Use Of DMPP Research Articles

Nitrous oxide emissions and N-cycling gene abundances in a drip-fertigated (surface versus subsurface) maize crop with different N sources

Surface drip fertigation has demonstrated promising results regarding the mitigation of nitrous oxide (N2O) emissions. The use of subsurface irrigation may offer the possibility of reducing these emissions further due to the modification of the soil moisture profile and N allocation, both of which affect the biochemical processes leading to N2O fluxes. However, the mitigation potential of subsurface irrigation combined with different mineral nitrogen (N) fertilizers (ammonium or nitrate-based, use of nitrification inhibitors) still needs to be evaluated. To respond to this need, a 2-year field experiment was set up in central Spain to test two different drip-fertigation systems (surface and subsurface at 30 cm depth) and four N fertilization treatments (control, calcium nitrate, and ammonium sulfate with or without the nitrification inhibitor 3,4-dimethylpyrazole phosphate, DMPP) in an irrigated maize (Zea mays L.) crop. Nitrous oxide emissions, mineral N concentrations (ammonium, NH4+, and nitrate, NO3−), and abundance of key N genes involved in nitrification and denitrification processes were measured in two soil layers (0–20 and 20–40 cm). Regardless of the irrigation system, ammonium sulfate gave the highest cumulative N2O losses in both campaigns, while calcium nitrate and the use of DMPP were the most effective strategies to abate N2O fluxes in the first and second years, respectively. Differences between irrigation systems were not statistically significant for cumulative N2O emissions, despite the clear effect on topsoil mineral N (higher NH4+ and NO3− concentrations in surface and subsurface drip, respectively). Nitrous oxide emissions were positively correlated with soil NH4+ concentrations. Gene abundances were not a trustworthy predictor of N2O losses in the 1st year, although a clear inhibitory effect of fertilization on microbial communities (i.e., ammonia oxidizers, nitrite reducers, and N2O reducers) was observed during this campaign. During the second year, nitrifying and denitrifying genes were affected by irrigation (with higher abundances in the 20–40 cm layer in subsurface than in surface drip) and by the addition of DMPP (which had a detrimental effect on gene abundances in both irrigation systems that disappeared after the fertigation period). In conclusion, the use of DMPP or calcium nitrate instead of ammonium sulfate may enhance the chances for an additional mitigation in both surface and subsurface irrigation systems.

3,4-Dimethylpyrazole Phosphate Applied on Ammonium Sulfate Nitrate and Urea Reduces the Nitrification Process in Three Tropical Soils: An Incubation Study

ABSTRACT Objectives Nitrification inhibitors applied to soil can reduce nitrogen (N) fertilizer losses by delaying the nitrification process and reducing nitrate losses to environment with enhanced N-fertilizer management. In this study, laboratory-scale experiments were carried out in order to evaluate the efficiency of nitrification inhibitor 3,4-dimethylpyrazole phosphate (DMPP) applied on urea and ammonium sulfate nitrate (ASN) sources under three tropical soils (Typic Quartzipsamment, Typic Hapludox and Rhodic Hapludox – contrasting soil textures). Methods Soil samples were incubated over 60 days and the content of nitrate (N-NO3 −), ammonium (N-NH4 +) and pH variations were assessed periodically. In addition, N-NO3 − and N-NH4 + percentage and nitrification inhibition were assessed. Results 3,4-Dimethylpyrazole phosphate application delays the nitrification process across all three tropical soil types, being more evident in the sandy-textured soils (Typic Quartzipsamment > Typic Hapludox > Rhodic Hapludox). DMPP application reduced the N-NO3 − and N-NH4 + percentage in both ASN and urea sources, mainly between 15 and 30 (ASN) and between 7 and 30 days after N fertilization (urea). However, 45 days after N fertilization, inhibition of the nitrification process by DMPP is unlikely, regardless of N source. Conclusions The nitrification process tended to be more intense when conventional urea was applied compared to conventional ASN. Therefore, the use of DMPP would benefit more urea than ASN mainly in sandy-textured soils, where the nitrification was observed to be increased.

