Use Of Nitrification Inhibitors Research Articles

Greenhouse gas emissions from a wheat–maize double cropping system with different nitrogen fertilization regimes

Here, we report on a two-years field experiment aimed at the quantification of the emissions of nitrous oxide (N2O) and methane (CH4) from the dominant wheat–maize double cropping system in North China Plain. The experiment had 6 different fertilization strategies, including a control treatment, recommended fertilization, with and without straw and manure applications, and nitrification inhibitor and slow release urea. Application of N fertilizer slightly decreased CH4 uptake by soil. Direct N2O emissions derived from recommended urea application was 0.39% of the annual urea-N input. Both straw and manure had relatively low N2O emissions factors. Slow release urea had a relatively high emission factor. Addition of nitrification inhibitor reduced N2O emission by 55%. We conclude that use of nitrification inhibitors is a promising strategy for N2O mitigation for the intensive wheat–maize double cropping systems.

Nitrous oxide and greenhouse gas emissions from grazed pastures as affected by use of nitrification inhibitor and restricted grazing regime

Integration of a restricted grazing regime in winter with the use of a nitrification inhibitor can potentially reduce N2O emissions from grazed pasture systems. A three year field study was conducted to compare annual N2O emission rates from a “tight nitrogen” grazed farmlet with those from a control farmlet. The control farmlet was managed under a conventional rotational all-year grazing regime, while the “tight nitrogen” farmlet was under a similar grazing regime, except during winter and early spring seasons when cows grazed for about 6h per day. A nitrification inhibitor (dicyandiamide, DCD) was applied onto the “tight nitrogen” farmlet immediately after grazing through winter and early spring. A chamber technique was used to measure N2O emissions in several paddocks from each farmlet during three contrasting seasons each year. The IPCC (Intergovernmental Panel on Climate Change) inventory methodology was used to estimate CH4 and indirect N2O emissions and the life cycle assessment (LCA) methodology was used to calculate CO2 emissions from the farm systems. The individual and combined effects of restricted grazing and DCD use on N2O emissions were also determined. During the late spring/summer and autumn periods, N2O emission rates were generally similar between the two farmlets. The use of a restricted grazing regime and DCD reduced N2O emissions from the grazed farmlet during the winter/early spring seasons by 43–55%, 64–79% and 45–60% over each of the three years, respectively. The use of restricted grazing and DCD both resulted in a similar reduction in N2O emissions, but there was no significant further reduction from the combination of these technologies. For the three study years, the annual N2O emission rate from the “tight nitrogen” farmlet was 20% lower, on average, than from the control. Total annual greenhouse gas (GHG) emissions, however, were only 5% less in the “tight nitrogen” system.

Strategies to mitigate nitrous oxide emissions from herbivore production systems

Herbivores are a significant source of nitrous oxide (N2O) emissions. They account for a large share of manure-related N2O emissions, as well as soil-related N2O emissions through the use of grazing land, and land for feed and forage production. It is widely acknowledged that mitigation measures are necessary to avoid an increase in N2O emissions while meeting the growing global food demand. The production and emissions of N2O are closely linked to the efficiency of nitrogen (N) transfer between the major components of a livestock system, that is, animal, manure, soil and crop. Therefore, mitigation options in this paper have been structured along these N pathways. Mitigation technologies involving diet-based intervention include lowering the CP content or increasing the condensed tannin content of the diet. Animal-related mitigation options also include breeding for improved N conversion and high animal productivity. The main soil-based mitigation measures include efficient use of fertilizer and manure, including the use of nitrification inhibitors. In pasture-based systems with animal housing facilities, reducing grazing time is an effective option to reduce N2O losses. Crop-based options comprise breeding efforts for increased N-use efficiency and the use of pastures with N2-fixing clover. It is important to recognize that all N2O mitigation options affect the N and carbon cycles of livestock systems. Therefore, care should be taken that reductions in N2O emissions are not offset by unwanted increases in ammonia, methane or carbon dioxide emissions. Despite the abundant availability of mitigation options, implementation in practice is still lagging. Actual implementation will only follow after increased awareness among farmers and greenhouse gases targeted policies. So far, reductions in N2O emissions that have been achieved are mostly a positive side effect of other N-targeted policies.

