Use Of Nitrification Inhibitors Research Articles

Nitrification Inhibitors: A Perspective tool to Mitigate Greenhouse Gas Emission from Rice Soils

Rice fields are significant contributors of greenhouse gases mainly methane and nitrous oxide to the atmosphere. Increasing concentrations of these greenhouse gases play significant role in changing atmospheric chemistry such as mean air temperature, rainfall pattern, drought, and flood frequency. Mitigation of greenhouse gases for achieving sustainable agriculture without affecting economical production is one the biggest challenge of twenty first century at national and global scale. On the basis of published scientific studies, we hereby assess the use of nitrification inhibitors for greenhouse gas mitigation from rice soil. Biologically oxidation of ammonium to nitrate is termed as nitrification and materials which suppress this process are known as nitrification inhibitors. Soil amendment by addition of certain nitrification inhibitors such as neem oil coated urea, nimin-coated urea; dicyandiamide, encapsulated calcium carbide, and hydroquinone reduce cumulative methane and nitrous oxide emission from rice. Firstly, these inhibitors reduce nitrous oxide emissions both directly by nitrification (by reducing NH4+ to NO3-) as well as indirectly by de-nitrification (by reducing NO3- availability in soil). Secondly, methane emission from rice soil can be reduced by enhancing methane oxidation and suppressing methane production and further by reducing the aerenchymal transportation through rice plant. Application of some of the nitrification inhibitors such as calcium carbide and encapsulated calcium carbide reduce methane production by releasing acetylene gas which helps in reducing the population of methanogenic microbes in the soil. Application of nitrification inhibitors also helps to maintain soil redox potential at higher level subsequently reducing cumulative methane emission from soil. Plant derived organic nitrification inhibitors (neem oil, neem cake, karanja seed extract) are eco-friendly and possess substantial greenhouse gas mitigation potential from rice. In the current scenario of global warming and environmental pollution, application of organic plant derived nitrification inhibitors is much needed for sustainable agriculture.

Application of Nitrapyrin with Banded Urea, Urea Ammonium Nitrate, and Ammonia Delays Nitrification and Reduces Nitrogen Loss in Canadian Soils

Core Ideas Nitrapyrin has been tested in fallow field trials in cereal and oilseed growing regions of Canada. Nitrapyrin maintained N in the ammonium form through critical loss periods. Nitrapyrin preserved more mineral N in the soil relative to non‐stabilized fertilizer. Soil N loss is a significant impediment to maximizing yield and profitability for farmers in Canada. Maintaining N in the stable and plant‐available NH4+ form via use of nitrification inhibitors limits the potential for soil N losses from denitrification or leaching. Between 2013 and 2015, twenty‐one research trials were established across the major cereal and oilseed growing regions of Canada to evaluate the efficacy of two commercially available formulated nitrapyrin products, eNtrenchTM and N‐Serve, at stabilizing soil N in the NH4+ form and protecting against N loss. Urea, urea ammonium nitrate (UAN) or NH3 fertilizer treatments were banded in the fall or spring on fallow land, and the soil was sampled to a depth of 60 cm at multiple time intervals after application. Fall applications of nitrapyrin resulted in 21–63% more NH4N, and 10–19% more total mineral N, at spring sampling after soil thaw relative to non‐stabilized fertilizer. Spring applications of nitrapyrin resulted in larger pools of NH4–N for at least 8 weeks after treatment, and they increased total mineral N by up to 25%, compared with non‐stabilized treatments. Results suggest that eNtrench and N‐Serve are useful tools for growers looking to protect their N investment, optimize crop yield potential, and enhance flexibility of their N application timing.

