3,4-Dimethylpyrazol phosphate effect on nitrous oxide, nitric oxide, ammonia, and carbon dioxide emissions from grasslands

Nitrification and urease inhibitors mitigate global warming potential and ammonia volatilization from urea in rice-wheat system in India: A field to lab experiment

The efficacy of alternative nitrogenous fertilizers for mitigating greenhouse gas and ammonia emissions from a rice-wheat cropping system in northern India was addressed in a laboratory incubation experiment using soil from a 10-year residue management field experiment (crop residue removal, CRR, vs. incorporation, CRI). Neem coated urea (NCU), standard urea (U), urea ammonium sulfate (UAS), and two alternative fertilizers, urea + urease inhibitor NBPT (UUI) and urea + urease inhibitor NBPT + nitrification inhibitor DMPSA (UUINI) were compared to non-fertilized controls for four weeks in incubation under anaerobic condition. Effects of fertilizers on global warming potential (GWP) and ammonia volatilization were dependent on residue treatment. Relative to standard urea, NCU reduced GWP by 11 % in CRI but not significantly in CRR; conversely, UAS reduced GWP by 12 % in CRR but not significantly in CRI. UUI and UUINI reduced GWP in both residue treatments and were more effective in CRI (21 % and 26 %) than CRR (15 % and 14 %). Relative to standard urea, NCU increased ammonia volatilization by 8 % in CRI but not significantly in CRR. Ammonia volatilization was reduced most strongly by UUI (40 % in CRI and 37 % in CRR); it was reduced 28-29 % by UUINI and 12-15 % by UAS. Overall, the urease inhibitor, alone and in combination with the nitrification inhibitor, was more effective in mitigating greenhouse gas and ammonia emissions than NCU. However, these products need to be tested in field settings to validate findings from the controlled laboratory experiment.

Effects of acidifiers on soil greenhouse gas emissions in calcareous soils in a semi-arid area

In most agricultural fields, when soil pH is high, elemental sulfur or sulfuric acid are used to reduce soil pH and increase the availability of macro and micronutrients for optimum crop yield. However, how these inputs impact soil greenhouse gas emissions is unknown. This study aimed to measure the amount of greenhouse gas emissions and pH after the application of various doses of elemental sulfur (ES) and sulfuric acid (SA). Using static chambers, this study quantifies soil greenhouse gas emissions (CO2, N2O, and CH4) for 12 months after the application of ES (200, 400, 600, 800, and 1000 kg ha−1) and SA (20, 40, 60, 80 and 100 kg ha−1) to a calcareous soil (pH 8.1) in Zanjan, Iran. Also, in order to simulate rainfed and dryland farming which are common practices in this area, this study was conducted with and without sprinkler irrigation. Application of ES slowly decreased soil pH (more than half a unit) over the year whereas application of SA temporarily reduced the pH (less than a half unit) for a few weeks. CO2 and N2O emissions and CH4 uptake were maximum during summer and lowest in winter. Cumulative CO2 fluxes ranged from 1859.2 kg−1 CO2-C ha−1 year−1 in the control treatment to 2269.6 kg CO2-C ha−1 year−1 in the 1000 kg ha−1 ES treatment. Cumulative fluxes for N2O-N were 2.5 and 3.7 kg N2O-N ha−1 year−1 and cumulative CH4 uptakes were 0.2 and 2.3 kg CH4-C ha−1 year−1 in the same treatments. Irrigation significantly increased CO2 and N2O emissions and, depending on the amount of ES applied, decreased or increased CH4 uptake. SA application had a negligible effect on GHGs emissions in this experiment and only the highest amount of SA altered GHGs emissions.

Impact of cattle slurry application methods on ammonia losses and grassland nitrogen use efficiency

Optimal manure management is required to ensure efficient nutrient supply to farmland and to avoid adverse environmental impacts. Accordingly, ammonia (NH₃) emissions associated with different slurry application techniques were investigated in grassland trials under different soil and weather conditions across Germany. Cattle slurry was applied in two dressings, early in spring and after the first silage cut, with a target amount of 170 kg N ha^-1. The application treatments comprised: trailing shoe (TS), acidified slurry applied with trailing shoe (TS + A), open slot injection (SI), and slurry treated with a nitrification inhibitor (NI) applied by slot injection (SI + NI). In addition, slurry application techniques were compared with a non-N-fertilized control and a mineral fertilizer treatment (calcium ammonium nitrate, CAN). NH₃ measurements followed each N application event. NH₃ losses were equivalent to 1-39% of total ammoniacal nitrogen (TAN) applied. The average NH₃ mitigation potential of the different slurry application techniques compared to TS was 45.7 ± 7, 21.2 ± 6.2 and 13.7 ± 8.2% for TS + A, SI and SI + NI, respectively. The use of nitrification inhibitor with slot injected slurry did not increase NH₃ losses relative to TS (p > 0.05). Mean apparent N use efficiency was two times higher for CAN (49%) than the slurry treatments (24%) but was comparable between SI + NI and CAN in five out of the eight cases. Our results indicate that mean TAN related NH₃ emissions of tested treatments (3.3, 22.6, 12.2, 17.8 and 19.3% for CAN, TS, TS + A, SI and SI + NI, respectively) were generally lower than described in previous studies. Moreover, the results suggested possible increases in NH₃ mitigation and N use efficiency when cattle slurry is applied with acidification or injection techniques. We found no evidence that NI addition to slot injected slurry, a treatment discussed as a measure to reduce N₂O emission and nitrate leaching, changed NH₃ emission.