Strategies for mitigating N2O and N2 emissions from an intensive sugarcane cropping system

In sugarcane cropping systems, high rates of N fertiliser are typically applied as sub-surface bands creating localised zones of high mineral N concentrations. This in combination with high levels of crop residue (trash) retention and a warm and humid climate creates conditions that are known to promote soil denitrification, resulting in high emissions of the potent greenhouse gas N2O. These losses illustrate inefficient use of N fertilisers but total denitrification losses in the form of N2 and N2O remain largely unknown. We used the 15N gas flux method to investigate the effect of cane trash removal and the use of the nitrification inhibitor 3,4-dimethylpyrazole phosphate (DMPP) on N2 and N2O emissions on a commercial sugarcane farm at Bundaberg, Australia. High gaseous N losses were observed under the standard grower practice where cane trash retention and N fertiliser application (145 kg N ha−1 as urea) resulted in N2 and N2O emissions (36.1 kg N ha−1) from the subsurface N fertiliser band, with more than 50% of these losses emitted as N2O. Cane trash removal reduced N2 emission by 34% and N2O emission by 51%, but had no effect on the N2O/(N2 + N2O) ratio. The use of DMPP lowered N2 and N2O emission by 35% and 98%, respectively, reducing the percentage of these losses (N2 + N2O) emitted as N2O to only 4%. We conclude that the use of DMPP is an effective strategy to reduce N losses, minimise N2O emissions, while keeping the benefits of cane trash retention in sugarcane cropping systems.

Investigation of Soil Microbial Communities Involved in N Cycling as Affected by the Long-Term Use of the N Stabilizers DMPP and NBPT

Both, 3,4-dimethylpyrazole phosphate (DMPP) and N-(n-butyl) thiophosphoric triamide (NBPT) are commonly used as nitrogen (N) stabilizers, and are often used in agriculture to reduce nitrogen (N) loss from soils by inhibiting soil nitrification and by slowing down urea hydrolysis, respectively. The current knowledge gap concerns how soil microbial communities involved in N cycling are affected by the long-term use of DMPP and NBPT. The present field study explored the inter-annual variation of nitrous oxide (N2O) emissions and the responses of ammonia oxidizers (AOA, AOB encoded by the amoA gene), nitrite-oxidizing bacteria (NOB, encoded by the nxrA and nxrB genes), and denitrifier (encoded by the narG and nosZ genes) populations following a long-term (8 years) addition of DMPP and NBPT. The results showed that the reduction in N2O emissions by DMPP and NBPT increased year on year. The AOB population diversity significantly increased (p < 0.05) after a long-term urea application but decreased after DMPP addition. The long-term application of urea increased the potential nitrification rate (PNR) by the enrichment of the genera with a high ammonia oxidation capacity in the AOB population. In contrast, DMPP addition weakened this effect and formed a population with a low ammonia oxidation capacity. Variations in the NOB population were mainly associated with fertilizer-induced changes in substrate NO2−, whereas DMPP and NBPT had minor impacts on the NOB population. Additionally, the change in the denitrification population was indirectly affected by the soil ammonium (NH4+) content with a long-term N stabilizer application. These findings provide a new interpretation related to the response mechanisms of the nitrifier and denitrifier populations for the long-term use of N stabilizers in soils.

Evaluation of a crop rotation with biological inhibition potential to avoid N2O emissions in comparison with synthetic nitrification inhibition

Agriculture has increased the release of reactive nitrogen to the environment due to crops' low nitrogen-use efficiency (NUE) after the application of nitrogen-fertilisers. Practices like the use of stabilized-fertilisers with nitrification inhibitors such as DMPP (3,4-dimethylpyrazole phosphate) have been adopted to reduce nitrogen losses. Otherwise, cover crops can be used in crop-rotation-strategies to reduce soil nitrogen pollution and benefit the following culture. Sorghum (Sorghum bicolor) could be a good candidate as it is drought tolerant and its culture can reduce nitrogen losses derived from nitrification because it exudates biological nitrification inhibitors (BNIs). This work aimed to evaluate the effect of fallow-wheat and sorghum cover crop-wheat rotations on N2O emissions and the grain yield of winter wheat crop. In addition, the suitability of DMPP addition was also analyzed. The use of sorghum as a cover crop might not be a suitable option to mitigate nitrogen losses in the subsequent crop. Although sorghum–wheat rotation was able to reduce 22% the abundance of amoA, it presented an increment of 77% in cumulative N2O emissions compared to fallow–wheat rotation, which was probably related to a greater abundance of heterotrophic-denitrification genes. On the other hand, the application of DMPP avoided the growth of ammonia-oxidizing bacteria and maintained the N2O emissions at the levels of unfertilized-soils in both rotations. As a conclusion, the use of DMPP would be recommendable regardless of the rotation since it maintains NH4+ in the soil for longer and mitigates the impact of the crop residues on nitrogen soil dynamics.