Changes in the activity and abundance of the soil microbial community in response to the nitrification inhibitor 3,4-dimethylpyrazole phosphate (DMPP)

The application of organic and inorganic fertilizers to soil can result in increased gaseous emissions, such as NH3, N2O, CO2, and CH4, as well as nitrate leaching, contributing to climate warming and ground and surface water pollution, particularly in regions with hot climates, where high temperatures and high soil nitrification rates often occur. The use of nitrification inhibitors (NIs) has been shown to effectively decrease nitrogen (N) losses from the soil-plant system. Non-disruptive laboratory incubation experiments were conducted to assess the extent to which temperature (20 and 30 °C) and nutrient source (mineral and organic fertilizers) influence the rate of carbon (C)- and N-related microbial processes in soil in response to the NI 3,4-dimethylpyrazole phosphate (DMPP). Furthermore, short-term changes in the ability of microbes to degrade C substrates were evaluated in disruptive soil microcosms using microbial community-level physiological profiling and the abundance of the bacterial 16S rRNA gene as a measure of total bacterial population size. DMPP reduced net nitrification after 2 and 4 weeks of incubation at 30 and 20 °C by an average of 78.3 and 84.5 %, respectively, and with similar dynamics for mineral or organic fertilization. The addition of labile organic matter with cattle effluent led to a rapid increase in C mineralization that was significantly reduced by DMPP at both temperatures, whereas no changes could be detected after the addition of mineral fertilizer. The culturable heterotrophic microorganisms showed metabolic diversification in the oxidation of C sources, with organic fertilizer playing a major role in the substrate utilization patterns during the first week of incubation and the DMPP effects prevailing from day 14 until day 28. Furthermore, the copy number of the bacterial 16S rRNA gene was reduced by the application of DMPP and organic fertilizer after 28 days. Our results show the marked efficiency of DMPP as an NI at elevated temperatures of incubation and when associated with both mineral and organic fertilization, providing support for its use as a tool to mitigate N losses in Mediterranean ecosystems. However, we also observed impaired C respiration rates and bacterial abundances, as well as shifts in community-level physiological profiles in soil, possibly indicating a short-term effect of DMPP and organic fertilizers on non-target C-related processes and microorganisms.

Inhibition of nitrification to mitigate nitrate leaching and nitrous oxide emissions in grazed grassland: a review

Climate change is arguably the biggest environmental challenge facing humanity today. Livestock production systems are a major source of greenhouse gases that contribute to climate change. Nitrous oxide (N2O) is a potent greenhouse gas with a long-term global warming potential 298 times that of carbon dioxide (CO2). Nitrate (NO3 −) leaching from soil causes water contamination, and this is a major environmental issue worldwide. Agriculture is identified as the dominant source for NO3 − in surface and ground waters. In grazed grassland systems where animals graze outdoor pastures, most of the N2O and NO3 − are from nitrogen (N) returned to the soil in the excreta of the grazing animal, particularly the urine. This paper reviews published literature on the use of nitrification inhibitors (NI) to treat grazed pasture soils to mitigate NO3 − leaching and N2O emissions. This paper provides a review on: ammonia oxidisers, including ammonia oxidising bacteria (AOB) and ammonia oxidising archaea (AOA), that are responsible for ammonia oxidation in the urine patch areas of grazed pastures; the effectiveness of NIs, such as dicyandiamide (DCD) and 3,4-dimethylpyrazole phosphate (DMPP), in inhibiting the growth and activity of ammonia oxidisers; the efficacy of DCD and DMPP in reducing NO3 − leaching and N2O emissions in grazed pastures; additional benefits of using NI in grazed pasture, including increased pasture production, decreased cation leaching and decreased NO3 − concentrations in plants; and major factors that may affect the efficacy of NIs. Research from a number of laboratory and field studies have conclusively demonstrated that treating grazed pasture soils with a NI, such as DCD, is an effective means of reducing NO3 − leaching and N2O emissions from grazed livestock production systems. Results show that N2O emissions from animal urine-N can be reduced by an average of 57 % and NO3 − leaching from animal urine patches can be reduced by 30 to 50 %. The NI technology has been shown to be effective under a wide range of soil and environmental conditions. The NI technology also provides other benefits, including increased pasture production, reduced cation (Ca2+, Mg2+ and K+) leaching and reduced NO3 − concentration in pasture plants which would reduce the risk of NO3 − poisoning for the animal. The use of NIs such as DCD to treat grazed pasture soil is a scientifically sound and practically viable technology that can effectively mitigate NO3 − leaching and N2O emissions in grazed livestock production systems.

