Abstract

UV irradiation is known to enhance the activity of keratinases and catalase in microbes. This study aimed to evaluate the decomposing capabilities of wild and UV-irradiated Bacillus subtilis strains. Therefore, wild and UV-irradiated strains (0, 60, 150 and 240 min) were allowed to degrade poultry feathers for 0, 30 and 60 days. The biodegraded products were used as supplements (0 and 3 g/kg soil) for cotton. The best-performing biocompost was chosen based on the correlation between its physical and chemical properties. Selected biocompost (60 days matured by 150 min of UV-irradiated B. subtilis) was applied as a rooting medium to stressed cotton (control and 50 mg K2Cr2O7/kg soil). Chromium (Cr) stress negatively affected growth, fiber and oil quality in untreated and feather-supplemented plants. B. subtilis-degraded biocomposts improved germination rate, index and percentage; leaf numbers, branches, chlorophyll a/b ratio, carotenoids, soluble proteins, amino acids and ascorbic acids; fiber elasticity, fiber uniformity index (FUI) and boll weight; and reduced coefficient of variation (CVt), fiber micronaire, malondialdehyde (MDA) and H2O2. Biocompost prepared from UV-irradiated B. subtilis strain (150 min) was better in terms of carbon/ nitrogen (C/N) ratio of compost, shoot fresh weight, germination percentage, shoot length, dry weight, chlorophyll a/b ratio, carotenoids, boll weight, seed number and unsaturated fatty acids. In summary, to grow cotton in Cr-stressed areas, feathers degraded by B. subtilis can serve as a beneficial, eco-friendly biocompost. UV irradiation can additionally enhance the efficiency of B. subtilis.