Combining nitrification inhibitors with a reduced N rate maintains yield and reduces N2O emissions in sweet corn

Intensive vegetable production is characterised by high nitrogen (N) application rates and frequent irrigations, promoting elevated nitrous oxide (N2O) emissions, a powerful greenhouse gas indicative for the low N use efficiency (NUE) in these systems. The use of nitrification inhibitors (NI) has been promoted as an effective strategy to increase NUE and decrease N2O emissions in N-intensive agricultural systems. This study investigated the effect of two NIs, 3,4-dimethylpyrazole phosphate (DMPP) and 3-methylpyrazole 1,2,4-triazole (Piadin), on N2O emissions and 15N fertiliser recovery in a field experiment in sweet corn. The trial compared the conventional fertiliser N rate to a 20% reduced rate combined with either DMPP or Piadin. The use of NI-coated urea at a 20% reduced application rate decreased cumulative N2O emissions by 51% without yield penalty. More than 25% of applied N was lost from the conventional treatment, while a reduced N rate in combination with the use of a NI significantly decreased N fertiliser losses (by up to 98%). Across treatments, between 30 and 50% of applied N fertiliser remained in the soil, highlighting the need to account for residual N to optimise fertilisation in the following crop. The reduction of overall N losses without yield penalties suggests that the extra cost of using NIs can be compensated by reduced fertiliser application rates, making the use of NIs an economically viable management strategy for growers while minimising environmentally harmful N losses from vegetable growing systems.