Soil Science and Plant Nutrition (2008) 54, 644–649 doi: 10.1111/j.1747-0765.2008.00280.x

© 2008 Japanese Society of Soil Science and Plant Nutrition

Blackwell Publishing LtdMitigation options for N2O emission from cornA. Hadi et al.ORIGINAL ARTICLE/SHORT PAPER

Mitigation options for N2O emission from a corn field in Kalimantan, Indonesia

Abdul HADI1, Oslan JUMADI2, Kazuyuki INUBUSHI2 and Kazuyuki YAGI3

1Soil Science Division, Faculty of Agriculture, Lambung Mangkurat University, Banjarbaru 70714, Indonesia, 2Graduate School of Science and Technology, Chiba University, Chiba 271-8510, and 3National Institute for Agro-environmental Sciences, Tsukuba 305-8604, Japan

Abstract

Field experiments were designed to quantify N2O emissions from corn fields after the application ofdifferent types of nitrogen fertilizers. Plots were established in South Kalimantan, Indonesia, and giveneither urea (200 kg ha–1), urea (170 kg ha–1) + dicyandiamide ([DCD] 20 kg ha–1) or controlled-releasefertilizer LP-30 (214 kg ha–1) prior to the plantation of corn seeds (variety BISI 2). Each fertilizer treatmentwas equivalent to 90 kg N ha–1. Plots without chemical N fertilizer were also prepared as a control. Thefield was designed to have three replicates for each treatment with a randomized block design. Nitrousoxide fluxes were measured at 4, 8, 12, 21, 31, 41, 51, 72 and 92 days after fertilizer application (DAFA).Total N2O emission was the highest from the urea plots, followed by the LP-30 plots. The emissions fromthe urea + DCD plots did not differ from those from the control plots. The N2O emission from theurea + DCD plots was approximately one thirtieth of that from the urea treatment. However, fertilizertype had no effect on grain yield. Thus, the use of urea + DCD is considered to be the best mitigationoption among the tested fertilizer applications for N2O emission from corn fields in Kalimantan, Indonesia.

Key words: dicyandiamide, Kalimantan, N2O, soil-pore water inorganic N, soil microbial biomass C and N.

INTRODUCTION

In recent years, concern over global warming andconsequent climate change has led to a worldwideinterest in the processes involved. It is necessary toexamine ways to mitigate greenhouse gas emissions,including nitrous oxide (N2O). Soils contribute 70%to the global budget of N2O emissions (Bouwman1990). In soils, N2O is formed by bacterial actionduring both nitrification and denitrification (Pauland Clark 1996). Watsuji et al. (2003) showed thatfungal denitrification can also produce N2O. Indeedsome studies have demonstrated that nitrificationcan be the main source of N2O emissions from soils(Bremmer and Blackmer 1979; Freney et al. 1979;Inubushi et al. 1996). Similar results have beenreported by Nakajima et al. (1992) from tropicalupland soils.

Nitrification is carried out by a great number ofmicrobes, but the two most classically recognizedgenera of bacteria are Nitrosomonas and Nitrobacter.Nitrosomonas as well as Nitrosospira and otherammonium oxidizers convert to andNitrobacter facilitates a further step by converting

to (Bremmer and Blackmer 1981). TheN2O is released as a by-product of nitrification. How-ever, more information is required to mitigate N2Oemissions, especially from tropical soils.

In tropical agricultural soils, nitrogen (N) fertiliza-tion is often considered to be the main source of N2Oemissions, as in temperate soils. Crill et al. (2000)found that N2O emissions from fertilized plots wereapproximately fivefold greater than those from unferti-lized plots in Costa Rican soils. Mosier and Delgado(1997) reported that nearly 4% of applied N was lostin the form of N2O in Puerto Rican soils. Therefore,efficient agricultural practices, including the use ofappropriate N fertilizer, are needed if the N2O emissionsfrom tropical soils are to be minimized.

In South Kalimantan, Indonesia, urea is the mostwidely used N fertilizer, accounting for more than 95%of N application (Dewan Ketahanan Pangan Kalsel

Correspondence: A. HADI, Soil Science Division, Faculty ofAgriculture, Lambung Mangkurat University, Banjarbaru 70714,Indonesia. Email: atakhadi@hotmail.comReceived 1 October 2007.Accepted for publication 29 February 2008.

