Utilizing Agricultural, Animal, and Fisheries Wastes as Sustainable Phosphorus and Potassium Sources for Crop Production in a Circular Economy

Phosphorus (P) and potassium (K) are critical nutrients for crop production, forming the backbone of food security and soil health. However, growing global demand for these nutrients is depleting finite phosphate and potash reserves, raising significant sustainability concerns. Inefficient P use in agriculture further exacerbates the problem. Compounding the challenge, many countries rely heavily on imports to meet their potash fertilizer needs, creating economic and geopolitical vulnerabilities. Transitioning from finite mineral reserves to sustainable alternatives is imperative. Agricultural, animal, and fisheries wastes—such as crop residues, manure, fish processing by-products, and other organic materials—offer underutilized yet abundant sources of P and K. Recycling these wastes into fertilizers reduces dependency on mined resources and minimizes environmental impacts. This approach aligns with the circular economy model, fostering resource efficiency, supporting farmers, and ensuring long-term.

The low use efficiency of P fertilizers (15–20%) leads to the majority (80–85%) of applied P becoming fixed in the soil. This results in substantial reserves of fixed P in soils where P fertilizers are regularly applied. Unlocking this reserve P through chemical (e.g., ligands like anions of low molecular weight organic acids, carbonate, silicate, etc.), biological (phosphate solubilizing microbes), biochar-based amendments, or bio-chemical approaches (combination of chemical agents, biochar, and microbes) can significantly reduce the need for additional P fertilizers. On the other hand, inadequate or no K inputs under intensive agriculture can irreversibly alter important soil minerals and deteriorate soil health, which is a common problem in several K-fertilizer importing countries. P and K-rich wastes from agro-industries, animal husbandry, and fisheries present an untapped resource that can be processed into effective fertilizers using composting, biochar preparation, or other innovative fertilizer preparation technologies, ultimately reducing dependence on conventional sources. This Research Topic aims to compile evidence on the potential of such waste materials and explore innovative, cost-effective technologies for converting them into sustainable P or K fertilizers. By addressing these challenges, we can enhance resource efficiency and promote sustainable agricultural practices.

Original research, review, and mini-review papers on utilization of P- or K-rich wastes from agro-industries (e.g., crop residues, sugarcane press mud, oilseed cakes, grain-processing by-products, food-processing industry wastes, brewery wastes, fruit and vegetable peels, etc.), livestock (animal urine, animal dung, bone meal, blood meal, carcasses, slaughterhouse wastes, poultry/dairy/piggery manures, etc.), and fisheries (e.g., fish processing waste, aquaculture sludge, seafood waste/by-products, waste water, etc.) through innovative and cost-efficient technologies, and utilization of fixed P and K in soils through inorganic or organic ligands or P- and K-solubilizing microbes, are within the scope of this Research Topic.

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This Research Topic accepts the following article types, unless otherwise specified in the Research Topic description:

• Brief Research Report
• Data Report
• Editorial
• FAIR² Data
• General Commentary
• Hypothesis and Theory
• Methods
• Mini Review
• Opinion
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Article types

This Research Topic accepts the following article types, unless otherwise specified in the Research Topic description:

• Brief Research Report
• Data Report
• Editorial
• FAIR² Data
• General Commentary
• Hypothesis and Theory
• Methods
• Mini Review
• Opinion
• Original Research
• Perspective
• Policy and Practice Reviews
• Policy Brief
• Review
• Systematic Review

Keywords: Agro-industrial by-products, Animal byproducts, Bone-meal fertilizers, Biochar, Fishery wastes, Fixed phosphorus, Ligand exchange, Nutrient recovery, Nutrient recycling, Potassium input

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