Valorization of Sheep Wool: Impact of Keratin Hydrolysate on the Growth and Mineral Nutrition of Lettuce, Spinach, and Radish Plants

Abstract Sheep wool (SW) serves as a slow-release organic fertilizer, and its effectiveness can be enhanced through alkaline hydrolysis to break down keratin. The resulting keratin hydrolysate can support plant growth and improve mineral nutrition. Keratin hydrolysate obtained from sheep wool via the alkaline hydrolysis method was applied to lettuce, spinach, and radish plants at levels of 0, 0.5, 1.0, 1.5, 2.0, and 3.0 mL kg − 1 . Before starting the experiment, the molecular and chemical structure of sheep wool hydrolysate (SWH) was determined using Scanning Electron Microscopy, Fourier Transform Infrared Spectroscopy and Raman Spectroscopy. At the end of the study, the effects of SWH on plant growth and mineral nutrition were determined. Based on the experimental results, several amino acids, including alanine, glycine, tryptophan, valine, and methionine, were identified in the composition of the hydrolysate. Treatments with SWH significantly enhanced the growth of lettuce, spinach, and radish plants. Furthermore, these treatments led to a notable increase in the total nitrogen (N) concentration in the plants. Specifically, the calcium (Ca), magnesium (Mg), and iron (Fe) concentrations significantly increased in both lettuce and spinach. Additionally, SWH treatments elevated the zinc (Zn) concentration in radish tubers and the manganese concentration in lettuce plants. The copper (Cu) concentration in the plants also rose significantly following SWH treatments. The use of keratin hydrolysate derived from SW through the alkaline hydrolysis method demonstrates its potential to promote plant growth, emphasizing its significance in waste recovery and its transformation into a valuable resource.