Opportunities to improve nitrogen use efficiency in an intensive vegetable system without compromising yield

Intensive vegetable cropping systems rely heavily on nitrogen (N) inputs from multiple synthetic and organic fertilizer applications. The majority of applied N is lost to the environment through numerous pathways, including as nitrous oxide (N2 O). A field trial was conducted to examine the opportunities to reduce N input in an intensive vegetable system without compromising yield. Treatments applied were control (no N), manure (M, 408kg N ha-1 from chicken manure), grower practice (GP, 408kg N ha-1 from chicken manure + 195kg N ha-1 from fertilizer), and 2/3 GP (two-thirds of the total N input in GP), all with and without 3,4-dimethylpyrazole phosphate (DMPP). Nitrogen recovery in the GP treatment was determined using 15 N-labeled fertilizer. Using only manure significantly lowered celery (Apium graveolens L.) yield and apparent N use efficiency (ANUE) compared with GP. Reducing N input by one-third did not affect yield or ANUE. Use of DMPP increased ANUE despite no yield improvement. More than 50% of the applied N in the GP treatment was lost to the environment, with almost 10kg N ha-1 emitted as N2 O over the season, which was 67 times more than from the control. Reducing the N input by one-third or using manure only reduced N2 O emissions by more than 70% relative to GP. This study shows that there is a clear opportunity to reduce N input and N2 O emissions in high-fertilizer-input vegetable systems without compromising vegetable yield.

Can Nitrogen Source and Nitrification Inhibitors Affect In-Season Nitrogen Supply?

ABSTRACT This study sought to identify whether piggery effluent-derived nitrogen sources can be formulated with urea and nitrification inhibitors to better synchronize nitrogen (N) supply with crop demand than conventional urea fertilizer alone. A 288 pot pasture growth and leaching growth accelerator trial (5 pasture cuts) was completed with a factorial treatment structure of three N sources (2.63 g N [kg soil]−1 applied as 100% urea-N, 8% struvite-N + 92% urea-N, and 8% piggery pond sludge-N + 92% urea-N), five rates of three nitrification inhibitors (including 3,4-Dimethylpyrazole phosphate, DMPP; limonene+ethanol; and dicyandiamide, DCD), and matrix encapsulated forms of these inhibitors. Applying a combination of piggery sludge with urea increased N uptake during the first 4 weeks of plant growth (by 65%), though total N uptake throughout the trial (22 weeks) did not differ across the N-sources. The microbial community of the soil to which the sludge was added was significantly different from the un-amended soil at the conclusion of the trial. All inhibitor formulations significantly decreased leaching losses of mineral-N relative to the control (by 14 to 61%). The use of DMPP decreased initial nutrient uptake, deferring uptake until later in the experiment. Inhibitor addition resulted in microbial community effects that persisted throughout the trial. The study demonstrated that a piggery-derived N-source and a nitrification inhibitor can be used to manipulate plant N uptake to occur later or earlier in a growing period with equal cumulative uptake, achieving an 11% increase in residual N store, and decreased N leaching losses.

Effect of the nitrification inhibitor DMPP on nitrous oxide emissions and the stabilization of ammonium following the injection of dairy slurry and digestate in a soil‐column experiment

AbstractInjection of slurry or digestate below maize seeds is a relatively new technique developed to improve nitrogen use efficiency. However, this practice has the major drawback of increasing nitrous oxide (N2O) emissions. The application of a nitrification inhibitor (NI) is an effective method to reduce these emissions. To evaluate the effect of the NI 3,4‐dimethypyrazole phosphate (DMPP) on N2O emissions and the stabilization of ammonium, a two‐factorial soil‐column experiment was conducted. PVC pipes (20 cm diameter and 30 cm length) were used as incubation vessels for the soil‐columns. The trial consisted of four treatments in a randomized block design with four replications: slurry injection, slurry injection + DMPP, digestate injection, and digestate injection + DMPP. During the 47‐day incubation period, N2O fluxes were measured twice a week and cumulated by linear interpolation of the gas‐fluxes of consecutive measurement dates. After completion of the gas flux measurement, concentration of ammonium and nitrate within the soil‐columns was determined. DMPP delayed the conversion of ammonium within the manure injection zone significantly. This effect was considerably more pronounced in treatment digestate + NI than in treatment slurry + NI. Regarding the cumulated N2O emissions, no difference between slurry and digestate treatments was determined. DMPP reduced the release of N2O significantly. Transferring the results into practice, the use of DMPP is a promising way to reduce greenhouse gas emissions and nitrate leaching, following the injection of slurry or digestate.