NH4+ NO2

−

NO2− NO3

−

Mitigation options for N2O emission from corn 645

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2002). Urea is mainly applied to commonly cultivatedannual crops, such as paddy, corn and soybean. Khalilet al. (2002) measured N2O emissions during an annualgroundnut–corn crop rotation on the Malaysian penin-sula and found the highest N2O emissions during thecorn part of the cropping sequence. However, there areno reports regarding the effect of urea application andmitigation options on the emission of N2O from cornfields in Kalimantan or from other Indonesian regions.

Dicyandiamide (DCD) is widely used in temperateregions to moderate N loss by leaching. In addition,the effectiveness of DCD in reducing N2O emissionshas been reported mostly from temperate zones(Amberger 1989; Di and Cameron 2006). Dicyandi-amide is made by dimerization of cyanamide andcontains approximately 67% N (Amberger 1989).Many different types of controlled-release fertilizerswith various characteristics have been developed inJapan, including LP-30, a urea fertilizer coated withthermoplastic polyolifin (Shoji and Gandeza 1992).However, the possible uses of these sources of N incorn fields in the tropics are poorly understood.Therefore, this study was designed to quantify N2Oemissions from a tropical agricultural field after theapplication of different types of N fertilizers. Theobjective of the study was to determine which fertiliz-ers, if any, can mitigate N2O emissions from corn fieldsin Kalimantan, Indonesia.

MATERIALS AND METHODS

Twelve plots measuring 4 m × 5 m each were estab-lished in the Cempaka sub-district, South Kalimantan,

Indonesia (03°28′45″S; 114°50′47″E). The plots wereploughed as per the farmers’ practice. The soil usedwas an Ultisol. The properties of the plough layer soilare given in Table 1.

Lime and cow dung were applied at rates of 2 and4 ton ha–1, respectively, 3 weeks before planting. Theplots received either urea (200 kg ha–1), urea(170 kg ha–1) + DCD (20 kg ha–1) or controlled-releasefertilizer LP-30 (214 kg ha–1); each fertilizer treatmentwas equivalent to 90 kg N ha–1. Plots without N ferti-lizer were used as control plots. The controlled-releasefertilizer, LP-30, is urea coated with thermoplasticspolyolefin (Shoji and Gandeza 1992). The number“30” indicates that the fertilizer is designed to release80% of the N at 25°C in the 30 days after application.Dyciandiamide (H2NC(=NH)NHCN) is a nitrificationinhibitor that blocks the activity of ammonia mono-oxygenase enzyme, thus inhibiting the oxidation ofammonia to nitrite (Sylvia et al. 2005).

All N fertilizers were applied by top dressing once,on the day of planting, except for the urea treatment.Two-thirds of the urea was applied on the day ofplanting and the remaining one-third was applied35 days after planting using a similar method to theother N fertilizers. The field was designed to have threereplicates for each treatment using a randomized blockexperimental design. Super phosphate, 250 kg ha–1

(39.3 kg P ha–1), and KCl, 100 kg ha–1 (39.3 kg K ha–1),were applied as basal fertilizers. Basal fertilizers wereplaced 10 cm from a plant at a depth of 5 cm as a bandapplication on the day of planting.

Corn seeds (variety BISI 2) were planted (9 November2004) at a rate of three seeds per hole, with a spacingof 20 cm × 75 cm in a west–east orientation. Pest anddisease controls were carried out when necessary as perthe farmers’ practice until harvest. Harvest was donemanually by picking the ear of the stem and removingthe grain. The plants were cut at the soil surface anddried at 70°C for 48 h to measure above-groundbiomass.

Nitrous oxide flux (from the soil surface to theatmosphere) was determined at 4, 8, 12, 21, 31, 41,51, 72 and 92 days after fertilizer application (DAFA)using a closed chamber as described by Hadi et al.(2000). In brief, the chamber was constructed of apolyvinylchloride pipe (21 cm in diameter and 14 cm inlength) that was inserted into the band of fertilizer inbetween the plants. Gas samples (inside the chamber)were collected by inserting a 35 mL syringe into a tubeattached to the chamber and then sucking the air out.Four gas samples were collected from each chamber at0, 5, 10 and 15 min after the enclosure was established.The concentration of N2O in each chamber was meas-ured using a gas chromatograph equipped with an

Table 1 Soil properties of the plough layer of the soils used

Properties Value

Sand (%) 66.4Loam (%) 24.0Clay (%) 9.6Organic C (g kg–1) 19.7Total N (g kg–1) 1.3Total P (mg kg–1) 11.5Total K (mg kg–1) 9.6pH 4.6Cation exchange capacity (c(+)mol kg–1) 29.7

(mg kg–1) 0.02 (mg kg–1) 0.04

Viable bacteria (×106 c.f.u. g–1) 2.2Viable fungi (×105 c.f.u. g–1) 3.0Ammonium oxidizer (×102 MPN g–1) 1.4Nitrite oxidizer (×102 MPN g–1) 1.4

MPN, most probable number.

