Nitrogen supplying capability of wool pellets as an alternative fertilizer depending on soil biological activity

Pellets made from waste wool, typically sourced from sheep shearing residues generated by the textile or wool industry, have recently emerged as a promising alternative for plant nutrition. However, limited information is available on the impact of wool pellets (WP), applied at a dosage of 4 g per pot, on soil functioning, biological activity, plant physiology, and nutrient supply. A pot experiment was set up in a randomized block design with four replicates on sweet peppers (Capsicum annuum L.). The effect of WP on permanganate-oxidizable carbon, fluorescein diacetate, and β-glucosidase enzyme activities were investigated in two soils differing in their soil organic matter (SOM) contents (low and high) and compared to the control and a reference N fertilizer solution. The nitrate and total nitrogen content of plants, the photosynthetic pigments, gas exchange intensity, shoot and root biomass, pepper fruit, and photosynthetic rate per total N-uptake were also examined. WP treatments (4 g per pot) increased soil biological activity in both soil types (with 0.58% and 1.84% soil organic matter, respectively) and significantly improved plant physiological parameters and N-use efficiency compared to the control and reference N fertilizer addition. Although the total N content in wool pellets was higher than in the mineral reference N-solution, this reference treatment served as a baseline dose allowing comparison with the N-supply intensity of the WP. WP significantly increased shoot biomass in both soil types, with a more pronounced effect in the low SOM soil due to faster mineralization and higher air capacity. In contrast, higher fruit was achieved in the high SOM soil. WP treatment increased N-uptake to 2.18 and 2.34 mg/week in low and high SOM, respectively. The research findings highlight wool pellets as a powerful alternative to inorganic fertilizers, offering a sustainable nutrient supply. Moreover, utilizing wool a by-product often considered waste as an organic fertilizer contributes to solving both economic and environmental challenges associated with wool disposal.