Upcycling Discarded Pig Bedding into Compost Pellets for Green Agriculture: Nutrient Release Kinetics and Plant Growth

Purpose

This study investigated the effect of biochar amended-discarded pig bedding upcycled into compost pellets, and use of bio-fermented liquid for chitosan coating of these pellets on nutrient release behavior, soil microbial communities, and plant growth.

Methods: Dried pig bedding (Pi) of 3–5 mm was mixed with coconut biochar (B) at 0–25% (w/w), pelletized using corn flour as a binder and labelled Pi, p, PiB1, PiB5, PiB10, PiB15, PiB20 and PiB25. All pellets were analyzed for organic carbon, organic matter and seed germination index. Nutrient release of nitrogen (N), phosphorus (P), and potassium (K) was evaluated by shaking 1 g of pellets in 100 mL deionized water and fitted to the Korsmeyer–Peppas model. Selected pellets (Pi, p and PiB20) were coated with chitosan mixed with bio-fermented liquid (Pi, p-CBF, coat and PiB20-CBF, coat), then applied on topsoil at the dosage of 3 and 5% for cultivation of Pakchoy (Brassica rapa chinensis) in a laboratory-scale greenhouse.

Results: Biochar amendment can promote the N, P, K contents and improve nutrient retention with PiB20 exhibited maximum nutrient content (0.95–1.13% N, 0.50–0.97% P and 0.95–1.28% K). Chitosan coated pellets could reduce the rate of nutrient release. The release mechanism of N and P was an erosion-controlled process, whereas K was by diffusion. Application of 5% Pi, p-CBF, coat on topsoil enhanced the biomass yield which was related to beneficial changes in soil microbial community. Conclusion: Overall, biochar amendment and chitosan coating improved compost pellet nutrient efficiency and promoted sustained nutrient release and plant growth.