Influences of split application and nitrification inhibitor on nitrogen losses, grain yield, and net income for summer maize production

The application of nitrogen (N) fertilizer combined with nitrification inhibitor is considered to be one of the effective strategies to improve N efficiency and reduce N loss. While the chemical and physical properties of nitrapyrin (CP) in fertilizers have been evaluated to increase N efficiency, a lack of comprehensive evaluation of the effects of adding CP on summer maize yield, environmental benefits and economic income under different fertilization methods. In this study, two fertilization methods were used: split-N application and one-time basal N fertilizer before sowing. The comprehensive effects of N fertilizer with CP on N loss (NH3 volatilization, NO3 - leaching, and N2O emissions), N efficiency, yield and profit under two N application methods were explored. Results showed that under the two N application methods, N fertilizer with CP treatment increased the N efficiency and yield (+3.4%∼+5.7%), significantly reduced the soil NO3 --N content and N2O emissions, while increased NH3 volatilization. Especially, the increase amplitude of NH3 was much less than the decrease amplitude of N2O induced by adding CP. Although split-N application could achieve higher yield and N efficiency, N2O emissions and NH3 volatilization also increased. However, the T1 + N (one-time basal N fertilizer before sowing mixed with CP) achieved the same yield level as T2 treatment (split-N application). Taking agronomic, economic and environmental benefits into consideration, one-time basal N fertilizer before sowing mixed with CP could ensure the target yield, increase economic benefits, maintain soil N content, and reduce N losses. Therefore, optimizing N management is essential to the sustainable development of agriculture.

Nitrapyrin Addition Mitigated CO2 Emission from a Calcareous Soil Was Closely Associated with Its Effect on Decreasing Cellulolytic Fungal Community Diversity

Application of nitrification inhibitors (NIs) has been widely used to inhibit nitrification and reduce N₂O emissions. However, the impacts of NI addition on soil carbon transformation and carbon-degrading microbial communities have not been well explored. Here, a microcosm experiment was carried out, and four treatments were designed: (i) unfertilized control, (ii) urea alone, (iii) urea plus cattle manure, and (iv) urea plus cattle manure with nitrapyrin. The influence of nitrapyrin on soil CO₂ emissions, carbon-degrading extracellular enzyme activities, and the abundance and diversity of the cbhI community was investigated. Compared to the treatment of urea plus cattle manure, nitrapyrin significantly decreased cumulative CO₂ emissions by 51.8%. Moreover, cbhI community gene copies and their α-diversities (P < 0.05) were also significantly reduced by nitrapyrin application. A partial least squares path model showed that CO₂ emission was positively associated with cbhI community α-diversity but negatively associated with nitrapyrin addition. We conclude that the mitigation of soil CO₂ emissions by nitrapyrin can be ascribed to its effects on decreasing of cellulose-degrading gene community diversity. Our findings provide new insights into the side-effects of nitrapyrin on abating CO₂ emission.

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.

Ammonia volatilisation from pig slurry and ANS with DMPP applied to Westerwold ryegrass (Lolium multiflorum Lam., cv. Trinova) under Mediterranean conditions

Ammonia volatilisation from agriculture represents an important nitrogen (N) loss which has both environmental and economic impacts. In regions where large amounts of manures are available, there is a need to find appropriate management strategies that help to reuse them without increasing ammonia volatilisation. A study was made of the effect on ammonia volatilisation and yield of fertilising ryegrass with pig slurry (PS) and ammonium nitrosulphate (ANS-26) alone and with the 3,4-dimethylpyrazol phosphate (DMPP) nitrification inhibitor added to them. The study was conducted under Mediterranean conditions at two different sites. The treatments (control, PS, PS + DMPP, ANS-26 and ENTEC®) were established in a randomised block design with three replicates. Ammonia was sampled daily after each fertilisation using semi-static volatilisation chambers. We hypothesised that PS could replace mineral fertiliser without substantially increasing ammonia volatilisation in the studied systems. Temperature positively correlated with ammonia emissions. On the whole, during the two years of the study, the PS treatments presented higher average cumulative ammonia volatilisation (25% of total ammonium nitrogen (TAN) applied at Site 1; 21% of TAN applied at Site 2) than the mineral ones (11% of TAN applied at Site 1; 10% of TAN applied at Site 2). At pre-sowing, ammonia volatilisation was significantly (p < .05) lower (51% at Site 1; 55% at Site 2) than after ryegrass cuts due to burying PS immediately after application. Overall, applying DMPP had no effect on ammonia volatilisation. There were no significant differences in average yield (from 13.7 to 15.8 kg ha^-1 at Site 1; from 11.6 to 13.5 kg ha^-1 at Site 2) between the fertilised treatments, though ENTEC® tended to increase it. Applying PS (pre-sowing fertilisation) in combination with mineral N or processed PS fractions after ryegrass cuts could be an interesting option for the recycling of this livestock by-product without increasing ammonia volatilisation while maintaining yields.

Relationship between tillage management and DMPSA nitrification inhibitor efficiency

Agricultural sustainability is compromised by nitrogen (N) losses caused by soil microbial activity. Nitrous oxide (N₂O) is a potent greenhouse gas (GHG) produced as consequence of nitrification and denitrification processes in soils. Nitrification inhibitors (NI) as 3,4-dimethylpyrazole-succinic acid (DMPSA) are useful tools to reduce these N losses from fertilization. The objective of this work was to test the efficiency of DMPSA in two different tillage management systems, conventional tillage (CT) and no-tillage (NT), in a winter wheat crop under Humid Mediterranean conditions. N fertilizer was applied as ammonium sulphate (AS) with or without DMPSA in a single or split application, including an unfertilized treatment. GHG fluxes (N₂O, CO₂ and CH₄) were measured by the closed chamber method. amoA and nosZI genes were quantified by qPCR as indicators of nitrifying and denitrifying populations. Nitrification was inhibited by DMPSA in both CT and NT, while the higher water filled pore space (WFPS) in NT promoted a better efficiency of DMPSA in this system. This higher efficiency might be due to a greater N₂O reduction to N₂ as result of the nosZI gene induction. Consequently, DMPSA was able to reduce N₂O emissions down to the unfertilized levels in NT. Provided that NT reduced CO₂ emissions and maintained crop yield compared to CT, the application DMPSA under NT management is a promising strategy to increase agro-systems sustainability under Humid Mediterranean conditions.