Effects of repeated applications of urea with DMPP on ammonia oxidizers, denitrifiers, and non-targeted microbial communities of an agricultural soil in Queensland, Australia

Nitrification inhibitors have been reported to reduce nitrous oxide emission and nitrate leaching in agricultural systems. The effects of repeated applications of urea alone or in combination with nitrification inhibitors on nitrogen (N) cycling microbes involved in nitrification and denitrification together with non-targeted microbes are not well understood. Therefore, the objective of this study was to investigate the effects of repeated application of urea and DMPP on soil physio-chemistry, ammonia oxidizers and total bacteria in the soil. We collected soil samples from a 4.5-year field experiment under crop rotation with repeated application of seven treatments, namely control (CK), Urea (U), Urea + DMPP (UE) applied at 40, 80 and 120 kg N ha−1, each treatment with three replicates. Ammonia-oxidizing bacteria (AOB) gene copy numbers increased as the N application rate increased (from 0 to 120 kg N ha−1). The use of DMPP significantly reduced AOB and nirK gene copy numbers compared to urea alone at an application rate of 120 kg N ha−1. There was no treatment effect on the abundance of ammonia-oxidizing archaea (AOA), Comammox clade A and B, nosZ and bacterial 16S rRNA genes. The community composition of AOB and AOA changed with N addition and use of DMPP but increasing N addition rate changed the composition of AOB only. Addition of N increased potential nitrification rates at 80 and 120 kg N ha−1. There was no significant treatment effect on the relative abundance of bacteria at the phylum level. This experiment demonstrated that the application of N (with or without DMPP) at rates lower than 120 kg N ha−1 would not result in significant impacts on soil archaeal and bacterial ecology.

Nitrogen use efficiency of 15N urea applied to wheat based on fertiliser timing and use of inhibitors

Improving fertiliser nitrogen (N) use efficiency is essential to increase productivity and avoid environmental damage. Using a 15N mass balance approach, we investigated the effects of five N fertiliser management strategies to test the hypothesis that increasing uptake of applied N by wheat improves productivity and reduces loss of N in a semi-arid environment. Three experiments were conducted between 2012 and 2014. Treatments included urea application (50 kg N/ha) at sowing with and without nitrification inhibitor (3,4-dimethylpyrazole phosphate, DMPP) and surface broadcast with and without urease inhibitor (n-butyl thiophosphoric triamide, NBPT) at the end of tillering plus an unfertilised control. It was found that deferring fertiliser application until the end of tillering decreased losses of fertiliser N (35–52%) through increasing uptake by the crop and or recovery in the soil at harvest, while maintaining yield except when rainfall following application was low. In this case, deferring application reduced fertiliser uptake (− 71%) and grain yield (− 18%) and increased recovery of N in the soil (+ 121%). Use of DMPP or NBPT reduced N loss where seasonal conditions were conducive to denitrification during winter (DMPP) and volatilisation or denitrification later in the season (NBPT). Their effect on grain yield was less significant; DMPP increased yield (+ 3–31%) in all years and NBPT increased yield (+ 7–11%) in 2 of 3 years compared to unamended urea. The majority of crop N uptake was supplied from soil reserves and as a result, crop recovery of applied N was not strongly related to grain yield response.

Performance of nitrification inhibitors with different nitrogen fertilizers and soil textures

AbstractNitrification inhibitors (NIs), DCD (dicyandiamide), and DMPP (3,4‐dimethylpyrazole phosphate), in combination with urea (UR) and ammonium sulfate nitrate (ASN) fertilizers were studied under contrasting soil textures (sand, loam, and clay) from cultivated soils collected in Brazil and Germany. Soil samples were incubated over 50 days and the content of ammonium ( ), nitrate ( ), and soil pH were measured periodically. Applied NIs delayed the nitrification process across all soil textures. Correlation analysis indicated that combining ASN with NIs resulted in higher content and efficiency in delaying the nitrification process with high N‐conversion rate (r = –0.82). The combination of ASN+ DMPP increased the efficiency of the N‐conversion rate (r = –0.86) due to H+ release in soil, while UR+DCD (r = –0.50) had an efficiency of the N‐conversion rate similar to UR (r = –0.42). All the NIs had a better performance in reducing formation in sandy soils as compared to the loam and clay textured soils. Use of DMPP with an N fertilizer results in a soil pH decrease and can be an option to increase the efficiency of the N‐conversion rate, reducing N losses in soil. Overall, our results suggest that NIs have a better performance in reducing formation in sandy soils as compared to that of the loam and clay textured soils. Use of DMPP with ASN results in a soil pH decrease and can be an option to reduce N losses in soil.

