Research on the Factors Affecting Nitrification Inhibition of Dicyandiamide(DCD) in Latosol

[Objective] This research aimed at studying the effects of application amount of DCD and physics and chemistry characteristics of soil such as temperature,moisture content,organic matter content and pH on the inhibition of nitrification when applying nitrification inhibitor DCD in latosol.[Method] The experiment was carried out under aerobic incubated conditions.[Result] A significant delay period of nitrification was observed when the application amount of DCD was 10 mg/kg soil,and the inhibition can at least last for 56 d.When the cultural temperature had increased from 10 to 30 ℃,the duration of nitrification inhibition was shortened from 90 to 30 d.The nitrification inhibition of DCD was reduced with the increasing soil moisture content,organic matter content and soil pH,while the duration of nitrification inhibition was prolonged with the decreasing soil moisture content,organic matter content and soil pH.[Conclusion] Nitrification inhibition of DCD can be improved by increasing the application amount or reducing soil temperature,moisture content,organic matter content and pH.

Dicyandiamide Sorption-Desorption Behavior on Soils and Peat Humus

The sorption-desorption behavior of dicyandiamide (DCD) is an importantchemical process that affects DCD fate and mobility in soils. Therefore, this study quantified DCDsorption-desorption on a phaeozem (Mollisol), a burozem (Alfisol), a soil with organicmatter-removed and peat humus using the batch-equilibration procedure, and identified soilproperties that influenced DCD sorption. The sorption on peat humus was higher than that on thephaeozem and the burozem, with much lower sorption observed on the soil with organic matter-removed,indicating that soil organic matter was the main carrier of DCD sorption. Due to its amphipathicproperty the DCD molecule sorption on the phaeozem and the burozem decreased as pH increased fromabout 2 to 5, but a further increase in pH led to a rise in DCD sorption. The DCD desorptionhysteretic effect for peat humus was greater than that for the phaeozem and the burozem using 0.01mol L^(-1) CaCl_2 as the background electrolyte, suggesting that the hydrophobic domains of organicmatter may play an important role in DCD sorption.

Curing Reaction Kinetics of Epoxy Resin Using Dicyandiamide Modified by Aromatic Amines

The curing reaction and reaction mechanism of epoxy resin E-44, for which aromatic amine modified dicyandiamide was used as a curing reagent, were investigated by means of differential scanning calorimetry （DSC）. The results showed that the modified dicyandiamide had better curing characteristic than unmodified dicyandiamide for epoxy resin E-44, and the curing reaction could be carried out at moderate temperature. Apparent activation energy of the curing reaction was decreased appreciably from 123.829 kJ/mol to 61.550-64.405 kJ/mol, and reaction order was decreased from 0.941 to 0.896-0.900. Curing reaction mechanism also was discussed.

Effect of phosphogypsum and dicyandiamide as additives on NH_3,N_2O and CH_4 emissions during composting

A laboratory scale experiment of composting in a forced aeration system using pig manure with cornstalks was carried out to investigate the effects of both phosphogypsum and dicyandiamide （DCD, C2 H4 N4 ） as additives on gaseous emissions and compost quality. Besides a control, there were three amended treatments with different amounts of additives. The results indicated that the phosphogypsum addition at the rate of 10% of mixture dry weight decreased NH3 and CH4 emissions significantly during composting. The addition of DCD at the rate of 0.2% of mixture dry weight together with 10% of phosphogypsum further reduced the N20 emission by affecting the nitrification process. Reducing the phosphogypsum addition to 5% in the presence of 0.2% DCD moderately increased the NH3 emissions but not N20 emission. The additives increased the ammonium content and electrical conductivity significantly in the final compost. No adverse effect on organic matter degradation or the germination index of the compost was found in the amended treatments. It was recommended that phosphogypsum and DCD could be used in composting for the purpose of reducing NH3 , CH4 and N20 emissions.0ptimal conditions and dose of DCD additive during composting should be determined with different materials and composting systems in further study.

Impact of dicyandiamide on emissions of nitrous oxide,nitric oxide and ammonia from agricultural field in the North China Plain

Nitrous oxide（N_2O）, nitric oxide（NO） and ammonia（NH_3） emissions from an agricultural field in the North China Plain were compared for three treatments during a whole maize growing period from 26 June to 11 October, 2012. Compared with the control treatment（without fertilization, designated as CK）, remarkable pulse emissions of N_2O, NO and NH_3 were observed from the normal fertilization treatment（designated as NP） just after fertilization, whereas only N_2O and NH_3 pulse emissions were evident from the nitrification inhibitor treatment（designated as ND）. The reduction proportions of N_2O and NO emissions from the ND treatment compared to those from the NP treatment during the whole maize growing period were 31% and 100%, respectively. A measurable increase of NH_3 emission from the ND treatment was found with a cumulative NH_3 emission of 3.8 ± 1.2 kg N/ha,which was 1.4 times greater than that from the NP treatment（2.7 ± 0.7 kg N/ha）.