Temporal variability of soil microbial communities after application of dicyandiamide-treated swine slurry and mineral fertilizers

In modern agriculture, mineral and organic fertilization account for most of the global anthropogenic N2O emissions. A strategy to prevent or to reduce emissions of greenhouse gases such as N2O is the use of nitrification inhibitors, which temporarily inhibit the microbial conversion of soil ammonium to nitrate. However, information about the magnitude and duration of disturbance caused by organic fertilization with nitrification inhibitor on the microbial community is lacking. Here we examined N dynamics and how potentially active soil microbial communities changed through time by the addition of dicyandiamide-treated swine slurry and mineral fertilizers. A field experiment (corn/cereal succession under no-tillage system) was carried out using the following treatments: (I) unfertilized control, (II) surface application of mineral nutrients, (III) surface application of swine slurry, and (IV) surface application of swine slurry with dicyandiamide. Soil samples were collected at 0, 3, 6, 11, 25 and 50 days after start of experiment. Total RNA was extracted, synthesized to cDNA and used as template to amplify and sequence the 16S rRNA. Nitrous oxide emissions were also quantified. The organic fertilizers were the main drivers on changes in microbial community structure. Slurry application decreased microbial diversity and changed the microbial structure temporarily but the metabolically active microbial community was resilient, recovering to the original status 50 days post-fertilization. DCD had no effect on metabolically active microbial community and was pathway-specific, having impact only on nitrifiers during a short-term period, which in turn reduced the N2O emissions.

Rainfall amount and distribution regulate DMPP effects on nitrous oxide emissions under semiarid Mediterranean conditions

Nitrogen fertilizer application timing and the use of nitrification inhibitors are currently promoted as agronomic practices with potential to reduce nitrous oxide (N2O) emissions. However, the efficacy of these practices is to a large extent regulated by weather variability, particularly rainfall and temperature. This is primarily the case for rainfed crops under semiarid Mediterranean climate, where large fluctuations occur in the amount and frequency of rainfall from year to year. In this 3-year field experiment, we explored the potential of fertilizer application timing and a nitrification inhibitor (3,4-dimethyl pyrazole phosphate; DMPP) to achieve low N2O, for a rainfed barely (Hordeum vulgare L. cv Pedrezuela) crop under a semiarid Mediterranean climate. Five fertilizer management practices were tested: split fertilizer application at planting and at tillering with (1) or without DMPP (2); the same split fertilizations but applying DMPP only at tillering (3); and single fertilizer application al tillering with (4) or without DMPP (5). During the dry conditions of year 1, the application of DMPP reduced N2O emissions (up to 72%) whereas timing of fertilizer application had no effect. Conversely, under the wet conditions of year 2 the effect of DMPP was suppressed but fertilizer timing was successful diminishing N2O, with lower emissions measured with single fertilizer application at tillering. In year 3, where rainfall distribution was remarkably erratic, N2O emissions were mitigated by both DMPP and single fertilizer applications. Overall, our results show that DMPP offers an opportunity for N2O abatement in semiarid soils under Mediterranean environments. The low moisture content of these soils during long periods favors nitrification; by inhibiting this process, products such as DMPP are able to achieve large N2O reductions. Although single fertilizer application at tillering as opposed to the traditional split application at planting and tillering may provide a management opportunity for N2O mitigation, we also found that this practice may lead to yield reductions in years with sufficient rainfall in spring. Therefore, general implementation of this practice should not be encouraged.

Combined use of nitrification inhibitor and struvite crystallization to reduce the NH3 and N2O emissions during composting

Struvite crystallization (SCP) is combined with a nitrification inhibitor (dicyandiamide, DCD) to mitigate the NH3 and N2O emission during composting. The MgO and H3PO4 were added at a rate of 15% (mole/mole) of initial nitrogen, and the DCD was added at rates of 0%, 2.5%, 5.0%, 7.5% and 10% (w/w) of initial nitrogen respectively. Results showed that the combination use of SCP and DCD was phytotoxin free. The SCP could significantly reduce NH3 losses by 45–53%, but not the DCD. The DCD significantly inhibits nitrification when the content was higher than 50mgkg−1, and that could reduce the N2O emission by 76.1–77.6%. The DCD degraded fast during the thermophilic phase, as the nitrification will be inhibited by the high temperature and high free ammonia content in this stage, the DCD was suggested to be applied in the maturing periods by 2.5% of initial nitrogen.

