Evaluation of potassium thiosulfate as a nitrification inhibitor to reduce nitrous oxide emissions

Potassium thiosulfate (KTS, K₂S₂O₃) has been shown to function as a nitrification inhibitor, thus has the potential to reduce nitrous oxide (N₂O) emissions and play an important role in effective N management. The objective of this research was to determine the potential effects of KTS on N₂O emissions and N transformation processes in comparison with commercial N transformation inhibitors (stabilizers). A laboratory incubation experiment was conducted using urea and ammonium nitrate (UAN) applied at 150mgNkg^-1 in a Hanford sandy loam soil (coarse-loamy, mixed, superactive, nonacid, thermic Typic Xerorthents). Treatments included three rates of KTS (26, 51, and 102mgS₂O₃^2--Skg^-1), a urease and nitrification inhibitor (Agrotain® Plus), a nitrification inhibitor (N-Serve® 24), and an untreated control. Nitrous oxide emission, soil pH, and mineral N species were monitored for 35days. Total N₂O emissions were reduced significantly by all KTS treatments as a function of KTS rate. At 102mgS₂O₃^2--Skg^-1, KTS reduced N₂O emissions by 48% (0.18% of total inorganic N), which was statistically similar to the N-Serve® 24 treatment (60% reduction) although lower than Agrotain® Plus (78% reduction). The KTS resulted in significantly less unaccounted (total N) loss compared to the commercial inhibitors. If the N₂O emissions reductions observed in this laboratory study are validated in the field, using KTS for this purpose can also provide a fertility benefit and may reduce total chemical inputs into agronomic systems. Future research needs to determine the effectiveness of thiosulfate for improving overall nutrient management while reducing N₂O emissions under field conditions.