3,4-dimethylpyrazole phosphate (DMPP) Reduces N2O Emissions from a Tilled Grassland in the Bogotá Savanna

Dimethylpyrazole-based nitrification inhibitors have a dual role in N2O emissions mitigation in forage systems under Atlantic climate conditions

Nitrogen fertilization is the most important factor increasing nitrous oxide (N₂O) emissions from agriculture, which is a powerful greenhouse gas. These emissions are mainly produced by the soil microbial processes of nitrification and denitrification, and the application of nitrification inhibitors (NIs) together with an ammonium-based fertilizer has been proved as an efficient way to decrease them. In this work the NIs dimethylpyrazole phosphate (DMPP) and dimethylpyrazole succinic acid (DMPSA) were evaluated in a temperate grassland under environmental changing field conditions in terms of their efficiency reducing N₂O emissions and their effect on the amount of nitrifying and denitrifying bacterial populations responsible of these emissions. The stimulation of nitrifying bacteria induced by the application of ammonium sulphate as fertilizer was efficiently avoided by the application of both DMPP and DMPSA whatever the soil water content. The denitrifying bacteria population capable of reducing N₂O up to N₂ was also enhanced by both NIs provided that sufficiently high soil water conditions and low nitrate content were occurring. Therefore, both NIs showed the capacity to promote the denitrification process up to N₂ as a mechanism to mitigate N₂O emissions. DMPSA proved to be a promising NI, since it showed a more significant effect than DMPP in decreasing N₂O emissions and increasing ryegrass yield.

Urea Ammonium Nitrate Solution Treated with Inhibitor Technology: Effects on Ammonia Emission Reduction, Wheat Yield, and Inorganic N in Soil

Urea is the most used fertilizer nitrogen (N), and is often applied as urea ammonium nitrate (UAN), which may be an ammonia (NH3) emission source after application. This study examined whether the addition of urease inhibitors reduced NH3 emission, and, in combination with nitrification inhibitors, enhanced fertilizer N crop uptake. In three experiments, NH3 emission was measured from plots (100 m2) to which UAN was added with and without inhibitors. In March and May, the plots were covered with Triticum aestivum L., Sheriff (var), and in July, the soil was bare. The inhibitor mixed with urea was N-(n-butyl) thiophosphoric triamide (NBPT) and a mixture of NBPT and the new nitrification inhibitor DMPSA (3,4-Dimethylpyrazole succinic acid). Ammonia emissions were negligible from all plots after the first application of UAN due to the wet and cold weather while an average of 7% of applied UAN was emitted after application of UAN in April, where no significant effect of additives was observed. The harvest yield was low due to drought from May till August. Yield was highest when UAN was mixed with NBPT and lowest for untreated UAN. The highest emission from the bare plots was obtained from untreated UAN (17% of N), in contrast to 11% of N from the plots with added UAN + NBPT (not significant) and 7% from the plots with added UAN + NBPT + DMPSA (significantly different). Under the conditions of the current study, urease inhibitors reduce NH3 emissions in periods where the risk of emission is high, and the combination of urease and nitrification inhibitors increased yields.

Effect of N dose, fertilisation duration and application of a nitrification inhibitor on GHG emissions from a peach orchard

Despite only occupying 5% of the worldwide arable area, fruit tree crops are of vital economic importance in many regions. Intensive cropping practices can lead to greenhouse gas (GHG) emissions. In order to reduce these emissions, numerous studies have been made on lowering N inputs or applying nitrification inhibitors (NIs) which tend to maintain or even increase yield while reducing N leaching and nitrogenous emissions to the atmosphere. However, very few studies have been conducted on potential GHG emissions from the peach crop. In this work, a three-year study was carried out in a commercial peach orchard with a split-plot design with three replicates, in which the main factor was N dose (25, 50 and 100 kg N ha^-1 year^-1, and 50 kg N ha^-1 year^-1 applied during a shorter period of time in 2015 and 2016; and only 70 kg N ha^-1 year^-1 in 2017). Subplots in the study were used to analyse the effect of the application of a NI (3,4-dimethylpyrazole phosphate; DMPP). The aim was to qualitatively compare the effect of these factors on N₂O, N₂O + N₂, CH₄ and CO₂ emissions from a peach orchard soil in order to recommend agricultural practices that minimise emissions without concurrent yield reductions. We show that N₂O and N₂O + N₂ emissions were linked to fertilisation and increased with N dose. The N₂O emissions were mitigated (up to 49%) by DMPP up to the 50 kg N ha^-1 dose (not significantly). It seems that between 70 and 100 kg N ha^-1 the application of DMPP loses effectiveness. Methane oxidation increased with N dose and decreased with DMPP application; CO₂ emissions increased with DMPP and were unaffected by N dose. The intermediate N dose (50 kg N ha^-1) applied during a shorter period of time increased yield (not significantly) and NUE without increasing GHG emissions.

The Nitrification Inhibitor Vizura® Reduces N2O Emissions When Added to Digestate before Injection under Irrigated Maize in the Po Valley (Northern Italy)

The agricultural area in the Po Valley is prone to high nitrous oxide (N2O) emissions as it is characterized by irrigated maize-based cropping systems, high amounts of nitrogen supplied, and elevated air temperature in summer. Here, two monitoring campaigns were carried out in maize fertilized with raw digestate in a randomized block design in 2016 and 2017 to test the effectiveness of the 3, 4 DMPP inhibitor Vizura® on reducing N2O-N emissions. Digestate was injected into 0.15 m soil depth at side-dressing (2016) and before sowing (2017). Non-steady state chambers were used to collect N2O-N air samples under zero N fertilization (N0), digestate (D), and digestate + Vizura® (V). Overall, emissions were significantly higher in the D treatment than in the V treatment in both 2016 and 2017. The emission factor (EF, %) of V was two and four times lower than the EF in D in 2016 and 2017, respectively. Peaks of NO3-N generally resulted in N2O-N emissions peaks, especially during rainfall or irrigation events. The water-filled pore space (WFPS, %) did not differ between treatments and was generally below 60%, suggesting that N2O-N emissions were mainly due to nitrification rather than denitrification.