Effect of the nitrification inhibitor 3,4-dimethylpyrazole phosphate (DMPP) on N-turnover, the N2O reductase-gene nosZ and N2O:N2 partitioning from agricultural soils

Abstract

Nitrification inhibitors (NIs) have been shown to reduce emissions of the greenhouse gas nitrous oxide (n 2 O) from agricultural soils. However, their N 2 O reduction efficacy varies widely across different agroecosystems, and underlying mechanisms remain poorly understood. To investigate effects of the NI 3,4-dimethylpyrazole-phosphate (DMPP) on N-turnover from a pasture and a horticultural soil, we combined the quantification of N 2 and N 2 O emissions with 15 N tracing analysis and the quantification of the N 2 O-reductase gene (nosZ) in a soil microcosm study. Nitrogen fertilization suppressed nosZ abundance in both soils, showing that high nitrate availability and the preferential reduction of nitrate over N 2 O is responsible for large pulses of N 2 O after the fertilization of agricultural soils. DMPP attenuated this effect only in the horticultural soil, reducing nitrification while increasing nosZ abundance. DMPP reduced N 2 O emissions from the horticultural soil by >50% but did not affect overall n 2 + N 2 O losses, demonstrating the shift in the N 2 o:n 2 ratio towards N 2 as a key mechanism of N 2 O mitigation by NIs. Under non-limiting NO 3 − availability, the efficacy of NIs to mitigate N 2 O emissions therefore depends on their ability to reduce the suppression of the N 2 O reductase by high NO 3 − concentrations in the soil, enabling complete denitrification to N 2 .Agricultural soils have become the main source of anthropogenic nitrous oxide (N 2 O), a powerful greenhouse gas and the single most important substance depleting stratospheric ozone 1 . Delaying the conversion of ammonium (NH 4 + ) to nitrate (NO 3 − ), nitrification inhibitors (NIs) have been suggested as a means to reduce N 2 O emissions from agricultural soils. NIs demonstrated their efficacy across different cropping soils 2 , but results vary widely, and in particular in pasture soils the use of NIs had no or little effect on N 2 O emissions 3-5 . Despite a growing body of research on NIs, mechanisms and factors determining their efficacy to reduce N 2 O emission remain poorly understood 6 . The challenges to understand these mechanisms derive from the fact that N 2 O is formed via several different pathways in the soil matrix 7 , tightly coupled to different processes of N supply and consumption 8 . Critically, N 2 O can be further reduced to N 2 via the microbial-mediated process of denitrification, and the sole quantification of N 2 O as affected by NIs provides therefore only a limited insight into mechanisms of N 2 O mitigation using NIs.Microbial metabolic pathways can contribute via a wealth of different processes to N 2 O production and consumption, i.e. the reduction to N 2 in soils. Apart from abiotic processes, N 2 O formation can be categorized into www.nature.com/scientificreports www.nature.com/scientificreports/ nitrification-mediated pathways, denitrification and biotic formation of hybrid N 2 O 9 . Denitrification is generally assumed to be the main process contributing to overall N 2 O production from agricultu...

The model structure of the copper-dependent ammonia monooxygenase

“…However, their mode of action is not known at the molecular level, and they are thought to act as chelators of the essential copper atom present in the active site of AMO, an unproven hypothesis, while other more potent inhibitors are known but not marketed for field applications [ 5 ]. Moreover, their efficacy to reduce nitrogen losses has been shown to be highly variable and depending on many environmental conditions [ 29 , 30 ]. In any case, it is important to consider the environmental toxicity, the solubility as well as the concentrations required to modulate nitrification [ 31 , 32 ].…”

Gross Ammonification and Nitrification Rates in Soil Amended with Natural and NH4-Enriched Chabazite Zeolite and Nitrification Inhibitor DMPP

“…The same fertilization rate was also used in previous field experiments of the ZeoLIFE project [28] and in laboratory studies involving the same soil and zeolites [22]. As an additional factor, in a separate batch, each treatment received 2.916 µ g −1 of the nitrification inhibitor DMPP in liquid form, corresponding to 0.6% of the fertilizer added, according to [35,38]. This dosage also reflects the amount of DMPP that is commonly contained in granulated formulations [51,54].The tested treatments thus resulted in the following six combinations in four replicates:…”

“…Depending on the environmental conditions, substantial amounts of the potent greenhouse gas N 2 O are emitted from soil, unless the whole N 2 O is converted to N 2 by the enzyme N 2 O reductase encoded by nosZ. The abundance of the functional gene amoA and the genes nirS and nosZ can give indications on the efficiency of the respective processes [38][39][40][41].…”

“…Immediately after the incubation procedure (24 h), soil samples were homogenized and subsamples of 0.25 g soil were taken to extract total DNA in 3 replicates. DNA was extracted using the PowerSoil ® DNA Isolation Kit from MoBio (Mobio Laboratories, Inc., Carlsbad, CA, USA) according to the manufacturer's instructions, with the following modification: the soil was extracted twice by using the same soil and PowerBead Tubes to increase the recovery of DNA [38]. DNA concentration and quality were determined spectrophotometrically (NanoDrop 2000, Thermofisher, MA, USA).…”

Biochar and DMPP Regulated Root-Zone CO2, N2O and CH4 Emissions of Soil-Ridged/Substrate-Embedded Cultivation Sweet Pepper in Chinese Solar Greenhouse

“…It has been reported that DMPP has several obvious advantages over other currently used NIs. This compound is highly effective at inhibiting soil nitrification, reducing N2O emissions, increasing N fertilizer efficiency and crop yields [25,26] . Previous studies have shown that the application of DMPP in intensive vegetable fields significantly reduced the cumulative soil N2O emissions by 75% [27][28][29][30] .…”