Recent approaches in nitrogen management for sustainable agricultural production and eco-safety

Among plant nutrients, nitrogen (N) is the most important. Its importance as a growth- and yield-determining nutrient has led to large and rapid increases in N application rates, but often with poor use efficiency. Nitrogen management requires special attention in its use so that the large losses can be minimized and the efficiency maximized. Site-specific nutrient management (SSNM) has been found especially useful to achieve the goals of improved productivity and higher N use efficiency (NUE). Leaf color charts and chlorophyll meters assist in the prediction of crop N needs for rice and wheat, leading to greater N-fertilizer efficiency at various yield levels. Crop simulation models can be used in combination with field information and actual weather data to make recommendations to achieve higher NUE. Remote sensing tools are also used to predict crop N demands precisely. At the same time, traditional techniques like balanced fertilization, integrated N management (INM), use of nitrification inhibitors and slow-release nitrogenous fertilizers (SRNF), split application and nutrient budgeting, among others, are also used to supplement recent N management techniques to attain higher productivity and NUE, and reduce environmental pollution through the leakage of fertilizer N.

Survey of nitrogen fertilizer use on corn in Minnesota

A survey was conducted in the spring of 2010 to characterize the use of nitrogen (N) fertilizer on corn (Zea mays L.) by Minnesota farmers in the 2009 growing season. Detailed information on synthetic N fertilizer management practices was collected from interviews with 1496 farmers distributed across all of the corn growing regions in the state. The total amount of corn they grew represented 6.8% of the ha of corn harvested in Minnesota in 2009. This report summarizes data on: (1) N fertilizer rates, (2) major N sources (excluding manures), (3) application timing of the major N source, (4) use of nitrification inhibitors, additives, and specialty N fertilizer formulations, (5) fertilizer placement and incorporation practices, (6) use of starter fertilizer, split and sidedress applications, and other N sources such as ammonium phosphates, (7) N fertilization of irrigated corn, and (8) use of soil testing as a fertility management tool. Many of the survey results are reported as statewide averages, but where regional differences occurred the data are broken down and presented separately for different parts of the state. This survey provides the most comprehensive set of data on N fertilizer use on corn that has been collected in Minnesota. The information can be used to target research and education programs to improve N management for both production and environmental goals. The statewide average N fertilizer rate was 157kgNha−1. Variable rate application was used to apply N by 23% of farmers. About 59% of surveyed farmers applied the majority of their N fertilizer in the spring before planting, 32.5% made their main N application in the fall, and 9% sidedressed the majority of their N after corn emergence. Most farmers used anhydrous ammonia (46%) or urea (45%) as their major source of N fertilizer, while 6.5% used a liquid N formulation as their primary N source. Soil testing was used as a fertility management tool on 84% of the surveyed fields in the last 5years. Overall results indicate that N fertilizer use by Minnesota corn farmers is generally consistent with University of Minnesota Extension N management guidelines. Fertilizer N use could probably be improved by taking adequate N credit for previous soybean crops. In the South Central region of the state, fertilizer N recovery could potentially be improved by increased use of nitrification inhibitors with fall-applied anhydrous ammonia or by delaying anhydrous ammonia application until spring.

Pasture dry matter responses to the use of a nitrification inhibitor: a national series of New Zealand farm trials

The use of nitrification inhibitors has become increasingly common on dairy farms in NZ since 2004, ostensibly to reduce nitrogen (N) loss from nitrate leaching and nitrous oxide emissions. A potential benefit of this reduction in N loss, however, is an increase in dry matter (DM) production. Pasture response data were collated from a national series of farm trials conducted in 132 paddocks on 37 farms in the North Island (NI) and South Island (SI) of New Zealand where paddocks were randomly split into two halves with one half treated with the nitrification inhibitor eco-nTM. Measurements conforming to a strict protocol were made using pasture plate meters. There was a highly significant overall DM response to inhibitor use of 19% across all trials (14% NI, 21% SI) although full-year responses were more variable between NI regions (4–27%) than SI regions (12–31%). Generally, DM responses were greater than those demonstrated by previous small-scale experimental trials and this may indicate the influence of a farm–system effect. Several reasons are speculated for this effect but further research is required to identify the factors involved.