NH4+

NO3−

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© 2008 Japanese Society of Soil Science and Plant Nutrition

electron capture detector (Shimadzu, Kyoto, Japan).The flux was then calculated from the temporalincrease in gas concentration inside the chamberper unit time (Yagi 1997).

Along with the gas flux measurements on days whenN transformations were expected to be high (i.e. 31and 51 days after fertilizer application), soil-pore waterwas collected by inserting a water sampler (DAIKI-8390; Daiki Physichochemical Company, Tokyo, Japan)to a soil depth of 25 cm at the center of four hills ofcorn plants and sucking water into a 50 mL syringe.The water was then analyzed for inorganic N concen-trations (i.e. and ). The wasreduced to nitrite by hydrazine sulfate under alkalineconditions and then analyzed colorimetrically (Hayashiet al. 1997). The was determined colorimet-rically using a modified Berthelot reaction (Page et al.1982).

Soil samples were taken up to a depth of 30 cm at 4and 41 DAFA (when N transformations were expected

to be high) and analyzed for inorganic N concentrations,urease enzyme activity and microbial biomass C and N.The and concentrations were determinedby extraction of the soil with 1 mol L–1 KCl at anextractant : sample ratio of 10:1 (v/w). The extractswere filtered through Whatman 42 ash-free filter paper(Whatman International, Midstone, UK). Measure-ments were carried out colorimetrically as describedpreviously for the soil-pore water. Urease enzyme activ-ities were estimated using the method described byPage et al. (1982), while biomass C and N were estimatedusing the chloroform fumigation–extraction methoddescribed by Inubushi et al. (1989).

All statistical analyses were carried out using SPSS11.0 software for Windows (SSPS, Chicago, IL, USA).The frequency distributions of all data were first testedfor normality using Kolmogorov–Smirnov tests. If thedata were normally distributed, differences betweentreatments were determined by anova and least signifi-cant differences (LSD) tests. A simple linear correlationbetween the measured parameters was carried out.Results were considered significant at P < 0.05.

RESULTS

Patterns of N2O emissions were affected by the type offertilizer (Fig. 1). The urea plots started to releaseconsiderable amounts of N2O at 31 DAFA and continuedto release until 41 DAFA, which was 6 days after topdressing. The LP-30 plots released considerableamounts of N2O at 41 DAFA. In contrast, N2O emis-sion from the urea + DCD and control plots remainedlow during the crop season.

Total N2O emission during the cultivation periodwas highest from the urea plots, followed by the LP-30plots. Emissions from the urea + DCD plots did notdiffer significantly from the control plots (Table 2). TheN2O emission from the urea + DCD plots was approxi-mately one thirtieth of that from the urea treatment.

Fertilizer type affected the concentration,but not the concentration of soil-pore water

Figure 1 Nitrous oxide (N2O) emissions as affected byfertilizer application in a corn field in South Kalimantan.Error bars are standard deviation of the mean. DCD,dicyandiamide; LP-30, controlled-release fertilizer.

Table 2 Nitrous oxide emission, number of ear of stem, grain yield and above-ground biomass as affected by fertilizer type inSouth Kalimantan

TreatmentN2O emission

(mg N m–2 crop season–1)Number of ear of stem

(no. ha–1)Grain yield (ton ha–1)

Above-ground biomass (ton ha–1)

Control 21.2c (20.4) 62,220a (10,184) 5.02a (1.14) 10.13b (1.78)Urea 691.7a (109.7) 82,220a (16,778) 6.30a (1.83) 15.12b (2.28)Urea + DCD 21.1c (9.0) 77,780a (26,243) 5.64a (1.79) 21.43ab (1.82)LP-30 57.3b (53.5) 66,620a (37,119) 6.33a (3.84) 25.28a (3.96)

Means followed by the same letters are not significantly different at P < 0.05. Values in parentheses indicate standard deviation. DCD, dicyandiamide; LP-30, controlled-release fertilizer.