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

Nitrification inhibitors (NIs) have been shown to reduce emissions of the greenhouse gas nitrous oxide (N₂O) from agricultural soils. However, their N₂O reduction efficacy varies widely across different agro-ecosystems, 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 N₂ and N₂O emissions with ¹⁵N tracing analysis and the quantification of the N₂O-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 N₂O is responsible for large pulses of N₂O after the fertilization of agricultural soils. DMPP attenuated this effect only in the horticultural soil, reducing nitrification while increasing nosZ abundance. DMPP reduced N₂O emissions from the horticultural soil by >50% but did not affect overall N₂ + N₂O losses, demonstrating the shift in the N₂O:N₂ ratio towards N₂ as a key mechanism of N₂O mitigation by NIs. Under non-limiting NO₃⁻ availability, the efficacy of NIs to mitigate N₂O emissions therefore depends on their ability to reduce the suppression of the N₂O reductase by high NO₃⁻ concentrations in the soil, enabling complete denitrification to N₂.

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.

Effects of nitrogen loading on emission of carbon gases from estuarine tidal marshes with varying salinity

Estuarine tidal marshes sequester significant quantities of carbon and are suffering from anthropogenic nitrogen (N) enhancement. However, the effects of this N loading on carbon gas emissions from freshwater-oligohaline tidal marshes are unknown. In this paper, we report on our evaluation of the effects of a N gradient (0, 24, 48 and 96 g NH₄NO₃-N m^-2 y^-1) on the methane (CH₄) and carbon dioxide (CO₂) emissions from freshwater and oligohaline tidal marshes in the Min River estuary, southeast China. On an annual scale, the oligohaline marsh has significantly higher CO₂ emissions, while it has slightly lower CH₄ emissions relative to freshwater marsh. The addition of N increased CH₄ emission from the freshwater marsh and decreased CH₄ emission from the oligohaline marsh, although there was no statistically significant difference in CH₄ emission between either of the two marshes and the control. The addition of 96 g NH₄NO₃-N m^-2 y^-1 significantly increased CO₂ emission from the freshwater marsh, while it did not significantly influence CO₂ emission from the oligohaline marsh. CH₄ and CO₂ emission levels were positively correlated with soil temperature under all conditions. The CH₄ flux resulting from both the control and the addition of N was negatively correlated with porewater SO₄^2- and Cl^- concentrations and soil EC in the oligohaline marsh. Overall, N addition significantly increased carbon gas emissions under freshwater conditions while slightly inhibiting carbon gas emissions from the oligohaline marsh. Our findings suggested that even under low salinity conditions, the effects of N loading on CH₄ and CO₂ emissions from freshwater and oligohaline tidal marshes can vary. We propose that the addition of N to estuarine tidal marshes has a significant effect on the carbon cycle and promotes soil carbon loss, phenomena which may be influenced by salinity.

Producing more grain yield of rice with less ammonia volatilization and greenhouse gases emission using slow/controlled-release urea

Ammonia (NH₃) volatilization and greenhouse gas (GHG) emission from rice (Oryza sativa L.) fields contaminate the atmospheric environment and lead to global warming. Field trials (2013-2015) were conducted to estimate the influences of different types of fertilization practices on grain yield, NH₃ volatilization, and methane (CH₄) and nitrous oxide (N₂O) emissions in a double rice cropping system in Central China. Results showed that grain yields of rice were improved significantly by using slow/controlled-release urea (S/C-RU). Compared with farmers' fertilizer practice (FFP) treatment, average annual grain yield with application of polymer-coated urea (CRU), nitrapyrin-treated urea (CP), and urea with effective microorganism (EM) treatments was increased by 18.0%, 16.2%, and 15.4%, respectively. However, the effects on NH₃ volatilization and CH₄ and N₂O emissions differed in diverse S/C-RU. Compared with that of the FFP treatment, the annual NH₃ volatilization, CH₄ emission, and N₂O emissions of the CRU treatment were decreased by 64.8%, 19.7%, and 35.2%, respectively; the annual CH₄ and N₂O emissions of the CP treatment were reduced by 33.7% and 40.3%, respectively, while the NH₃ volatilization was increased by 18.5%; the annual NH₃ and N₂O emissions of the EM treatment were reduced by 6.3% and 28.7%, while the CH₄ emission was improved by 4.3%. Overall, CP showed the best emission reduction with a decrement of 34.3% in global warming potential (GWP) and 44.4% in the greenhouse gas intensity (GHGI), followed by CRU treatment with a decrement of 21.1% in GWP and 31.7% in GHGI, compared with that of the FFP treatment. Hence, it is suggested that polymer-coated urea can be a feasible way of mitigating NH₃ volatilization and CH₄ and N₂O emission from rice fields while maintaining or increasing the grain yield in Chinese, the double rice cropping system.

3,4-Dimethylpyrazole phosphate and 2-(N-3,4-dimethyl-1H-pyrazol-1-yl) succinic acid isomeric mixture nitrification inhibitors: Quantification in plant tissues and toxicity assays

Nitrification inhibitors are used to maintain ammonium available in the soil for longer periods while reducing nitrate leaching and N₂O emission. In this work we evaluated the potential toxicity effects of 3,4-dimethylpyrazole phosphate (DMPP) and 2-(N-3,4-dimethyl-1H-pyrazol-1-yl) succinic acid isomeric mixture (DMPSA) nitrification inhibitors. In order to determine the potential plant capacity to take up and translocate these inhibitors, we grew clover plants in hydroponic conditions and we developed a novel methodology for extracting DMPP and DMPSA that we quantified by HPLC. In addition, we also did toxicity bioassays: seed germination and Vibrio fischeri test. When clover was exposed to high amounts of nitrification inhibitors, plants accumulated DMPP, predominantly in leaves, and also DMPSA that preferentially accumulated in roots. These inhibitors did not provoke phytotoxicity at the equivalent of the maximum amount estimated in agriculture (0.5mg/kg soil). DMPP only provoked detrimental effects in plants at very high dose (100mg/kg soil). Interestingly, DMPSA was innocuous.