硝化抑制剂对蔬菜土硝化和反硝化细菌的影响

Nitrogen(N) loss via nitrate(NO-3) leaching from soil is one of the major contributors to environmental degradation.Vegetable soil is characterized by intensive fertilization with low nitrogen usage efficiency as a result of NO-3 leaching.Nitrification and de-nitrification are the most important processes in NO-3 formation and transformation,and are driven by functional microorganism in soil.The use of nitrification inhibitors,such as DCD,may play a key role in mitigating N loss. Investigations were conducted on the inhibitory effect of DCD to the functional microorganisms among the processes of nitrification and de-nitrification,and the relationship between DCD and nitrogen transformation.In this research,two kinds of vegetable soils were selected from Huangxing country,Changsha,reflecting long-term(about 20 years) and short-term vegetable cropping(1 year).Each sample was a mixture of 5 cores(0—20cm top soil) randomly taken in the same field.Two treatments for each soil sample were conducted: CK treatment(urea at 0.2g N/kg),and DCD treatment(urea at 0.2g N/kg with DCD 0.02g/g),each treatment with 3 replicates.The pots were incubated for 64 days at 25℃,and systematically measured NH+4 and NO-3 concentrations.According to the dynamics of NH+4 transformation,three soil samples were taken at the 3rd,7th and 64th days,which represented the increasing,peak and decreasing status of NH+4 concentration.The abundances of nitrifying gene amoA and denitrifying gene nirK were analyzed by Real-time PCR,. Results indicated that NH+4 concentrations of DCD treatments increased 248% and 225% compared to the CK treatment in the long-term and short term vegetable soils,respectively.NO-3 concentrations of DCD treatments decreased 31% and 20% compared to the CK treatment in the long-term and short-term vegetable soils separately.Furthermore,NH+4 concentration of DCD treated short term soil decreased slightly while long term soil remained the same level,suggesting that DCD had a better effect on long-term vegetable soil.The abundances of 16S rRNA gene and nirK gene had no significant difference between two treatments.However,the amoA gene abundance of DCD treatment for the long-term vegetable soil and the short-term vegetable soil had significantly decreased compared to the CK treatment,61% and 48% respectively on the 3rd day,71% and 54% respectively on the 7th day,but no differences were observed between two treatments after 64 days incubation.There was extremely significant correlation between NO-3 concentration and the amoA gene abundance. The results showed that the process of nitrification could be inhibited by DCD through restraining the growth of nitrifying bacteria.In addition,intensive application of inorganic fertilizer accelerated N element cycle in soil through the shift of composition and abundance of nitrogen-transformation functional microorganism.Thus,it might be better to use DCD together with suitable amount of fertilizer to improve nitrogen fertilizer usage efficiency and reduce nitrate loss.

Nutrient Management Practices Used in Potato Production In Idaho

Sound nutrient-management practices are an essential component of modern intensive potato (Solanum tuberosum) production systems. Economic and environmental issues are requiring Idaho potato producers to use management practices that are effective and efficient to remain competitive in the market. Identical potato production management surveys were conducted in 1997 and again in 2006–2007 to determine current nutrient management practices used by Idaho potato growers. This Dillman mail-based survey collected data that were used to determine current nutrient-management strategies and changes that have occurred over the past 10 years. In 2006–2007, more than 77% of growers used preplant soil tests for determining nitrogen (N) application needs. More than 96% of potato growers relied on petiole analysis of potato plant tissue for N management during the growing season. Changes have occurred in only 7 of 28 nutrient-management categories evaluated in the past 10 years, indicating maturity rather than evolution in nutrient management strategies for potatoes. Over the past 10 years, application rates of N have decreased, while potassium (K) rates have increased. There has been a decrease in the number of growers who plant legumes in crop rotation as a source of N. The use of nitrification inhibitors, precision fertilizer management, and application of manure to potato fields has increased in the past 10 years. The overall lack of changes in nutrient management in the past 10 years may indicate that nutrient-management strategies for potatoes in Idaho are mature and successful.