Greenhouse gas emissions after application of digestate: short-term effects of nitrification inhibitor and application technique effects

ABSTRACTNitrogen-use efficiency in arable agriculture after organic fertilization can be improved by the incorporation of digestate into soil and through the use of nitrification inhibitors. To test the efficiency and the interaction of these measures, a laboratory microcosm study was conducted with undisturbed samples from two arable soils – a Gleysol and a Plaggic Anthrosol. Treatments were digestate application by injection to 15 or 20 cm depths or by trailing hose with subsequent incorporation. Half of the replicates of each application treatment were treated with the nitrification inhibitor 3,4-dimethyl pyrazole phosphate (DMPP). Emissions of the greenhouse gases (GHGs) CO2, N2O and CH4 were monitored during 51 days of incubation. Deeper injection (20 cm) did not lead to different GHG emissions compared with a shallow injection (15 cm). Application of DMPP decreased cumulative N2O emissions significantly by 17–70%. DMPP inhibited N2O fluxes and NO3- production, suggesting a positive effect of DMPP on the mitigation of direct GHG emission and nitrate leaching at least during several weeks after digestate fertilization. The effect of DMPP is independent of the application technique.

Plant acquisition and metabolism of the synthetic nitrification inhibitor dicyandiamide and naturally-occurring guanidine from agricultural soils

There is increasing interest and use of nitrification inhibitors (NI) in agroecosystems, yet little is known of their fate in planta. Residues of the organic, N-rich NI, dicyandiamide (DCD), have been found in milk products following commercial application to pasture. We investigated whether plant acquisition and metabolism of DCD were consistent with plant-mediated transmission from soil to agricultural food products. Uptake rates, translocation to the shoot, degradation of the label within wheat tissue and availability within two soils of DCD and the structurally similar naturally occurring N-rich molecule, guanidine, were measured using 14C labelling. Under sterile conditions, over 2 h wheat took up (34 and 14 μmol g−1 root DW h−1 at 1 mM: DCD and guanidine, respectively), translocated (7–15 and 19–22 %) and metabolised (0.4 and 0.9 % of uptake) DCD- and guanidine-14C. Both molecules were also acquired from soil by wheat despite concurrent soil sorption and microbial uptake. Both DCD and guanidine can be acquired and metabolised by graminaceous plants. Although probably not a significant route of N acquisition, plant uptake provides a direct route of DCD entry into the food chain.

Nitrous oxide emissions from pastures during wet and cold seasons

AbstractGrazed pastures contribute significantly to the global nitrous oxide (N2O) budget. In grazed pastures, the highest N2O emission rates are often reported during winter when soils are wet. This review discusses the current knowledge about factors controlling winter N2O emissions in grazed pastures. High N2O emissions from pastures during winter are also observed from winter‐housed animal feeding systems. At near‐zero temperature, N2O producing microbial activity is limited but some soil microbial communities adjust to low temperature better than others. Soil microbiological studies focusing on the identification of cold‐tolerant denitrifiers and/or changes in microbial community structures under cold conditions are required. In winter‐grazed pastures, the availability of substrates, such as nitrate () and labile organic carbon (C), for soil microbes producing N2O is influenced by factors such as animal wintering system, effluent management systems and plant activity. When animals are housed, N2O emissions during the winter storage of manures and the emissions after their application are important contributors to N2O inventories. The activity of pasture during winter and its relationship to N2O emissions requires further study in order to understand the competition between plants and N2O producing microbes for nitrogen, and the role of root exudation. Additionally, the effect of low temperatures on nutrient availability under urine patches is still not well known. The reduction of N2O to dinitrogen is regulated by an enzyme N2O reductase and its encoding gene (nosZ) expression needs to be studied in more detail to investigate the mechanisms behind winter N2O emissions. To mitigate N2O emissions during winter, restricted grazing regimes and the use of nitrification inhibitors have been studied; however, little is known about the effectiveness of these methods in mitigating N2O emissions during freeze/thaw cycles and during periods of snow‐cover.

