Nitrogen-enriched liquid organic fertilizers (LOFs) production for sustainable agriculture: A review

Purpose: Although the popularity of liquid organic fertilizers (LOFs) has considerably increased recently, there have been concerns over their usage due to low nitrogen content. This study aims to discuss the current developments in nitrogen-enriched LOFs that address the above limitation, subsequently promoting sustainable agricultural practices. Method: A thorough review of existing literature on nitrogen-enriched LOFs based on their chemical attributes and methodologies to increase the nitrogen content. Results: The research highlights several promising methods for nitrogen enrichment, such as using high-nitrogen raw materials like cottonseed meal, bone meal, and blood meal, which also provide phosphorus and potassium benefits. Also, techniques like thermal hydrolysis, plasma activation, and inoculation of microorganisms can release and fix nitrogen in LOFs. Membrane technologies promise sustainably by recycling organic waste. Combining these materials and processes results in well-balanced nutrient profiles and improve the agricultural value of LOFs. However, formulating nitrogen-enriched LOFs requires considering critical factors like organic carbon content, pH values, raw material availability, cost implications, and overall sustainability. Optimizing these factors potentially lead to eco-friendly solutions for sustainable agriculture. Conclusion: Cost-effective nitrogen enrichment in LOFs can be achieved through diverse methods and raw materials. Future investigations should focus on discovering raw materials with high nitrogen content, devising innovative enrichment techniques, and rigorously evaluating the efficacy of fertilizers. Investments in research, development, distribution, storage, packaging, and value-addition processes are essential to bolster LOF production and enhance affordability and accessibility, thus fostering sustainable agricultural practices.