Methanotroph abundance not affected by applications of animal urine and a nitrification inhibitor, dicyandiamide, in six grazed grassland soils

Methanotrophs are an important group of methane (CH4)-oxidizing bacteria in the soil, which act as a major sink for the greenhouse gas, CH4. In grazed grassland, one of the ecologically most sensitive areas is the animal urine patch soil, which is a major source of both nitrate (NO3 −) leaching and nitrous oxide (N2O) emissions. Nitrification inhibitors, such as dicyandiamide (DCD), have been used to mitigate NO3 − leaching and N2O emissions in grazed pastures. However, it is not clear if the high nitrogen loading rate in the animal urine patch soil and the use of nitrification inhibitors would have an impact on the abundance of methanotrophs in grazed grassland soils. The purpose of this study was to determine the effect of animal urine and DCD on methanotroph abundance in grazed grassland soils. A laboratory incubation study was conducted to determine the effect of urine and DCD applications on the abundance of methanotrophs in six grazed grassland soils sampled from across New Zealand, using real-time PCR targeting the functional pmoA gene. Results showed that the pmoA gene copy numbers were low in these soils, mostly below 2.36 × 104 g−1 soil except in the West Coast soil where pmoA gene copy number reached 8.95 × 105 g−1 soil. Most of the clones identified were aligned to the type II methanotrophs. There was no significant effect (P < 0.05) on the abundance of methanotrophs by the applications of urine at 1,000 kg N ha−1 or DCD at 10 kg ha−1. These results suggest that the abundance of methanotrophs is not affected by urine deposition or the application of DCD to mitigate NO3 − leaching and N2O emissions in grazed grassland soils.

The use of nitrification inhibitors as a strategy for increasing grass yields: can this environmental tool also benefit agronomic efficiency?

The use of nitrification inhibitors as a strategy for increasing grass yields: can this environmental tool also benefit agronomic efficiency?

Influence of Two Nitrification Inhibitors (DCD and DMPP) on Annual Ryegrass Yield and Soil Mineral N Dynamics after Incorporation with Cattle Slurry

Nitrogen (N) losses through nitrate leaching, occurring after slurry spreading, can be reduced by the use of nitrification inhibitors (NIs) such as dicyandiamide (DCD) and 3,4‐dimethyl pyrazole phosphate (DMPP). In the present work, the effects of DCD and DMPP, applied at two rates with cattle slurry, on soil mineral N profiles, annual ryegrass yield, and N uptake were compared under similar pedoclimatic conditions. Both NIs delayed the nitrate formation in soil; however, DMPP ensured that the soil mineral N was predominantly in the ammonium form rather than in the nitrate form for about 100 days, whereas with DCD such effect was observed only during the first 40 days after sowing. Furthermore, the use of NIs led to an increase of the dry‐matter (DM) yields in a range of 32–54% and of the forage N removal in a range of 34–68% relative to the slurry‐only (SO) treatment (without NIs). A DM yield of 8698 kg ha−1 was obtained with the DMPP applied at the greater rate against only 7444 kg ha−1 obtained with the greater rate of DCD (4767 kg ha−1 in the SO treatment). Therefore, it can be concluded that DMPP is more efficient as an NI than DCD when combined with cattle slurry.

A preliminary study to model the effects of a nitrification inhibitor on nitrous oxide emissions from urine-amended pasture

New Zealand's grazed pastures receive large quantities of nitrogen (N) inputs from animal excreta and chemical fertilisers. While N promotes pasture growth, surplus N can cause environmental problems by leaching into waterways or by nitrifying and denitrifying to form the greenhouse gas, nitrous oxide (N 2O). Various approaches have been attempted to mitigate the economic and environmental impacts of N losses. One such approach is the use of nitrification inhibitors (NIs). The value of these inhibitors in mitigating N losses in grazed pasture partly depends on their rate of biodegradation and persistence in soils. A simplified model of nitrification inhibition was used with the process-based NZ-DNDC model to investigate the effect of NI dicyandiamide (DCD) on transformations of N to nitrate (NO 3 −) and subsequent reduction to N 2O in a grazed pasture system receiving cow urine at application rate of 600 kg N/ha. The modelled N 2O emissions with and without DCD application were comparable to the field measurements on Tokomaru silt loam soil, assuming that the effect of the DCD was to decrease the nitrification rate by about 70%. An attempt was also made to simulate the effect of the biological degradation of DCD by exponentially decreasing the inhibitor effectiveness with time. However, this did not improve the fit of the modelled N 2O emissions over the 50-day measurement period. Further refinements including the effects of soil type, and changes in NI concentration throughout the soil profile over time and its subsequent effect on N transformations will be developed as more experimental data become available.