NO -N3− NH -N4

+ NO -N3−

NH -N4+

NO3− NH4

+

NH -N4+

NO -N3−

Mitigation options for N2O emission from corn 647

© 2008 Japanese Society of Soil Science and Plant Nutrition

(Fig. 2). At 31 DAFA, the lowest of soil-porewater was observed in the urea plots, which did notdiffer from the control and urea + DCD plots. Thehighest of soil-pore water was observed in theLP-30 plots. At 51 DAFA, the lowest in soil-porewater was observed in the urea + DCD plots, which didnot differ from the LP-30 and control plots. The

highest of soil-pore water was observed in theurea plots. The proportions of in inorganic Nwere generally more than in soil-pore water.

Fertilizer type affected the soil concentra-tion, but not the concentration at 4 DAFA(Fig. 3). Soil concentration in the urea plotswas the highest at 4 DAFA. The lowest wasdetected in the control plot at 4 DAFA, when theammonium concentration was negligible. No significantdifferences in soil inorganic N were recorded in theother treatments.

The type of fertilizer had no effect on either ureaseenzyme activity or microbial biomass C and N at thecorn harvest stage. Urease enzyme activity ranged from18.7 ± 9.4 (mean ± standard deviation) μg N g–1 soil 2 h–1

in the urea plots to 59.8 ± 9.3 μg N g–1 soil 2 h–1 in thecontrol plots. The microbial biomass C ranged from62.2 ± 21.6 mg C kg–1 soil in the control plots to211.5 ± 70 mg C kg–1 soil in the urea plots, whilebiomass N ranged from 0.1 mg N kg–1 soil in thecontrol plots to 1.1 mg N kg–1 soil in the urea plots.

Neither number of ear of stem nor grain yield wasaffected by fertilizer application (Table 2). Above-groundplant biomass was the highest in the LP-30 plots,which was not different from that in the urea + DCDplots. The lowest above-ground plant biomass wasobserved in the control plots.

There was a significant correlation between the contents of soil-pore water and N2O flux at 51

DAFA (r = 0.92). Total N2O emission (i.e. over the4–92-day period) was also significantly correlatedwith gas fluxes at 41 (r = 0.99), 51 (r = 0.88) and 92(r = 0.66) DAFA. The total emission (Y, mg N m–2)can be estimated by N2O fluxes at 41, 51 or 92 DAFAusing the following regression equations: Y = 298.25 ×flux at 41 DAFA + 27.13, Y = 1,930.5 × flux at 51DAFA + 38.913 and Y = 4,631.1 × flux at 92 DAFA +109.1, respectively. However, neither soil-pore waterN, soil N nor N2O flux were correlated with plantproduction.

DISCUSSION

The patterns of N release are specific for a particularfertilizer when the soil properties and conditions aresimilar among the different fertilizer treatments. It islikely that the different patterns of N2O emissionsobserved in the current study can be attributed to Nrelease patterns from the different treatments. Urea isconsidered to be a fast-release N fertilizer and startedto release considerable amounts of N2O earlier than theother fertilizers (i.e. 21 DAFA; Fig. 1), although activenutrient uptake by corn suppressed the N2O emissionsafter fertilizer application.

Figure 2 Inorganic N contents of soil-pore water in SouthKalimantan. Different lowercase letters indicate significantdifferences in nitrate concentrations among the treatments atP < 0.05. Different capital letters indicate significant differencesin ammonium concentrations among the treatments atP < 0.05. Error bars are standard deviation of the mean.DCD, dicyandiamide; LP-30, controlled-release fertilizer.

NH -N4+

Figure 3 Inorganic soil N contents in South Kalimantan.Different lowercase letters indicate significant differences innitrate concentrations among the treatments at P < 0.05.Different capital letters indicate significant differences inammonium concentrations among the treatments at P < 0.05.Error bars are standard deviation of the mean. DCD,dicyandiamide; LP-30, controlled-release fertilizer.

NH -N4+

NH -N4+

NH -N4+

NH -N4+

NO -N3−

NH -N4+

NO -N3−

NH -N4+

NH -N4+

NH -N4+

648 A. Hadi et al.

© 2008 Japanese Society of Soil Science and Plant Nutrition

It appears that the release of N from LP-30 in thisstudy met the N needs of the corn. This was also reflectedin the N2O pattern, which remained negligible until 41DAFA when some N2O were released from the plot.