N2O emissions from a loamy soil cropped with winter wheat as affected by N-fertilizer amount and nitrification inhibitor

Nitrogen (N) fertilization leads to the release of reactive N species, which can be detrimental to the environment. Nitrification inhibitors (NIs) are substances capable of retarding the oxidation of ammonium to nitrate, which can increase N use efficiency of applied N fertilizer and decrease N losses such as the release of the greenhouse gas nitrous oxide (N2O). Adaption of N fertilizer amount to plant demand might also decrease N surpluses and thus lower N2O emissions. We investigated the effects of N fertilizer amount (0, 120, 180, and 240 kg N ha−1 a−1) and the use of the NI 3,4-dimethylpyrazol phosphate, DMPP, on annual N2O emission from a soil cropped with winter wheat in a 2 year field experiment. N2O fluxes were affected by N level and by use of DMPP with higher fluxes under high N amounts and treatments without NI. Application of DMPP led to a reduction of annual emissions by 45%. Interestingly, also winter emissions (8–12 months after N fertilization) were decreased by DMPP. In this period, a complete degradation of DMPP was assumed. The reason for this effect remains unclear. Wheat yield and quality were unaffected by DMPP, whereas grain yield was increased with N fertilizer amount in the first year. Nevertheless, response curves of grain yield-related N2O emissions over all data showed lower optimal N fertilizer doses when DMPP was used. Application of DMPP at suboptimal N rates could help to achieve a better profitability with simultaneous reduction of the product scaled emission.

Advanced Processing of Food Waste Based Digestate for Mitigating Nitrogen Losses in a Winter Wheat Crop

The anaerobic digestion of food waste converts waste products into ‘green’ energy. Additionally, the secondary product from this process is a nutrient-rich digestate, which could provide a viable alternative to synthetically-produced fertilisers. However, like fertilisers, digestate applied to agricultural land can be susceptible to both ammonia (NH3) and nitrous oxide (N2O) losses, having negative environmental impacts, and reducing the amount of N available for crop uptake. Our main aim was to assess potential methods for mitigating N losses from digestate applied to a winter wheat crop and subsequent impact on yield. Plot trials experiments were conducted at two UK sites, England (North Wyke-NW) and Wales (Henfaes-HF), to assess NH3 and N2O losses, yield and N offtake following a single band-spread digestate application. Treatments examined were digestate (D), acidified-digestate (AD), digestate with the nitrification inhibitor DMPP (D+NI), AD with DMPP (AD+NI), and a zero-N control (C). Determination of N losses was conducted using wind tunnels for NH3, and static manual and automatic chambers for N2O. The N offtake in both grain and straw was also measured. Ammonium nitrate (NH4NO3) fertiliser N response plots (from 75 to 300 kg N ha−1) were included to compare yields with the organic N source. Across both sites, cCumulative NH3-N losses were 27.6 % from D and D+NI plots and 1.5 % for AD and AD+NI of the total N applied, a significant reduction of 95 % with acidification. Cumulative N2O losses, varied between 0.13 and 0.35 % of the total N applied and were reduced by 50 % with the use of DMPP although the differences were not significant. Grain yields for the digestate treatments were 7.52 – 9.21 and 7.23 – 9.23 t DM ha−1 at HF and NW, respectively. Yields were greater from the plots receiving acidified-digestate relative to the non-acidified treatments but the differences were not significant. The yields (as a function of the N applied with each treatment) obtained for the digestate treatments ranged between 84.2 % (D+NI) and 103.6 % (D) of the yields produced by the same N rate from an inorganic source at HF. Advanced processing of digestate

Does 3,4-dimethylpyrazole phosphate or N-(n-butyl) thiophosphoric triamide reduce nitrous oxide emissions from a rain-fed cropping system?

