Potato (Solanum tuberosum L.) production in irrigated coarse-textured soils requires intensive nitrogen (N) fertilization which may increase reactive N losses. Biological soil additives including N-fixing microbes (NFM) have been promoted as a means to increase crop N use efficiency, though few field studies have evaluated their effects, and none have examined the combined use of NFM with microbial inhibitors. A 2-year study (2018–19) in an irrigated loamy sand quantified the effects of the urease inhibitor NBPT, the nitrification inhibitor DMPSA, NFM, and the additive combinations DMPSA + NBPT and DMPSA + NFM on potato performance and growing season nitrous oxide (N₂O) emissions and nitrate (NO₃⁻) leaching. All treatments, except a zero-N control, received diammonium phosphate at 45 kg N ha⁻¹ and split applied urea at 280 kg N ha⁻¹. Compared with urea alone, DMPSA + NBPT reduced NO₃⁻ leaching and N₂O emissions by 25% and 62%, respectively, and increased crop N uptake by 19% in one year, although none of the additive treatments increased tuber yields. The DMPSA and DMPSA + NBPT treatments had greater soil ammonium concentration, and all DMPSA-containing treatments consistently reduced N₂O emissions, compared to urea-only. Use of NBPT by itself reduced NO₃⁻ leaching by 21% across growing seasons and N₂O emissions by 37% in 2018 relative to urea-only. In contrast to the inhibitors, NFM by itself increased N₂O by 23% in 2019; however, co-applying DMPSA with NFM reduced N₂O emissions by ≥ 50% compared to urea alone. These results demonstrate that DMPSA can mitigate N₂O emissions in potato production systems and that DMPSA + NBPT can reduce both N₂O and NO₃⁻ losses and increase the N supply for crop uptake. This is the first study to show that combining a nitrification inhibitor with NFM can result in decreased N₂O emissions in contrast to unintended increases in N₂O emissions that can occur when NFM is applied by itself.

Mangrove areas are among most threatened tropical ecosystems worldwide. Among polluting agents Cadmium is often found in high concentrations in mangrove sediments. Humic substances, complex biomolecules formed in soil and sediments during animal and plant residuals decomposition, have a known biostimulant activity and can be adopted to counteract various plant stresses. This study explores, in controlled conditions, the effect of humic substances on Avicennia germinans seedlings, with or without cadmium contamination. Humic compounds significantly changed plant root architecture, and, when coupled with cadmium, root anatomy and Cortex to Vascular Cylinder diameter ratio. These modifications led to lower Cd uptake by humic substances-treated plants. Humic substances amendment could be effective, depending on their concentrations, on improving plant health in mangrove areas, for forest recuperation and/or dredged sediments phytoremediation purposes.