The presence of DCD seemed to delay the formationof N2O. This may be because of an inhibition effect onnitrification processes. The result obtained in thepresent study, that N2O from the urea + DCD treatmentwas lower than the other N fertilizer treatments, hasalso been reported previously by Mosier et al. (1996)and Bronson and Singh (1995). Nitrogen loss in theform of N2O from the urea + DCD plots was only onethirtieth of that from the urea plot, suggesting that theuse of urea + DCD was effective in minimizing N2Oemissions from corn fields in the tropics.

The concentrations of inorganic N in the soil mayalso be explained by the release patterns of the Ncontained in each fertilizer. Urea in the urea plots waspossibly hydrolyzed soon after the application of urea,and resulted in a flush of into the soil (Fig. 3)with relatively low cation exchange capacity (Table 1).In the urea + DCD and LP-30 plots, the release of

was delayed as a result of the protection effect ofDCD or the coating material of LP-30 (Paul and Clark1996; Shoji and Gandeza 1992).

A significant positive correlation between total N2Oemission and concentrations in soil-pore watersuggest that soil-pore water plays an important rolein N2O formation and emission. Yan et al. (2000) alsoreported a strong relationship between con-centration in soil water and N2O emissions from paddyfields.

The lack of statistical significance between soil orwater parameters and plant production (data notshown) indicated that the plant had not been deter-mined only by the observed parameters. Light density,temperature and precipitation are major environmentalfactors controlling plant growth and development. Similarenvironmental factors at the experimental sites mightresult in similar grain yields among treatments (Table 2).

Significant correlations between total N2O emissionand N2O fluxes at 41, 51 and 92 DAFA suggest that

the N2O fluxes at 41, 51 and 92 DAFA are an impor-tant part of the measurements to determine total N2Oemissions from corn fields in the tropics. This might berelated to the generative growth of corn when less Nwas taken up by the plants. Thus, any additionalmitigation option should be done on these days if thetotal N2O emission is to be reduced.

Emission indices (ratio of greenhouse gas emissionover crop production) should be assessed when decid-ing on agricultural technology (Kimura et al. 1991;Nugroho et al. 1994). This notion is in line with themitigation concept, which is defined as a reduction ingas emission without any reduction in crop production.Considering the emission indices, the presence of DCDalong with urea lowered the value compared with ureaalone (Table 3). This suggests that the addition of DCDcan obtain the same corn product as urea while reducingthe environmental pollution caused by N2O emission.The use of urea + DCD also results in labor cost reduc-tion with a single basal application. Moreover, DCDcan minimize leaching losses, avoid stressand the associated increased susceptibility of the plantto fungal infection (Amberger 1989). Therefore, the useof urea + DCD can be considered to be the best mitiga-tion option for N2O emission from corn fields inKalimantan, Indonesia.

ACKNOWLEDGMENTS

This study was managed under the project “SSCP-3a:Development and evaluation of mitigation technologiesfor CH4 and N2O emissions from agroecosystems”supported by the Global Environmental Fund, theMinistry of the Environment, Government of Japan(B-S-2-3a). This paper was presented at the “InternationalWorkshop on Monsoon Asia Agricultural GreenhouseGas Emissions (MAGE-WS)”, 7–9 March 2006, Tsukuba,Japan. We thank Dr[i1]. ME. Tachibana of ChissoasahiFertilizer Co., Ltd. for providing the fertilizer tested, andMiss ER Terawatt Magnate and Miss Witan Dalianisof Lambung Mangkurat University for help with thesample collections.

Table 3 Nitrous oxide emission indices

TreatmentGram N2O per 1,000

ear of stemGram N2O per ton

grain yieldGram N2O per ton

plant biomass

Control 3.8b (3.7) 47.6b (44.0) 22.5b (21.0)Urea 88.3a (31.2) 1,158.3a (386.3) 473.0a (153.3)Urea + DCD 3.0b (2.0) 44.2b (32.6) 10.0b (4.4)LP-30 15.6b (16.8) 163.6b (197.2) 25.3b (25.5)

Means followed by the same letters are not significantly different at P < 0.05. Values in parentheses indicate standard deviation. DCD, dicyandiamide; LP-30, controlled-release fertilizer.

NH4+

NH4+

NH -N4+

NH -N4+

NO3− NO3

−

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© 2008 Japanese Society of Soil Science and Plant Nutrition

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