Enhanced-Efficiency Fertilizers in Nitrous Oxide Emissions from Urea Applied to Sugarcane

The environmental benefits of producing biofuels from sugarcane have been questioned due to greenhouse gas emissions during the biomass production stage, especially nitrous oxide (NO) associated with nitrogen (N) fertilization. The objective of this work was to evaluate the use of nitrification inhibitors (NIs) dicyandiamide (DCD) and 3,4 dimethylpyrazole phosphate (DMPP) and a controlled-release fertilizer (CRF) to reduce NO emissions from urea, applied at a rate of 120 kg ha of N. Two field experiments in ratoon cycle sugarcane were performed in Brazil. The treatments were (i) no N (control), (ii) urea, (iii) urea+DCD, (iv) urea+DMPP, and (v) CRF. Measurements of NO fluxes were performed using static chambers with four replications. The measurements were conducted three times per week during the first 3 mo and biweekly afterward for a total of 217 and 382 d in the first and second seasons, respectively. The cumulative NO-N emissions in the first ratoon cycle were 1098 g ha in the control treatment and 1924 g ha with urea (0.7% of the total N applied). Addition of NIs to urea reduced NO emissions by more than 90%, which did not differ from those of the plots without N. The CRF treatment showed NO emissions no different from those of urea. The results were similar in the second ratoon: the treatment with urea showed NO emissions of 0.75% of N applied N. Application of NIs resulted in a strong reduction in NO emissions, but CRF increased emissions compared with urea. We therefore conclude that both NIs can be options for mitigation of greenhouse gas emission in sugarcane used for bioenergy.

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

AbstractThe 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 N2O 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$ _4^+ $ to NO$ _3^ - $ in soils. The inhibition of the AMO by NIs directly decreases the nitrification rate and it reduces the NO$ _3^- $ concentration which serves as substrate for denitrification. Hence, the two main pathways of N2O 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 NH3, results from literature suggest that the enzymatic activity of NH3 oxidizing bacteria is the most important target for NIs because it was much stronger affected. The application of NIs to reduce N2O 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 N2O 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 N2O 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$ _3^ - $ ‐ N leaching losses are reduced. It has clearly been demonstrated that NIs added to cattle slurry are very effective in reducing N2O as well as NO emissions after surface application and injection of slurry into grassland soils. In flooded rice systems NIs can reduce CH4 emission significantly, whereas the effect on CO2 emission is varying. On the other hand, as an effect of the delay of nitrification by NIs, NH3 emission might increase when N fertilizers are not incorporated into the soil. As compared to other measures NIs have a high potential to reduce N2O emissions from agricultural soils. Further, no other measure has so consistently been proofed according its efficiency to reduce N2O 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.

Rice production, nitrous oxide emission and ammonia volatilization as impacted by the nitrification inhibitor 2-chloro-6-(trichloromethyl)-pyridine

The effectiveness of nitrification inhibitor use in rice paddy fields is variable. In this regard, the impact of 2-chloro-6-(trichloromethyl)-pyridine (CP) nitrification inhibitor on rice yields and nitrogen (N) losses via nitrous oxide (N2O) emission and ammonia (NH3) volatilization from rice paddy fields was studied using five treatments: CK (no N applied), N180 and N240 (180kgNha−1 and 240kgNha−1 applied) and their counterparts N180+CP and N240+CP (N use plus CP). The field experiment was conducted in a major rice cultivation region of China in 2012 and 2013. The results showed that N180+CP increased rice yield by 10% in 2012 and 17% in 2013 compared with N180, and reached the same yield as N240. The N2O losses were 0.88% of N applied in 2012 and 0.38% in 2013 for N180, while they were reduced to 0.44% and 0.19% for N180+CP in the two years, respectively. For N240, CP decreased N2O losses from 0.78% to 0.71% in 2012 and from 0.38% to 0.22% in 2013. However, NH3 volatilization was increased by CP from 7.6% of applied N in N180 to 10.2% in N180+CP in 2012 and from 8.5% to 13.0% in 2013. The NH3 volatilization for N240 was increased by CP from 14.3% to 24.3% in 2012 and from 26.6% to 35.3% in 2013. Our results suggested that the decrease in N application was permitted by the use of CP since the same yield with 180kgNha−1 with CP was obtained as with 240kgNha−1 in the absence of CP and decreased direct emission of N2O. Despite the increase in NH3 volatilization with CP, and the consequent increase in indirect N2O emissions, we calculated that CP led to an overall decrease in global warming potential.

