Uncomposted wool and hair-wastes as soil amendments for high-value crops
The hypothesis of this work was that uncomposted sheep wool and human hair could be used as nutrient source for nonedible high-value plants. Pot and field experiments were conducted to assess uncomposted sheep wool-wastes and human hair-wastes as a nutrient source for high-value crops and to evaluate the effect of these waste materials on soil microbial community and mycorrhizae. In the pot experiments, addition of uncomposted wool- or hair-waste to soil increased yields from pot marigold (Calendula officinalis L.) and valerian (Valeriana officinalis L.). In the field experiment, wool-waste was added to purple foxglove (Digitalis purpurea L.) at rates of 0, 15.8, and 31.7 t ha–1. Wool additions to soil increased foxglove yields over the next two seasons by 1.7 to 3.5 times relative to the control. Overall, addition of wool- or hair-waste to soil increased NH4–N and NO3–N in soil, increased total N (and protein) concentration in plant tissue, and stimulated soil microbial biomass. Scanning electron microscopy (SEM) and energy dispersive x-ray (EDX) analyses indicated that some of wool and hair in soil from the pot and field experiments, after two seasons and several harvests, retained their original structure, a significant concentration of S, some N, and were not fully decomposed. High rates of wool addition to soil in field experiments resulted in shifts in the microbial community composition, while a low rate of wool-waste addition did not affect the microbial community relative to the unamended control. Our results suggest that the addition of uncomposted wool-waste or hair-waste of only 0.33% by weight to soil would support at least 2 to 3 harvests of crops, without the addition of other fertilizers. Uncomposted wool and hair-wastes can be used as a nutrient source for high-value crops.