Nitrification and urease inhibitors have been used to reduce nitrous oxide (N2O) emissions and increase nitrogen use efficiency in many agricultural systems. However, their agronomic benefits, such as the improvement of grain yield, is uncertain. A two-year field experiment was conducted to (1) investigate whether the use of 3,4-dimethylpyrazole phosphate (DMPP) or N-(n-butyl) thiophosphoric triamide (NBPT) can reduce N2O emissions and increase grain yield and (2) explore the financial benefit of using DMPP or NBPT in a rain-fed cropping system in south-eastern Australia. The experiment was conducted at Wagga Wagga, New South Wales, Australia with wheat (Triticum aestivum L.) in 2012 and canola (Brassica napus L.) in 2013. Results showed that urea coated with DMPP reduced the cumulative N2O emission by 34% for a wheat crop in 2012 (P < 0.05) and by 62% for a canola crop in 2013 (P < 0.05) compared with normal urea, but urea coated NBPT had no effect on N2O emission for the wheat crop in 2012. Neither nitrification nor urease inhibitors increased crop yields because the low rainfall experienced led to little potential for gross N loss through denitrification, leaching or volatilisation pathways. In such dry years, only government or other financial incentives for N2O mitigation would make the use of DMPP with applied N economically viable.

Soil water content modulates the effect of the nitrification inhibitor 3,4-dimethylpyrazole phosphate (DMPP) on nitrifying and denitrifying bacteria

In the last decades, intensive agriculture management and the application of nitrogen fertilizer have led to high nitrogen losses to the environment. Among these losses is the soil emission of the potent greenhouse gas nitrous oxide (N2O) which is mainly produced by the soil microbial processes of nitrification and denitrification. The use of nitrification inhibitors with ammonium based fertilizers can be an efficient mitigation strategy to decrease these nitrogen losses. Soil water content and temperature are major factors controlling N2O production and, so, also the efficiency of the nitrification inhibitor 3,4-dimethylpyrazole phosphate (DMPP) to reduce these emissions. In this work we study the effect of soil water content and temperature on the abundance of soil bacteria, ammonia-oxidizing bacteria and denitrifying bacteria, and on the performance of DMPP modulating these different bacterial populations responsible for N2O production/consumption. The effect of DMPP on the abundance of the different bacterial populations was dependent on soil water content. Under 40% of soil water filled pore space (WFPS), the application of DMPP caused an expected decrease of the target amoA gene abundance while narG, nirK and nosZ gene abundances also decreased probably due to an indirect effect induced by the lack of substrate for denitrifiers. Under 80% of WFPS, while the application of DMPP did not induce any change in the amoA gene abundance, an unexpected increase in non-target denitrifying gene abundances (narG, nirK and nosZ) was observed at either 10°C or 20°C incubation temperatures. This finding opens a new gate of research in the use of DMPP, where nitrous oxide reductase enzyme gene (nosZ) abundance and expression should be studied in the future in order to better understand the performance of DMPP not only inhibiting nitrification, but also affecting the non-target denitrification process.

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.

Interaction of Different Wheat Genotypes and Nitrification Inhibitor 3,4-Dimethylpyrazole Phosphate Using 15N Isotope Tracing Techniques

ABSTRACTTo investigate the effect of applying 15N-labeled ammonium sulfate with or without a nitrification inhibitor 3,4-dimethylpyrazole phosphate (DMPP) on fertilizer use efficiency and crop productivity of different wheat genotypes, a field trial was conducted at the Nuclear Agricultural Department’s farm of Iran in 2013–2014. The treatments included five wheat genotypes with different 13 C isotope discrimination and three fertilizer treatments, an unfertilized control, 15N-labeled ammonium sulfate, and 15N-labeled ammonium sulfate with DMPP in three replications. Soil samples were taken after 2, 4, and 6 weeks after sowing and also at harvest time. Results from 15N experiment showed that DMPP delayed nitrification of ammonium for 42 days. Genotypes with lower discrimination index had greater uptake of ammonium ions which led to increase crop yield and nitrogen fertilizer use efficiency. The results also suggested that the use of DMPP may not be beneficial in some fast growing wheat genotypes.