How inhibiting nitrification affects nitrogen cycle and reduces environmental impacts of anthropogenic nitrogen input

Anthropogenic activities, and in particular the use of synthetic nitrogen (N) fertilizer, have doubled global annual reactive N inputs in the past 50-100years, causing deleterious effects on the environment through increased N leaching and nitrous oxide (N2 O) and ammonia (NH3 ) emissions. Leaching and gaseous losses of N are greatly controlled by the net rate of microbial nitrification. Extensive experiments have been conducted to develop ways to inhibit this process through use of nitrification inhibitors (NI) in combination with fertilizers. Yet, no study has comprehensively assessed how inhibiting nitrification affects both hydrologic and gaseous losses of N and plant nitrogen use efficiency. We synthesized the results of 62 NI field studies and evaluated how NI application altered N cycle and ecosystem services in N-enriched systems. Our results showed that inhibiting nitrification by NI application increased NH3 emission (mean: 20%, 95% confidential interval: 33-67%), but reduced dissolved inorganic N leaching (-48%, -56% to -38%), N2 O emission (-44%, -48% to -39%) and NO emission (-24%, -38% to -8%). This amounted to a net reduction of 16.5% in the total N release to the environment. Inhibiting nitrification also increased plant N recovery (58%, 34-93%) and productivity of grain (9%, 6-13%), straw (15%, 12-18%), vegetable (5%, 0-10%) and pasture hay (14%, 8-20%). The cost and benefit analysis showed that the economic benefit of reducing N's environmental impacts offsets the cost of NI application. Applying NI along with N fertilizer could bring additional revenues of $163ha(-1) yr(-1) for a maize farm, equivalent to 8.95% increase in revenues. Our findings showed that NIs could create a win-win scenario that reduces the negative impact of N leaching and greenhouse gas production, while increases the agricultural output. However, NI's potential negative impacts, such as increase in NH3 emission and the risk of NI contamination, should be fully considered before large-scale application.

Managing greenhouse gas emissions in two major dairy regions of New Zealand: A system-level evaluation

New Zealand dairy farms are responsible for a large proportion of this nation's greenhouse gas emissions (GHG-e), arising mainly from enteric methane and urinary nitrogen deposition on pasture. De-intensification and the use of specific mitigation strategies can reduce GHG-e from dairy farms, but are generally costly. In this study, a farm-level model is used to analyse the cost of GHG-e mitigation strategies in medium- (10–20% imported feed) and high-input (20–40% imported feed) systems in the two major dairy regions of New Zealand (Waikato and Canterbury). Production intensity is measured solely in terms of feed importation, in accordance with standard practice in this nation. The focus of the study is to assess the cost-effectiveness of a variety of de-intensification and mitigation strategies aimed at reducing the negative impact of emissions constraints (reductions of 10, 20, and 30%) on farm profit. De-intensification options include changes in stocking rate, nitrogen fertiliser application, and supplement quantity. Mitigation options include feeding crops, improved reproductive management, use of feed pads, use of stand-off pads, and use of nitrification inhibitors. The model showed that a combination of reduced N fertiliser application and lower stocking rates were the larger changes experienced in the systems studied when GHG-e reductions were introduced. Nitrification inhibitors were only useful for mitigation once the GHG-e reductions required were so stringent that their cost was warranted to offset the significant costs associated with de-intensification in the high-input systems. Stand-off and feed pads were too expensive to warrant their use when not already available. Overall, de-intensification of the farming system proved to be more profitable than the use of specific mitigation practices when reduction of GHG-e was required. Maintaining a given intake of imported feed reduces the degree to which de-intensification may be used for abatement, thus inflating the cost of mitigation strategies on high-input farms.