Global scale DAYCENT model analysis of greenhouse gas emissions and mitigation strategies for cropped soils

Conversion of native vegetation to cropland and intensification of agriculture typically result in increased greenhouse gas (GHG) emissions (mainly N 2O and CH 4) and more NO 3 leached below the root zone and into waterways. Agricultural soils are often a source but can also be a sink of CO 2. Regional and larger scale estimates of GHG emissions are usually obtained using IPCC emission factor methodology, which is associated with high uncertainty. To more realistically represent GHG emissions we used the DAYCENT biogeochemical model for non-rice major crop types (corn, wheat, soybean). IPCC methodology estimates N losses from croplands based solely on N inputs. In contrast, DAYCENT accounts for soil class, daily weather, historical vegetation cover, and land management practices such as crop type, fertilizer additions, and cultivation events. Global datasets of weather, soils, native vegetation, and cropping fractions were mapped to a 1.9° × 1.9° resolution. Non-spatial data (e.g., rates and dates of fertilizer applications) were assumed to be identical within crop types across regions. We compared model generated baseline GHG emissions and N losses for irrigated and rainfed cropping with land management alternatives intended to mitigate GHG emissions. Reduced fertilizer resulted in lower N losses, but crop yields were reduced by a similar proportion. Use of nitrification inhibitors and split fertilizer applications both led to increased (~ 6%) crop yields but the inhibitor led to a larger reduction in N losses (~ 10%). No-till cultivation, which led to C storage, combined with nitrification inhibitors, resulted in reduced GHG emissions of ~ 50% and increased crop yields of ~ 7%.

Contribution of N2O to the greenhouse gas balance of first‐generation biofuels

AbstractIn this study, we analyze the impact of fertilizer‐ and manure‐induced N2O emissions due to energy crop production on the reduction of greenhouse gas (GHG) emissions when conventional transportation fuels are replaced by first‐generation biofuels (also taking account of other GHG emissions during the entire life cycle). We calculate the nitrous oxide (N2O) emissions by applying a statistical model that uses spatial data on climate and soil. For the land use that is assumed to be replaced by energy crop production (the ‘reference land‐use system’), we explore a variety of options, the most important of which are cropland for food production, grassland, and natural vegetation. Calculations are also done in the case that emissions due to energy crop production are fully additional and thus no reference is considered. The results are combined with data on other emissions due to biofuels production that are derived from existing studies, resulting in total GHG emission reduction potentials for major biofuels compared with conventional fuels. The results show that N2O emissions can have an important impact on the overall GHG balance of biofuels, though there are large uncertainties. The most important ones are those in the statistical model and the GHG emissions not related to land use. Ethanol produced from sugar cane and sugar beet are relatively robust GHG savers: these biofuels change the GHG emissions by −103% to −60% (sugar cane) and −58% to −17% (sugar beet), compared with conventional transportation fuels and depending on the reference land‐use system that is considered. The use of diesel from palm fruit also results in a relatively constant and substantial change of the GHG emissions by −75% to −39%. For corn and wheat ethanol, the figures are −38% to 11% and −107% to 53%, respectively. Rapeseed diesel changes the GHG emissions by −81% to 72% and soybean diesel by −111% to 44%. Optimized crop management, which involves the use of state‐of‐the‐art agricultural technologies combined with an optimized fertilization regime and the use of nitrification inhibitors, can reduce N2O emissions substantially and change the GHG emissions by up to −135 percent points (pp) compared with conventional management. However, the uncertainties in the statistical N2O emission model and in the data on non‐land‐use GHG emissions due to biofuels production are large; they can change the GHG emission reduction by between −152 and 87 pp.