Quantifying the contribution of riparian soils to the provision of ecosystem services

Riparian areas, the interface between land and freshwater ecosystems, are considered to play a pivotal role in the supply of regulating, provisioning, cultural and supporting services. Most previous studies, however, have tended to focus on intensive agricultural systems and only on a single ecosystem function. Here, we present the first study which attempts to assess a wide range of ecological processes involved in the provision of the ecosystem service of water quality regulation across a diverse range of riparian typologies. Specifically, we focus on 1) evaluating the spatial variation in riparian soils properties with respect to distance with the river and soil depth in contrasting habitat types; 2) gaining further insights into the underlying mechanisms of pollutant removal (i.e. pesticide sorption/degradation, denitrification, etc.) by riparian soils; and 3) quantify and evaluate how riparian vegetation across different habitat types contribute to the provision of watercourse shading. All the habitats were present within a single large catchment and included: (i) improved grassland, (ii) unimproved (semi-natural) grassland, (iii) broadleaf woodland, (iv) coniferous woodland, and (iv) mountain, heath and bog. Taking all the data together, the riparian soils could be statistically separated by habitat type, providing evidence that they deliver ecosystem services to differing extents. Overall, however, our findings seem to contradict the general assumption that soils in riparian area are different from neighbouring (non-riparian) areas and that they possess extra functionality in terms of ecosystem service provision. Watercourse shading was highly habitat specific and was maximal in forests (ca. 52% shade cover) in comparison to the other habitat types (7-17%). Our data suggest that the functioning of riparian areas in less intensive agricultural areas, such as those studied here, may be broadly predicted from the surrounding land use, however, further research is required to critically test this across a wider range of ecosystems.

Assessment of N2O emissions from a fertilised vegetable cropping soil under different plant residue management strategies using 15N tracing techniques

Combined application of plant residues and N fertilisers strongly affect soil mineral N dynamics and N₂O emissions depending on the quality of the plant residues, their application methods and other management strategies. We investigated the effect of combined application of two vegetable plant residues (cauliflower and sweet corn) and ¹⁵N fertiliser on N dynamics and N₂O emission in a glasshouse pot study. The experiment was conducted under two residue management practices (soil incorporation vs surface mulching) over 98days with growing basil (Ocimum basilicum) plants. We also assessed the efficacy of applying the nitrification inhibitor, 3,4-dimethylpyrazole phosphate (DMPP) to the plant residues, for reducing N loss and mitigating N₂O emissions. Application of plant residues, both on the soil surface or into soil, resulted in net N mineralisation and increased cumulative N₂O emission compared with the application of N fertiliser alone. Soil surface mulching of sweet corn decreased total and residue-induced cumulative N₂O emission compared with the incorporation method, while it showed opposite effect on N₂O emissions from cauliflower residue. The application of DMPP with sweet corn residue reduced total, residue- and fertiliser-induced N₂O emissions; however its application with cauliflower residue did not show any mitigating effect on the N₂O emissions. The residue application methods and the use of DMPP did not significantly affect ¹⁵N recovery by the basil plants. In contrast, soil incorporation of these residues doubled the microbial immobilisation of applied ¹⁵N into soil organic matter. Linear regression analysis of N₂O emission during the experimental period indicated that in the treatments without DMPP application, soil NO₃^--N concentration was the most important factor in controlling the magnitude of N₂O emissions, while the application of DMPP changed the dominant regulating factor from NO₃^--N to NH₄⁺-N concentration.

Dimethyl pyrazol-based nitrification inhibitors effect on nitrifying and denitrifying bacteria to mitigate N2O emission

Nitrous oxide (N2O) emissions have been increasing as a result of intensive nitrogen (N) fertilisation. Soil nitrification and denitrification are the main sources of N2O, and the use of ammonium-based fertilisers combined with nitrification inhibitors (NIs) could be useful in mitigating N2O emissions from agricultural systems. In this work we looked at the N2O mitigation capacity of two dimethylpyrazol-based NIs, 3,4-dimethylpyrazole phosphate (DMPP) and 2-(N-3,4-dimethyl-1H-pyrazol-1-yl) succinic acid isomeric mixture (DMPSA), on soil nitrifying and denitrifying microbial populations under two contrasting soil water contents (40% and 80% soil water filled pore space; WFPS). Our results show that DMPP and DMPSA are equally efficient at reducing N2O emissions under 40% WFPS conditions by inhibiting bacterial ammonia oxidation. In contrast, at 80% WFPS DMPSA was less efficient than DMPP at reducing N2O emissions. Interestingly, at 80% WFPS, where lowered oxygen availability limits nitrification, both DMPP and DMPSA not only inhibited nitrification but also stimulated N2O reduction to molecular nitrogen (N2) via nitrous oxide reductase activity (Nos activity). Therefore, in this work we observed that DMP-based NIs stimulated the reduction of N2O to N2 by nitrous oxide reductase during the denitrification process.