Impact of nitrification inhibitor (DMPP) on soil nitrous oxide emissions from an intensive broccoli production system in sub-tropical Australia

Vegetable cropping systems are often characterised by high inputs of nitrogen fertiliser. Elevated emissions of nitrous oxide (N2O) can be expected as a consequence. In order to mitigate N2O emissions from fertilised agricultural fields, the use of nitrification inhibitors, in combination with ammonium based fertilisers, has been promoted. However, no data is currently available on the use of nitrification inhibitors in sub-tropical vegetable systems. A field experiment was conducted to investigate the effect of the nitrification inhibitor 3,4-dimethylpyrazole phosphate (DMPP) on N2O emissions and yield from broccoli production in sub-tropical Australia. Soil N2O fluxes were monitored continuously (3 h sampling frequency) with fully automated, pneumatically operated measuring chambers linked to a sampling control system and a gas chromatograph. Cumulative N2O emissions over the 5 month observation period amounted to 298 g-N/ha, 324 g-N/ha, 411 g-N/ha and 463 g-N/ha in the conventional fertiliser (CONV), the DMPP treatment (DMPP), the DMMP treatment with a 10% reduced fertiliser rate (DMPP-red) and the zero fertiliser (0N), respectively. The temporal variation of N2O fluxes showed only low emissions over the broccoli cropping phase, but significantly elevated emissions were observed in all treatments following broccoli residues being incorporated into the soil. Overall 70–90% of the total emissions occurred in this 5 weeks fallow phase. There was a significant inhibition effect of DMPP on N2O emissions and soil mineral N content over the broccoli cropping phase where the application of DMPP reduced N2O emissions by 75% compared to the standard practice. However, there was no statistical difference between the treatments during the fallow phase or when the whole season was considered. This study shows that DMPP has the potential to reduce N2O emissions from intensive vegetable systems, but also highlights the importance of post-harvest emissions from incorporated vegetable residues. N2O mitigation strategies in vegetable systems need to target these post-harvest emissions and a better evaluation of the effect of nitrification inhibitors over the fallow phase is needed.

Assessing biogeochemical effects and best management practice for a wheat–maize cropping system using the DNDC model

Abstract. Contemporary agriculture is shifting from a single-goal to a multi-goal strategy, which in turn requires choosing best management practice (BMP) based on an assessment of the biogeochemical effects of management alternatives. The bottleneck is the capacity of predicting the simultaneous effects of different management practice scenarios on multiple goals and choosing BMP among scenarios. The denitrification–decomposition (DNDC) model may provide an opportunity to solve this problem. We validated the DNDC model (version 95) using the observations of soil moisture and temperature, crop yields, aboveground biomass and fluxes of net ecosystem exchange of carbon dioxide, methane, nitrous oxide (N2O), nitric oxide (NO) and ammonia (NH3) from a wheat–maize cropping site in northern China. The model performed well for these variables. Then we used this model to simulate the effects of management practices on the goal variables of crop yields, NO emission, nitrate leaching, NH3 volatilization and net emission of greenhouse gases in the ecosystem (NEGE). Results showed that no-till and straw-incorporated practices had beneficial effects on crop yields and NEGE. Use of nitrification inhibitors decreased nitrate leaching and N2O and NO emissions, but they significantly increased NH3 volatilization. Irrigation based on crop demand significantly increased crop yield and decreased nitrate leaching and NH3 volatilization. Crop yields were hardly decreased if nitrogen dose was reduced by 15% or irrigation water amount was reduced by 25%. Two methods were used to identify BMP and resulted in the same BMP, which adopted the current crop cultivar, field operation schedules and full straw incorporation and applied nitrogen and irrigation water at 15 and 25% lower rates, respectively, than the current use. Our study indicates that the DNDC model can be used as a tool to assess biogeochemical effects of management alternatives and identify BMP.

