The effect of nitrification inhibitors on the nitrous oxide (N₂O) release from agricultural soils—a review

Abstract

The use of nitrification inhibitors (NI) is a technique which is able to improve N fertilizer use efficiency, to reduce nitrate leaching and to decrease the emission of the climate-relevant gas N 2 O simultaneously, particularly in moderately fertilized agricultural systems adapted to plant N demand. The ammonia monooxygenase (AMO) is the first enzyme which is involved in the oxidation of NH þ 4 to NO À 3 in soils. The inhibition of the AMO by NIs directly decreases the nitrification rate and it reduces the NO À 3 concentration which serves as substrate for denitrification. Hence, the two main pathways of N 2 O production in soils are blocked or their source strength is at least decreased. Although it has been shown that archaea are also able to oxidize NH 3 , results from literature suggest that the enzymatic activity of NH 3 oxidizing bacteria is the most important target for NIs because it was much stronger affected. The application of NIs to reduce N 2 O emissions is most effective under conditions in which the NI remains close to the N-fertilizer. This is the case when the NI was sprayed on mineral-N fertilizer granules or thoroughly mixed with liquid fertilizers. Most serious problems of spatial separation of NI and substrate emerge on pasture soils, where N 2 O hotspots occur under urine and to a lesser extent under manure patches. From the few studies on the effect of different NI quantities it seems that the amount of NI necessary to reduce N 2 O emissions is below the recommendations for NI amounts in practice. NIs can improve the fertilizer value of liquid manure. For instance, the addition of NIs to slurry can increase N uptake and yield of crops when NO À 3 -N leaching losses are reduced. It has clearly been demonstrated that NIs added to cattle slurry are very effective in reducing N 2 O as well as NO emissions after surface application and injection of slurry into grassland soils. In flooded rice systems NIs can reduce CH 4 emission significantly, whereas the effect on CO 2 emission is varying. On the other hand, as an effect of the delay of nitrification by NIs, NH 3 emission might increase when N fertilizers are not incorporated into the soil. As compared to other measures NIs have a high potential to reduce N 2 O emissions from agricultural soils. Further, no other measure has so consistently been proofed according its efficiency to reduce N 2 O emissions. From the published data [Akiyama et al. (2010) and more recent data from the years 2010-2013; 140 data sets in total] a reduction potential of approx. 35% seems realistic; however, further measurements in different management systems, particularly in regions with intense frost/thaw cycles seem necessary to confirm this reduction potential. These measurements generally should cover a whole annual cycle.

Residual effect of BNI by Brachiaria humidicola pasture on nitrogen recovery and grain yield of subsequent maize

“…Strategies to suppress nitrification after N fertilization could result in higher uptake of N in the form of NH 4 + by crops and might be additionally beneficial for plants preferring + (Boudsocq et al 2012), while reducing N losses to the environment. Synthetic nitrification inhibitors (SNIs) like nitrapyrin, 3,4-dimethylpyrazole phosphate (DMPP) and dicyandiamide (DCD) were shown to inhibit the activity of soil nitrifiers, but persistence of their effectiveness depends strongly on environmental factors (Zerulla et al 2001;Fillery 2007;Ruser and Schulz 2015). In addition, prices for SNIs are beyond the reach of smallholders that manage low input systems in tropical and subtropical regions.…”

The mobility of nitrification inhibitors under simulated ruminant urine deposition and rainfall: a comparison between DCD and DMPP

“…Differences in efficacy have been attributed to a lower mobility of DMPP in comparison to DCD, due to a greater sorption of DMPP Zerulla et al 2001;Di and Cameron 2012). Having a high mobility may lead to the spatial separation of NI from NH 4 + and nitrifying microorganisms (Ruser and Schulz 2015).…”

Manure and sorbent fertilisers increase on-going nutrient availability relative to conventional fertilisers

“…Nitrogen transformation inhibitors (urease and nitrification inhibitors) may be less expensive than encapsulated fertiliser products, however, they tend to be temperature sensitive (breaking down as temperatures increase; Irigoyen et al, 2003;Ruser and Schulz, 2015), and there are health concerns regarding the application of some forms of inhibitors (hydroquinone; Trenkel, 2010). Even where there is no demonstrated health effect, observation of residues in agricultural products (e.g.…”