Inhibitory Effects of 3,4-Dimethylpyrazole Phosphate on CH4 and N2O Emissions in Paddy Fields of Subtropical China

3,4-Dimethylpyrazole phosphate (DMPP) has been widely employed to reduce nitrogen leaching and greenhouse gas emissions in the soils of dry farmlands. However, the effects of DMPP on the dynamics of nitrogen in paddy fields remain unclear. For this study, treatments with 0%, 0.25%, 0.5%, 1%, or 1.5% DMPP levels of nitrogen fertilization plus urea were designed to determine the effects on greenhouse gas emissions in paddy fields of subtropical China. All DMPP treatments significantly reduced CH4 and N2O emissions, from 54% to 34%, and 94% to 39%, respectively, compared with a urea fertilizer treatment alone. The soil NH4+ content decreased and NO3- increased more slowly with the application of DMPP. The crop yields under the various DMPP treatments showed no significant difference (p < 0.05). We concluded that the application of 0.5% and 1% DMPP may significantly reduce CH4 and N2O emissions in contrast to other treatments. This has important implications for the maintenance of rice yields, while reducing greenhouse gas emissions in paddy fields.

Using nitrification inhibitors to mitigate agricultural N2 O emission: a double-edged sword?

Nitrification inhibitors show promise in decreasing nitrous oxide (N₂ O) emission from agricultural systems worldwide, but they may be much less effective than previously thought when both direct and indirect emissions are taken into account. Whilst nitrification inhibitors are effective at decreasing direct N₂ O emission and nitrate (NO₃^- ) leaching, limited studies suggest that they may increase ammonia (NH₃ ) volatilization and, subsequently, indirect N₂ O emission. These dual effects are typically not considered when evaluating the inhibitors as a climate change mitigation tool. Here, we collate results from the literature that simultaneously examined the effects of nitrification inhibitors on N₂ O and NH₃ emissions. We found that nitrification inhibitors decreased direct N₂ O emission by 0.2-4.5 kg N₂ O-N ha^-1 (8-57%), but generally increased NH₃ emission by 0.2-18.7 kg NH₃ -N ha^-1 (3-65%). Taking into account the estimated indirect N₂ O emission from deposited NH₃ , the overall impact of nitrification inhibitors ranged from -4.5 (reduction) to +0.5 (increase) kg N₂ O-N ha^-1 . Our results suggest that the beneficial effect of nitrification inhibitors in decreasing direct N₂ O emission can be undermined or even outweighed by an increase in NH₃ volatilization.

Effects of the addition of nitrogen and sulfate on CH4 and CO2 emissions, soil, and pore water chemistry in a high marsh of the Min River estuary in southeastern China

Exogenous nitrogen (N) and sulfate (SO₄^2-), resulting from human activity, can strongly influence the emission of CH₄ and CO₂ from soil ecosystems. Studies have reported the effects of N and SO₄^2- on CH₄ and CO₂ emissions from inland peatlands and paddies. However, very few studies have presented year-round data on the effects of the addition of N and SO₄^2- on CH₄ and CO₂ emissions in estuarine marshes. The effects of the addition of N and SO₄^2- on the emission of CH₄ and CO₂ were investigated in a Cyperus malaccensis marsh in the high tidal flat of the Min River estuary of southeastern China from September 2014 to August 2015. Dissolved NH₄Cl, KNO₃, and K₂SO₄ were applied every month, in doses of 24gN/SO₄^2-m^-2·yr^-1. The emission of CH₄ and CO₂ showed distinct monthly and seasonal variations. Compared with the control, the addition of NH₄Cl and NH₄NO₃+K₂SO₄ showed increases in CH₄ fluxes (p<0.05), while the effects of the addition of KNO₃ and K₂SO₄ on CH₄ were minor (p>0.05). NH₄Cl had a positive impact on CO₂ emissions (p<0.01), while the addition of KNO₃, K₂SO₄, and NH₄NO₃+K₂SO₄ had minor positive impacts, compared to the control (p>0.05). Correlation analysis found that soil sulfate concentration, nitrogen availability and enzyme activity were the dominant factors influencing CH₄ and CO₂ variation. Our findings suggest that CH₄ and CO₂ emissions were influenced more by ammonium than by nitrate. We propose that the suppressive effect of additional sulfate on CH₄ production is insignificant, due to which the inhibition may be overestimated in the estuarine brackish marsh.

No tillage and liming reduce greenhouse gas emissions from poorly drained agricultural soils in Mediterranean regions

No tillage (NT) has been associated to increased N2O emission from poorly drained agricultural soils. This is the case for soils with a low permeable Bt horizon, which generates a perched water layer after water addition (via rainfall or irrigation) over a long period of time. Moreover, these soils often have problems of acidity and require liming application to sustain crop productivity; changes in soil pH have large implications for the production and consumption of soil greenhouse gas (GHG) emissions. Here, we assessed in a split-plot design the individual and interactive effects of tillage practices (conventional tillage (CT) vs. NT) and liming (Ca-amendment vs. not-amendment) on N2O and CH4 emissions from poorly drained acidic soils, over a field experiment with a rainfed triticale crop. Soil mineral N concentrations, pH, temperature, moisture, water soluble organic carbon, GHG fluxes and denitrification capacity were measured during the experiment. Tillage increased N2O emissions by 68% compared to NT and generally led to higher CH4 emissions; both effects were due to the higher soil moisture content under CT plots. Under CT, liming reduced N2O emissions by 61% whereas no effect was observed under NT. Under both CT and NT, CH4 oxidation was enhanced after liming application due to decreased Al(3+) toxicity. Based on our results, NT should be promoted as a means to improve soil physical properties and concurrently reduce N2O and CH4 emissions. Raising the soil pH via liming has positive effects on crop yield; here we show that it may also serve to mitigate CH4 emissions and, under CT, abate N2O emissions.