Benchmarking and mitigation of nitrous oxide emissions from manures and fertilisers used in temperate vegetable crops in Australia

This study benchmarked N2O and CO2 emissions in heavily (>1 Nitrogen t annually) manured and fertilised sandy soils in temperate Australia and demonstrated the mitigation of N2O emissions using the nitrification inhibitor (NI) 3,4-dimethylpyrazole phosphate (DMPP). Three field trials conducted on celery crops from 2014 to 2016 showed that the traditional practice of adding composted chicken manure (4.5–8.0 t ha–1) to the surface of sandy soils produced large spikes in daily emissions of N2O (up to 1860 g ha–1 day–1) and that further spikes occurred with each subsequent fertiliser application. Pre-crop incorporation of manure (8–9 t ha–1) rather than surface application reduced the daily N2O-N emission flux from 1800 to <200 g ha–1 day–1. The use of DMPP, applied to both manures and fertilisers, reduced cumulative N2O emissions during the cropping period by 64–76%, with greater reductions occurring for surface-applied manures and fertilisers. DMPP-treated plots had higher levels of ammonium-N in soil. CO2 emissions were not affected by DMPP, indicating no negative effect on microbial activity. There was no difference in yields or product quality between the standard grower practice plots and plots treated with DMPP at the full or half rate, indicating overuse of N inputs and no negative effects of DMPP. Because N2O emissions were markedly reduced and yields unaffected by lower rates of NI-treated inputs, the use of NIs, particularly with manures, is an excellent cropping practice for these sandy soils to reduce the negative effect of excess N on the environment and to avoid the overuse of fertilisers and manures by growers. This study showed that the cumulative emissions of N2O for celery production over the cropping period using the standard grower practice translated to annual emissions of 27–68 kg N ha–1 year–1, among the highest recorded for Australian crops.

Effect of the nitrification inhibitor (DMPP) on soil nitrous oxide emissions and yield in a lettuce crop in Queensland, Australia

The use of nitrification inhibitors, in combination with ammonium based fertilisers, has been promoted recently as an effective method to reduce nitrous oxide (N2O) emissions from fertilised agricultural fields, whilst increasing yield and nitrogen use efficiency. However, to date no data is available on the use of nitrification inhibitors in sub-tropical vegetable systems. A field experiment investigated the effect of the nitrification inhibitor 3,4-dimethylpyrazole phosphate (DMPP) on N2O emissions and yield from lettuce production in sub-tropical Australia. Soil N2O fluxes were monitored continuously over 120 days with a fully automated system. Measurements were taken from three subplots for each treatment within a randomized complete blocks design. Cumulative N2O emissions over the 120 day observation period amounted to 191, 93 and 46 g-N ha-1 in the conventional fertiliser (CONV), the DMPP treatment and the zero fertiliser (0N) respectively. Consequently, the use of DMPP decreased seasonal N2O emissions by more than 50%, but had no significant impact on lettuce yield. The temporal variation of N2O fluxes showed only low emissions over the lettuce cropping period in all treatments, but significantly elevated emissions were observed in the CONV fertilized and DMPP treatment postharvest, following lettuce residues being incorporated into the soil. This study highlights that DMPP can substantially reduce N2O emissions from vegetable cropping systems. It also emphasizes that N input from vegetable crop residues incorporated into the soil after harvest can lead to substantially elevated N2O emission. Hence, in such systems post-harvest emissions need to be in the centre of attention for developing N2O mitigation strategies.

Agronomic responses of grain sorghum to DMPP-treated urea on contrasting soil types in north-eastern Australia

Grain sorghum grown in north-eastern Australia’s cropping region increasingly requires nitrogen (N) fertiliser to supplement the soil available N supply. The rates of N required can be high when fallows between crop seasons are short (higher cropping intensities) and when yield potentials are high. Fertiliser N is typically applied before or at crop sowing and is vulnerable to environmental loss in the period between application and significant crop N demand due to potentially intense rainfall events in the summer-dominant rainfall environment. Nitrification inhibitors added to urea can reduce certain gaseous loss pathways but the agronomic efficacy of these products has not been explored. Urea and urea coated with the nitrification inhibitor DMPP (3,4-dimethylpyrazole phosphate) were compared in sorghum crops grown at five research sites over consecutive summer sorghum growing seasons in south-east Queensland. Products were compared in terms of crop responses in dry matter, N uptake and grain yield, with DMPP found to produce only subtle increases on grain yield. There was no effect on dry matter or N uptake. Outcomes suggest any advantages from use of DMPP in this region are most significant in situations where higher fertiliser application rates (>80kgN/ha) are required.