Nitrogen

Water scarcity is an increasingly critical global issue, particularly in arid regions like Morocco. Innovative approaches, such as the use of alternative water sources like landfill leachate, offer promising solutions. In this study, phosphate washing sludge was used to treat landfill leachate with the aim of producing irrigation-quality water and recovering nitrogen from the resulting sediment. A total of 40 L of raw leachate was treated with three concentrations of phosphate washing sludge (25%, 37%, and 50%). This volume was processed at the laboratory scale as a proof of concept for potential larger-scale applications. After 24 to 36 h of mixing and agitation, the mixture underwent sedimentation, yielding clear supernatants and nitrogen-rich sludge pellets. These pellets showed a significant increase in organic matter content, from 6.4% to 13.5%, representing an enhancement of 110.9%, thus demonstrating partial leachate depollution and organic matter enrichment. Microbiological analyses revealed a 98.9% reduction in fecal streptococci. The supernatants met irrigation water standards in terms of pH and electrical conductivity, and phytotoxicity tests on maize seeds confirmed their suitability for irrigation. Additionally, the recovered nitrogen-rich sediment presents a valuable input for composting and soil amendment.

Nitrogen (N) is the most widely used nutrient in agriculture in the form of urea, yet it is one of the least efficient in terms of application due to losses through volatilization and leaching. The combination of urea with micronutrient sources, especially in the form of nanoparticles, is a promising technology for reducing these losses. Two greenhouse experiments were conducted with the objective of evaluating the influence of coating urea with zinc oxide nanoparticles (NPZnO) and iron oxide nanoparticles (NPFe₂O₃), associated with elemental sulfur (S°), on the leaching of mineral nitrogen and the production of dry mass and accumulation of N in young corn plants. The coating (0.26% w/w) of urea with elemental sulfur (S°) and NPZnO and NPFe₂O₃ reduced N losses through leaching (−21.3%) and delayed the nitrification process of N in the soil (−71.8%). This coating increased the efficiency of nitrogen fertilization in young corn plants, boosting the production of dry mass in leaves (+39.4%), stems (+68.8%), and roots (+61.6%), as well as the absorption of N in the above-ground biomass (+64.1%), compared to conventional urea. The use of urea coated with NPZnO and NPFe₂O₃ associated with S° is an environmentally sound solution for supplying N and micronutrients such as Fe and Zn in a more efficient and sustainable manner, especially in sandy soils with low organic matter content, which are common in the semi-arid region of Brazil.

The extensive use of synthetic nitrogen fertilizers has sustained global food production for more than a century but at high environmental and energetic costs. Improving nitrogen use efficiency (NUE) has therefore become a key objective to maintain productivity while reducing the ecological footprint of agriculture. This review synthesizes current knowledge on the biological foundations of NUE enhancement, focusing on the role of microbial biofertilizers and biostimulants. The main mechanisms through which plant-associated microorganisms contribute to nitrogen acquisition and assimilation are analyzed. In parallel, advances in genomics, biotechnology, and formulation science are highlighted as major drivers for the development of next-generation microbial consortia and bio-based products. Particular attention is given to the current landscape of commercial biofertilizers and biostimulants, summarizing the principal nitrogen-fixing and plant growth-promoting products available on the market and their agronomic performance. Moreover, major implementation challenges are discussed, including formulation stability and variability in field results. Overall, this review provides an integrated perspective on how biological innovations, market evolution, and agronomic optimization can jointly contribute to more sustainable nitrogen management and reduce dependence on synthetic fertilizers in modern agriculture.