Climate change mitigation for agriculture: water quality benefits and costs

New Zealand is unique in that half of its national greenhouse gas (GHG) inventory derives from agriculture--predominantly as methane (CH4) and nitrous oxide (N2O), in a 2:1 ratio. The remaining GHG emissions predominantly comprise carbon dioxide (CO2) deriving from energy and industry sources. Proposed strategies to mitigate emissions of CH4 and N2O from pastoral agriculture in New Zealand are: (1) utilising extensive and riparian afforestation of pasture to achieve CO2 uptake (carbon sequestration); (2) management of nitrogen through budgeting and/or the use of nitrification inhibitors, and minimizing soil anoxia to reduce N2O emissions; and (3) utilisation of alternative waste treatment technologies to minimise emissions of CH4. These mitigation measures have associated co-benefits and co-costs (disadvantages) for rivers, streams and lakes because they affect land use, runoff loads, and receiving water and habitat quality. Extensive afforestation results in lower specific yields (exports) of nitrogen (N), phosphorus (P), suspended sediment (SS) and faecal matter and also has benefits for stream habitat quality by improving stream temperature, dissolved oxygen and pH regimes through greater shading, and the supply of woody debris and terrestrial food resources. Riparian afforestation does not achieve the same reductions in exports as extensive afforestation but can achieve reductions in concentrations of N, P, SS and faecal organisms. Extensive afforestation of pasture leads to reduced water yields and stream flows. Both afforestation measures produce intermittent disturbances to waterways during forestry operations (logging and thinning), resulting in sediment release from channel re-stabilisation and localised flooding, including formation of debris dams at culverts. Soil and fertiliser management benefits aquatic ecosystems by reducing N exports but the use of nitrification inhibitors, viz. dicyandiamide (DCD), to achieve this may under some circumstances impair wetland function to intercept and remove nitrate from drainage water, or even add to the overall N loading to waterways. DCD is water soluble and degrades rapidly in warm soil conditions. The recommended application rate of 10 kg DCD/ha corresponds to 6 kg N/ha and may be exceeded in warm climates. Of the N2O produced by agricultural systems, approximately 30% is emitted from indirect sources, which are waterways draining agriculture. It is important therefore to focus strategies for managing N inputs to agricultural systems generally to reduce inputs to wetlands and streams where these might be reduced to N2O. Waste management options include utilizing the CH4 resource produced in farm waste treatment ponds as a source of energy, with conversion to CO2 via combustion achieving a 21-fold reduction in GHG emissions. Both of these have co-benefits for waterways as a result of reduced loadings. A conceptual model derived showing the linkages between key land management practices for greenhouse gas mitigation and key waterway values and ecosystem attributes is derived to aid resource managers making decisions affecting waterways and atmospheric GHG emissions.

Influences of nitrification inhibitor 3,4-dimethyl pyrazole phosphate on nitrogen and soil salt-ion leaching

An undisturbed heavy clay soil column experiment was conducted to examine the influence of the new nitrification inhibitor, 3,4-dimethylpyrazole phosphate (DMPP), on nitrogen and soil salt-ion leaching. Regular urea was selected as the nitrogen source in the soil. The results showed that the cumulative leaching losses of soil nitrate-N under the treatment of urea with DMPP were from 57.5% to 63.3% lower than those of the treatment of urea without DMPP. The use of nitrification inhibitors as nitrate leaching retardants may be a proposal in regulations to prevent groundwater contaminant. However, there were no great difference between urea and urea with DMPP treatments on ammonium-N leaching. Moreover, the soil salt-ion leaching losses of Ca2+, Mg2+, K+, and Na+ were reduced from 26.6% to 28.8%, 21.3% to 27.8%, 33.3% to 35.5%, and 21.7% to 32.1%, respectively. So, the leaching losses of soil salt-ion were declined for nitrification inhibitor DMPP addition, being beneficial to shallow groundwater protection and growth of crop. These results indicated the possibility of ammonium or ammonium producing compounds using nitrification inhibitor DMPP to control the nitrate and nutrient cation leaching losses, minimizing the risk of nitrate pollution in shallow groundwater.

Influence of the DMPP (3,4-dimethyl pyrazole phosphate) on nitrogen transformation and leaching in multi-layer soil columns

The application of nitrogen fertilizers leads to various ecological problems such as nitrate leaching. The use of nitrification inhibitors as nitrate leaching retardants is a proposal that has been suggested for inclusion in regulations in many countries. In this study, using a multi-layer soil column device, the influence of new nitrification inhibitor DMPP (3,4-dimethyl pyrazole phosphate) was studied for understanding the nitrogen vertical transformation and lowering the nitrate leaching at different soil profile depths. The results indicated that, within 60 d of experiment, the regular urea added 1.0% DMPP can effectively inhibit the ammonium oxidation in the soil, and improve the ammonium concentration in soil solution over the 20 cm depths of soil profile, while decline the concentrations of nitrate and nitrite. No obvious difference was found on ammonium concentrations in soil solution collected from deep profile under 20 cm depths between regular urea and the urea added 1.0% DMPP. There was also no significant difference for the nitrate, ammonium and nitrite concentrations in the soil solution under 40 cm depths of soil profile with the increasing nitrogen application level, among the treatments of urea added 1.0% DMPP within 60 d. It is proposed that DMPP could be used as an effective nitrification inhibitor in some region to control ammonium oxidation and decline the ion-nitrogen leaching, minimizing the shallow groundwater pollution risk and being beneficial for the ecological environment.