Effects of the Nitrification Inhibitor 3,4-Dimethylpyrazole Phosphate on Nitrification and Nitrifiers in Two Contrasting Agricultural Soils

The nitrification inhibitor 3,4-dimethylpyrazole phosphate (DMPP) is a powerful tool that can be used to promote nitrogen (N) use efficiency and reduce N losses from agricultural systems by slowing nitrification. Mounting evidence has confirmed the functional importance of ammonia-oxidizing archaea (AOA) and ammonia-oxidizing bacteria (AOB) in nitrification and N2O production; however, their responses to DMPP amendment and the microbial mechanisms underlying the variable efficiencies of DMPP across different soils remain largely unknown. Here we compared the impacts of DMPP on nitrification and the dynamics of ammonia oxidizers between an acidic pasture soil and an alkaline vegetable soil using a (15)N tracing and (13)CO2-DNA-stable-isotope probing (SIP) technique. The results showed that DMPP significantly inhibited nitrification and N2O production in the vegetable soil only, and the transient inhibition was coupled with a significant decrease in AOB abundance. No significant effects on the community structure of ammonia oxidizers or the abundances of total bacteria and denitrifiers were observed in either soil. The (15)N tracing experiment revealed that autotrophic nitrification was the predominant form of nitrification in both soils. The (13)CO2-DNA-SIP results indicated the involvement of AOB in active nitrification in both soils, but DMPP inhibited the assimilation of (13)CO2 into AOB only in the vegetable soil. Our findings provide evidence that DMPP could effectively inhibit nitrification through impeding the abundance and metabolic activity of AOB in the alkaline vegetable soil but not in the acidic pasture soil, possibly due to the low AOB abundance or the adsorption of DMPP by organic matter.

IMPORTANCE

The combination of the (15)N tracing model and (13)CO2-DNA-SIP technique provides important evidence that the nitrification inhibitor DMPP could effectively inhibit nitrification and nitrous oxide emission in an alkaline soil through influencing the abundance and metabolic activity of AOB. In contrast, DMPP amendment has no significant effect on nitrification or nitrifiers in an acidic soil, potentially owing to the low abundance of AOB and the possible adsorption of DMPP by organic matter. Our findings have direct implications for improved agricultural practices through utilizing the nitrification inhibitor DMPP in appropriate situations, and they emphasize the importance of microbial communities to the efficacy of DMPP.

Short-term effect of nitrogen addition on nitric oxide emissions from an alpine meadow in the Tibetan Plateau

Little information is available on nitric oxide (NO) fluxes from alpine ecosystems. We measured NO fluxes in control and nitrogen (N) addition (NH4NO3, 6 g N m(-2) year(-1)) plots from early June through October 2013 in an alpine meadow on the Tibetan Plateau, China. During the sample period, NO fluxes varied from -0.71 to 3.12 ug m(-2) h(-1) and -0.46 to 7.54 ug m(-2) h(-1) for control and N treatment plots. The mean NO emission in N addition plots (1.68 ug m(-2) h(-1)) was 2.15 times higher than the control plots (0.78 ug m(-2) h(-1)), indicating that alpine meadows may be a source of atmospheric NO, and N additions stimulated NO flux. A positive correlation was found between NO flux and soil temperature, water-filled pore space (WFPS), nitrate (NO3 (-)-N) content but no correlation with soil ammonium (NH4 (+)-N). These results suggest that denitrification is a principal process producing NO flux from alpine meadows.

Efficiency of two nitrification inhibitors (dicyandiamide and 3, 4-dimethypyrazole phosphate) on soil nitrogen transformations and plant productivity: a meta-analysis

Dicyandiamide (DCD) and 3, 4-dimethypyrazole phosphate (DMPP) are often claimed to be efficient in regulating soil N transformations and influencing plant productivity, but the difference of their performances across field sites is less clear. Here we applied a meta-analysis approach to compare effectiveness of DCD and DMPP across field trials. Our results showed that DCD and DMPP were equally effective in altering soil inorganic N content, dissolve inorganic N (DIN) leaching and nitrous oxide (N2O) emissions. DCD was more effective than DMPP on increasing plant productivity. An increase of crop yield by DMPP was generally only observed in alkaline soil. The cost and benefit analysis (CBA) showed that applying fertilizer N with DCD produced additional revenues of $109.49 ha(-1) yr(-1) for maize farms, equivalent to 6.02% increase in grain revenues. In comparisons, DMPP application produced less monetary benefit of $15.67 ha(-1) yr(-1). Our findings showed that DCD had an advantage of bringing more net monetary benefit over DMPP. But this may be weakened by the higher toxicity of DCD than DMPP especially after continuous DCD application. Alternatively, an option related to net monetary benefit may be achieved through applying DMPP in alkaline soil and reducing the cost of purchasing DMPP products.

Effect of irrigation, nitrogen application, and a nitrification inhibitor on nitrous oxide, carbon dioxide and methane emissions from an olive (Olea europaea L.) orchard

Drip irrigation combined with nitrogen (N) fertigation is applied in order to save water and improve nutrient efficiency. Nitrification inhibitors reduce greenhouse gas emissions. A field study was conducted to compare the emissions of nitrous oxide (N2O), carbon dioxide (CO2) and methane (CH4) associated with the application of N fertiliser through fertigation (0 and 50kgNha(-1)), and 50kgNha(-1)+nitrification inhibitor in a high tree density Arbequina olive orchard. Spanish Arbequina is the most suited variety for super intensive olive groves. This system allows reducing production costs and increases crop yield. Moreover its oil has excellent sensorial features. Subsurface drip irrigation markedly reduced N2O and N2O+N2 emissions compared with surface drip irrigation. Fertiliser application significantly increased N2O+N2, but not N2O emissions. Denitrification was the main source of N2O. The N2O losses (calculated as emission factor) ranging from -0.03 to 0.14% of the N applied, were lower than the IPCC (2007) values. The N2O+N2 losses were the largest, equivalent to 1.80% of the N applied, from the 50kgNha(-1)+drip irrigation treatment which resulted in water filled pore space >60% most of the time (high moisture). Nitrogen fertilisation significantly reduced CO2 emissions in 2011, but only for the subsurface drip irrigation strategies in 2012. The olive orchard acted as a net CH4 sink for all the treatments. Applying a nitrification inhibitor (DMPP), the cumulative N2O and N2O+N2 emissions were significantly reduced with respect to the control. The DMPP also inhibited CO2 emissions and significantly increased CH4 oxidation. Considering global warming potential, greenhouse gas intensity, cumulative N2O emissions and oil production, it can be concluded that applying DMPP with 50kgNha(-1)+drip irrigation treatment was the best option combining productivity with keeping greenhouse gas emissions under control.