Analysis of trace dicyandiamide in stream water using solid phase extraction and liquid chromatography UV spectrometry

An improved method for trace level quantification of dicyandiamide in stream water has been developed. This method includes sample pretreatment using solid phase extraction.The extraction procedure（including loading, washing, and eluting） used a flow rate of1.0 m L/min, and dicyandiamide was eluted with 20 m L of a methanol/acetonitrile mixture（V/V = 2：3）, followed by pre-concentration using nitrogen evaporation and analysis with high performance liquid chromatography–ultraviolet spectroscopy（HPLC–UV）. Sample extraction was carried out using a Waters Sep-Pak AC-2 Cartridge（with activated carbon）.Separation was achieved on a ZIC-Hydrophilic Interaction Liquid Chromatography（ZIC-HILIC）（50 mm × 2.1 mm, 3.5 μm） chromatography column and quantification was accomplished based on UV absorbance. A reliable linear relationship was obtained for the calibration curve using standard solutions（R^2〉 0.999）. Recoveries for dicyandiamide ranged from 84.6% to 96.8%, and the relative standard deviations（RSDs, n = 3） were below 6.1% with a detection limit of 5.0 ng/m L for stream water samples.

Substitution reaction of dicyandiamide in the presence of phase transfer catalyst

Dicyandiamide (cyanoguanidine) is widely used in the syntheses of melamine and medicines such as barbiturates and guanidine derivatives. However, the substitution reaction of dicyandiamide, particularly the tetra substitution reaction, has not been reported so far. We report here the substitution reaction of dicyandiamide in the presence of phase transfer catalyst.

Mitigating N2O and NO Emissions from Direct-Seeded Rice with Nitrification Inhibitor and Urea Deep Placement

Soil-emitted nitrous oxide(N2O) and nitric oxide(NO) in crop production are harmful nitrogen(N) emissions that may contribute both directly and indirectly to global warming. Application of nitrification inhibitors, such as dicyandiamide(DCD), and urea deep placement(UDP), are considered effective approaches to reduce these emissions. This study investigated the effects of DCD and UDP, compared to urea and potassium nitrate, on emissions, nitrogen use efficiency and grain yields under direct-seeded rice. High-frequency measurements of N2O and NO emissions were conducted using the automated closed chamber method throughout the crop-growing season and during the ratoon crop. Both UDP and DCD were effective in reducing N2O emissions by 95% and 73%, respectively. The highest emission factor(1.53% of applied N) was observed in urea, while the lowest was in UDP(0.08%). Emission peaks were mainly associated with fertilization events and appeared within one to two weeks of fertilization. Those emission peaks contributed to 65%–98% of the total seasonal emissions. Residual effects of fertilizer treatments on the N2O emissions from the ratoon crop were not significant;however, the urea treatment contributed 2%, whereas UDP contributed to 44% of the total annual emissions. On the other hand, cumulative NO emissions were not significant in either the rice or ratoon crops. UDP and DCD increased grain yields by 16%–19% and N recovery efficiency by 30%–40% over urea. The results suggested that the use of DCD and UDP could mitigate N2O emissions and increase grain yields and nitrogen use efficiency under direct-seeded rice condition.

Physical and chemical properties of a durably efficacious ammonium bicarbonate as a fertilizer and its yield-increasing mechanism

A new fertilizer of cocrystal type,known as durably efficacious ammonium bicarbonate(DEAB),has been developed by adding a certain amount of dicyandiamide(DCD)as an ammonia-stabilizing agent to ammonium bearbenate(AB)during the process of its production.As compared with AB,DEAB was found to have a reduction of direct volatilization loss by 53%,a fertilizer availability period prolonged from 35-45 to 90-110 d,and an increase in the rate of nitrogen in fertilizer being utilized by 5.9%-10.2%,and a saving of the amount of fertilizer to be ap-phed by 20%-30%for the same level of yield,or an increase of the crop yield by over 10%for the same level of ni-tregen fertilization;in addition,it was found to show usually a function of promoting the crop to early mature.It can be applied as basal dressing all in one time to soil and thus also used as a labour-saving and crop yield-increasing fertil-izer for is non-mtertillage,plastics film covering and water-saving agriculture.