Assessing the Influence of Summer Organic Fertilization Combined with Nitrogen Inhibitor on a Short Rotation Woody Crop in Mediterranean Environment

The European Union Directive 91/676/EEC, known as Nitrates Directive, has dictated basic agronomic principles regarding the use of animal manure source as well as livestock and waste waters from small food companies. The use of nitrification inhibitors together with animal effluents as organic fertilizers could be beneficial for nutrient recycling, plant productivity, and greenhouse gas emission and could offer economic advantages as alternative to conventional fertilizers especially in the Mediterranean region. The aim of the present study was to investigate differences in plant productivity between bovine effluent treatments with (or without) addition of a nitrification inhibitor (3,4 DMPP) in a short rotation woody crop system. Results of the field experiment carried out in a Mediterranean dry environment indicated that the proposed strategy could improve tree growth with indirect, beneficial effects for agroforestry systems.

Redução na velocidade da nitrificação no solo após aplicação de cama de aviário com dicianodiamida

A rápida nitrificação do nitrogênio (N) amoniacal de fontes orgânicas e minerais no solo pode resultar em perdas de nitrato (NO3-) para o ambiente. Uma estratégia para a redução dessas perdas envolve o uso de inibidores de nitrificação. O objetivo do presente trabalho foi o de avaliar, em condições de laboratório, a eficiência da dicianodiamida (DCD), presente no produto Agrotain® Plus (AP), em inibir a nitrificação do N amoniacal de cama de aviário (CA) no solo. Foram avaliados cinco tratamentos, sendo um com CA incorporada ao solo, três com CA incorporada ao solo com AP, nas doses de 3,5, 7,0 e 14,0kg ha-1, além de um tratamento somente com solo. A nitrificação foi monitorada através da determinação periódica dos teores de NH4+ e NO3 no solo durante 69 dias. A maior taxa de nitrificação ocorreu no tratamento em que a CA foi incorporada ao solo sem AP. As doses de 3,5 e 7,0kg de AP ha-1 inibiram parcialmente a nitrificação do N amoniacal da CA na fase inicial da incubação, perdendo a eficiência em inibir esse processo no período entre 12 e 27 dias. O tratamento com a maior dose de AP (14kg ha-1) foi aquele em que a DCD exerceu maior efeito inibitório da nitrificação, preservando maior quantidade de NH4+ e retardando o aparecimento de NO3- no solo. Os resultados deste trabalho indicam que a DCD, contida no Agrotain® Plus, reduz a taxa de nitrificação do N amoniacal da CA no solo, o que poderá contribuir à redução das perdas de NO3- para o ambiente.

Opportunities for reducing environmental emissions from forage-based dairy farms

Modern dairy production is inevitably associated with impacts to the environment and the challenge for the industry today is to increase production to meet growing global demand while minimising emissions to the environment. Negative environmental impacts include gaseous emissions to the atmosphere, of ammonia from livestock manure and fertiliser use, of methane from enteric fermentation and manure management, and of nitrous oxide from nitrogen applications to soils and from manure management. Emissions to water include nitrate, ammonium, phosphorus, sediment, pathogens and organic matter, deriving from nutrient applications to forage crops and/or the management of grazing livestock. This paper reviews the sources and impacts of such emissions in the context of a forage-based dairy farm and considers a number of potential mitigation strategies, giving some examples using the farm-scale model SIMSDAIRY. Most of the mitigation measures discussed are associated with systemic improvements in the efficiency of production in dairy systems. Important examples of mitigations include: improvements to dairy herd fertility, that can reduce methane and ammonia emissions by up to 24 and 17%, respectively; diet modification such as the use of high sugar grasses for grazing, which are associated with reductions in cattle N excretion of up to 20% (and therefore lower N losses to the environment) and potentially lower methane emissions, or reducing the crude protein content of the dairy cow diet through use of maize silage to reduce N excretion and methane emissions; the use of nitrification inhibitors with fertiliser and slurry applications to reduce nitrous oxide emissions and nitrate leaching by up to 50%. Much can also be achieved through attention to the quantity, timing and method of application of nutrients to forage crops and utilising advances made through genetic improvements.