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.

Do cover crops enhance N₂O, CO₂ or CH₄ emissions from soil in Mediterranean arable systems?

This study evaluates the effect of planting three cover crops (CCs) (barley, Hordeum vulgare L.; vetch, Vicia villosa L.; rape, Brassica napus L.) on the direct emission of N₂O, CO₂ and CH₄ in the intercrop period and the impact of incorporating these CCs on the emission of greenhouse gas (GHG) from the forthcoming irrigated maize (Zea mays L.) crop. Vetch and barley were the CCs with the highest N₂O and CO₂ losses (75 and 47% increase compared with the control, respectively) in the fallow period. In all cases, fluxes of N₂O were increased through N fertilization and the incorporation of barley and rape residues (40 and 17% increase, respectively). The combination of a high C:N ratio with the addition of an external source of mineral N increased the fluxes of N₂O compared with -Ba and -Rp. The direct emissions of N₂O were lower than expected for a fertilized crop (0.10% emission factor, EF) compared with other studies and the IPCC EF. These results are believed to be associated with a decreased NO₃(-) pool due to highly denitrifying conditions and increased drainage. The fluxes of CO₂ were in the range of other fertilized crops (i.e., 1118.71-1736.52 kg CO₂-Cha(-1)). The incorporation of CC residues enhanced soil respiration in the range of 21-28% for barley and rape although no significant differences between treatments were detected. Negative CH₄ fluxes were measured and displayed an overall sink effect for all incorporated CC (mean values of -0.12 and -0.10 kg CH₄-Cha(-1) for plots with and without incorporated CCs, respectively).

Effect of cattle slurry pre-treatment by separation and addition of nitrification inhibitors on gaseous emissions and N dynamics: a laboratory study

The application of untreated or treated animal manure to soils can result in increased N and C gaseous emissions contributing to ecosystem change and global warming. In the present study, dairy cattle slurry (liquid manure) was subjected first to pre-treatment by separation using a screw press to obtain a liquid (LF) and a solid fraction (SF). Then, the different fractions and the whole slurry (WS) were combined with two nitrification inhibitors (NI), dicyandiamide (DCD) or 3,4-dimethylpyrazole phosphate (DMPP), were applied to soil to assess the effect of slurry treatment by separation and NI addition on soil N dynamics and CH4, CO2, NH3, NO and N2O emissions. The WS and the two slurry fractions, combined or not with DCD or DMPP, were applied to soil at an equivalent field dosage of 120 kg total N ha(-1). Controls including a soil only, soil-DCD and soil-DMPP treatments were also included. The mixtures were incubated for 93-d at 20 degrees C. Results obtained show that NI inhibited nitrification between 16 and 30-d in WS and LF, with DMPP having a longer effect over time compared to DCD. There was no significant effect of NI on nitrification for the SF treatment. Nitrification inhibitors did not significantly affect (P>0.05) the CH4, CO2 and N2O emissions, but significantly decreased (P<0.05) NO emissions. Furthermore, the two NIs had a similar effect on gaseous emissions. Throughout the entire experiment, the greatest amount of NO was released from the LF treatment (without NI), while the greatest amount of N2O was released from the SF treatment. Slurry separation had no impact on N emissions, while the combination of this process with one of the two NI led to a small reduction in total N emissions.

Mineral-nitrogen leaching and ammonia volatilization from a rice-rapeseed system as affected by 3,4-dimethylpyrazole phosphate

3,4-Dimethylpyrazole phosphate (DMPP) was validated as an effective nitrification inhibitor to reduce nitrate leaching. Its effects on ammonia (NH(3)) volatilization were not clear, especially on farmland scale with crop rotations. In this study, on-farm experiments at the Jiaxing (JX) and Yuhang (YH) sites in Taihu Lake Basin, China were conducted to evaluate the effect of DMPP application on mineral nitrogen (N) (NH(4)-N and NO(3)-N) leaching and NH(3) volatilization losses in a rice-rapeseed cropping system. Treatments included urea alone (UA), urea + 1% DMPP (UD), and no fertilizer (CK). The results show that DMPP reduced NO(3)-N leaching fluxes by 44.9 to 59.9% and increased NH(4)-N leaching fluxes by 13.0 to 33.3% at two sites during rice and rape seasons compared with urea alone. Reductions in mineral-N leaching fluxes by DMPP in two seasons at the JX and YH sites were 9.5 and 14.3 kg N ha(-1), respectively, compared with UA treatment. The application of DMPP had no significant effects on NH(3) volatilization loss fluxes at either site. The rice and rapeseed yields were 5.3 to 7.4% higher in UD plots than in UA plots at two sites. These results that indicate DMPP could reduce leaching losses of mineral-N from crop fields and promote grain yields by conserving more applied N in soil in rice-rapeseed rotation systems.

