the sunflower experiment, soil moisture was significantly increased only at the highest wool concentrations (WW2% and BW2% treatments), likely because of the higher water inhibition of wool fibers (Abdallah et al 2019;Mubarak et al 2009;Murray et al 2000;Zoccola et al 2015). Regarding the eco-physiological behavior, the higher moisture also favored plant hydration: leaf water potentials at pre-dawn and at midday were higher in SWRs at 2% but also in CTRL.…”

“…The lower soil moisture in low SWR concentrations (0.5 and 1%) also resulted in lower leaf water potentials (even at pre-dawn, when water balance between soil and plant is reached). In these treatments, lower moisture might be due to a higher water loss by percolation (Abdallah et al 2019), but could also result from high evaporation through the soil pores. Therefore, differences between minimum and predawn water potentials were relatively small, with the only exception being WW0.5%, which recorded the lowest absolute minimum water potential values.…”

“…Wool waste can have also beneficial effects on the soil (Abdallah et al 2019). Mubarak et al (2009) found a decrease in water movement in sandy soils amended with organic residues including sheep wool, while Murray et al (2000) found an increase of 1% moisture content for every 1% increase of carpet fiber in soil.…”

“…One SWR type was generated by the first step of the scouring process of wool, while the other type was the residue from the successive acid washing of the scoured wool, and it has never been investigated. This study, on the basis of encouraging results from former tests on SWRs applied as amendments in a sandy loam soil (Abdallah et al 2019), aims to assess the suitability of the two SWRs for the growth of two plant species with high (maize) and low (ornamental sunflower) nitrogen requirement.…”