The uncertain search for the diffuse silver bullet: science, policy and prospects

The overwhelming importance of diffuse sources as a determinant of receiving water quality has been recognised for over 30 years. Significant research and development on techniques for reducing inputs in the riparian zone has resulted in numerous guideline documents being produced. Yet despite this research effort, and the apparently successful transfer of key results to water resource managers, the public perception in New Zealand is that the quality of receiving waters continues to decline. In this paper we examine the veracity of that perception through examination of state-of-the-environment reporting, discussions with water resource managers, and published literature. Using a case study of Lake Taupo, New Zealand as an example, we discuss the difficulties faced by water resource managers in arresting declines in water quality. We compare the reduction in potential nutrient exports possible between 'non-invasive' mitigation techniques such as riparian buffer strips, constructed and natural wetlands and source control measures such as the use of nitrification inhibitors and wintering pads. Finally, we look at options available should voluntary measures or best management practices fail to deliver the nutrient reductions that are necessary to maintain lake water quality.

Influence of Physicochemical Parameters of Neem (Azadirachta indica A Juss) Oils on Nitrification Inhibition in Soil

The technology for the production of neem oil coated urea (NOCU) developed by the Indian Agricultural Research Institute is in the pipeline for adaption by several Indian fertilizer industries. Use of nitrification inhibitors is one of the methods of improving the nitrogen use efficiency (NUE) of nitrogenous fertilizers in agriculture. However, standard specifications for the neem oil as a raw material of NOCU are desired. Accordingly, the present study was undertaken to evaluate 25 samples of neem oils comprising 11 samples of expeller grade (EG) oils, 8 samples of cold-pressed (CP) oils, 3 samples of solvent-extracted oils, and 2 commercial formulations. NOCU was prepared using these oils (5000 ppm of urea-N). The soils fertilized with NOCUs (200 ppm of urea-N) were incubated at 27 degrees C and 50% water-holding capacity for a period of 15 days. Nitrapyrin (0.5% of N) coated urea served as the reference and prilled urea as control. Samples were analyzed for NH4+-N, NO2--N, and NO3--N using standard methods. The percent nitrification inhibition (NI) was calculated, and the results revealed that all of the neem oils caused NI ranging from 4.0 to 30.9%. Two samples of EG oils and two commercial formulations were found to be the best, causing 27.0-30.9% NI. Iodine, acid, and saponification values and meliacin content of all of the oils were analyzed and correlated with NI. The results revealed the direct influence of meliacin content of the neem oils on NI, which, however, was found to be negatively correlated with saponification and iodine values. There is, therefore, a need to introduce new Bureau of Indian Standards (BIS) specifications for neem oils as raw materials of NOCU.

Evaluation of nitrification inhibitor 3,4-dimethyl pyrazole phosphate on nitrogen leaching in undisturbed soil columns

The application of nitrogen fertilizers leads to various ecological problems such as nitrate leaching. The use of nitrification inhibitors (NI) as nitrate leaching retardants is a proposal that has been suggested for inclusion in regulations in many countries. In this study, the efficacy of the new NI, 3,4-dimethyl pyrazole phosphate (DMPP), was tested under simulated high-risk leaching situations in two types of undisturbed soil columns. The results showed that the accumulative leaching losses of soil nitrate under treatment of urea with 1.0% DMPP, from columns of silt loam soil and heavy clay soil, were 66.8% and 69.5% lower than those soil columns tested with regular urea application within the 60 days observation, respectively. However, the losses of ammonium leaching were reversely increased 9.7% and 6.7% under the former treatment than the latter one. Application of regular urea with 1.0% DMPP addition can reduce about 59.3%-63.1% of total losses of inorganic nitrogen via leaching. The application of DMPP to urea had stimulated the inhibition effects of DMPP on the ammonium nitrification process in the soil up to 60 days. It is proposed that the DMPP could be used as an effective NI to control inorganic N leaching losses, minimizing the risk of nitrate pollution in shallow groundwater.