Nutritional and management strategies on nitrogen and phosphorus use efficiency of lactating dairy cattle on commercial farms: an environmental perspective

Dairy farm activities contribute to environmental pollution through the surplus N and P that they produce. Optimization of animal feeding and management has been described as a key strategy for decreasing N and P excretion in manure. Sixty-four commercial dairy farms were studied to assess the efficiency of N and P use in lactating herds and to identify dietary and management factors that may contribute to improving the efficiency of nutrient use for milk production, and decrease N and P excretion. The average ration was formulated to 50:50 forage:concentrate ratio with grass silage and corn silage as the main forage sources. Mean N and P intakes were 562 g/d [16.4% crude protein (CP)] and 84.8 g/d (0.40% P), respectively. Milk yield averaged 29.7 kg/d and contributed to 25.8% (standard deviation +/- 2.9) of N utilization efficiency (NUE) and 31.9% (standard deviation +/- 4.5) of P utilization efficiency (PUE). Dietary N manipulation through fitting the intake of CP to animal requirements showed a better response in terms of decreasing N excretion (R(2) = 0.70) than that estimated for P nutrition and excretion (R(2) = 0.30). Improvement in NUE helped increase PUE, despite the widespread use of feedstuffs with a high P content. Management strategies for lactating herds, such as the use of different feeding groups, periodical ration reformulation, and selection of feeding system did not show any consistent response in terms of improved NUE and PUE. The optimization of NUE and PUE contributed to decreasing the N and P excretion per unit of milk produced, and therefore, reductions in N and P excretion of between 17 and 35%, respectively, were estimated. Nevertheless, nutritional and herd management strategies were limited when N and P excretion were considered in relation to the whole lactating herd and farmland availability. Dietary CP manipulation was estimated to decrease herd N excretion by 11% per hectare, whereas dietary P manipulation would be decreased by no more than 17%. We conclude that the correct match between the ingested and required N and P, together with an increase in milk productivity, may be feasible strategies for decreasing N and P excretion by lactating herds on commercial farms.

Effect of N-(n-butyl) thiophosphoric triamide and 3,4 dimethylpyrazole phosphate on gaseous emissions from grasslands under different soil water contents

The intensification of grassland systems is leading to serious environmental risks due to the large input of nitrogen (N) in fertilizers and the subsequent gaseous losses. Addition of nitrification inhibitors (NI) or urease activity inhibitors to fertilizers could reduce these losses to the atmosphere. In the present study, the effects of the nitrification inhibitor 3,4-dimethylpyrazole phosphate (DMPP) and the urease activity inhibitor N-(n-butyl) thiophosphoric triamide (NBPT) were evaluated on NH3, N2O, NO, and CO2 emissions. Ammonium sulphate nitrate (ASN), urea and cattle slurry were applied at a rate of 70 kg N ha(-1) to a mixed clover-ryegrass sward in the Basque Country (northern Spain) under different soil water contents. NH3 and NO emissions were determined by photoacoustic and chemiluminescence respectively using an open chamber technique while N2O and CO2 emissions were measured by photoacoustic using a closed chamber technique. When the water filled pore space (WFPS) was under 60%, the application of NBPT reduced NO emissions a 34% on urea and an 18% on slurry, and the application of DMPP reduced them a 2% on ASN and a 4% on slurry. No significant effect was observed on NH3 losses. When WFPS was over 60%, no effect could be observed on NO and N2O emissions after the application of both inhibitors, but NH3 losses were reduced a 31% by NBPT when applied with the slurry. Carbon dioxide emissions were unaffected by the use of DMPP or NBPT at any soil water content. Neither grassland yield nor herbage N concentration were influenced by the application of both inhibitors.

The effect of cattle slurry electroflotation products as fertilizers on gaseous emissions and grassland yield

The climatic conditions of the Basque Country (northern Spain) provide the favorable conditions for the growth of grasslands and the development of livestock enterprises. The intensification of the farms is leading to serious environmental risks due to the great generation of manures and slurries and their subsequent inefficient management. Their application involves N losses that can be pollutant. The environmental company ADE BIOTEC S.L. is developing the process called "electroflotation" with the aim of reducing the volume of slurries from intensive livestock farms. The process consists basically of an electrolysis of the slurry catalyzed by iron which leads to the flocculation of the solid particles, giving as a final result a solid and a liquid fraction. The objective of this work was to assess the usefulness of these two fractions as fertilizers. With this aim, the environmental risk of their application was determined regarding gaseous emissions to the atmosphere (i.e., of NO, NH(3), N(2)O, and CO(2)) and their fertilizer capacity was investigated by determining their effects on grassland yield and N uptake in comparison to the untreated slurry. The untreated slurry and the solid and the liquid fractions were all applied at a rate of 70 kg NH(4)(+)-N ha(-1). The application of the products of electroflotation did not affect N(2)O and CO(2) losses, being of the same magnitude as those caused by the application of the original slurry. However, after their application, a reduction in NH(3) volatilization losses was induced in the short term and a reduction in NO losses was caused in the long term. The solid and liquid fractions both increased biomass yield with respect to the untreated slurry. The solid fraction even induced a higher N uptake than the liquid fraction and the untreated slurry.

Effects of a new nitrification inhibitor 3,4-dimethylpyrazole phosphate (DMPP) on nitrate and potassium leaching in two soils

In this study, soil column was used to study the new nitrification inhibitor 3,4-dimethylpyrazole phosphate (DMPP) on nitrate (NO3(-)-N) and potassium (K) leaching in the sandy loam soil and clay loam soil. The results showed that DMPP with ammonium sulphate nitrate (ASN) ((NH4)2SO4 and NH4NO3) or urea could reduce NO3(-)-N leaching significantly, whereas ammonium (NH4(+)-N) leaching increased slightly. In case of total N (NO3(-)-N+NH4(+)-N), losses by leaching during the experimental period (40 d) were 37.93 mg (urea), 31.61 mg (urea+DMPP), 108.10 mg (ASN), 60.70 mg (ASN+DMPP) in the sandy loam soil, and 30.54 mg (urea), 21.05 mg (urea+DMPP), 37.86 mg (ASN), 31.09 mg (ASN+DMPP) in the clay loam soil, respectively. DMPP-amended soil led to the maintenance of relatively high levels of NH4(+)-N and low levels of NO3(-)-N in soil, and nitrification was slower. DMPP supplementation also resulted in less potassium leached, but the difference was not significant except the treatment of ASN and ASN+DMPP in the sandy loam soil. Above results indicate that DMPP is a good nitrification inhibitor, the efficiency of DMPP seems better in the sandy loam soil than in the clay loam soil and lasts longer.